Introduction De nombreuses études indiquent que la prématurité, qui représente 8 % des naissances, est associée à des indices précoces de dysfonction vasculaire, d’élévation de la pression sanguine et de survenue de diabète de type 2. Les enfants nés prématurément sont plus sujets aux blessures oxydatives de par l’immaturité de leurs défenses antioxydantes et de leur exposition à des situations pro-oxydantes (exposition à l’air ambiant, à un supplément d’oxygène, ou à une exposition aux infections). Cependant, les conséquences à long terme des blessures oxydatives induites par une exposition à l’oxygène en période périnatale restent méconnues. Le but de ce doctorat a été de mettre en évidence certains mécanismes pouvant relier les dommages de la prématurité induits par l’oxygène, et le risque à long terme de développer des maladies cardiovasculaires et métaboliques dans le concept global d’une programmation développementale de l’hypertension et des pathologies reliées au syndrome métabolique. Matériels et méthodes Des ratons Sprague-Dawley (SD) ont été exposés à 80 % O2 (O2) vs air ambiant (AA) du 3ème au 10ème jour de vie. Concernant les paramètres cardiovasculaires, nous avons mesuré au cours de la croissance, la pression sanguine à la queue (de la 4ème semaine à la 15ème semaine) et à l’âge adulte : la réactivité vasculaire à l’angiotensine II (AngII) et au carbachol (ex vivo, carotides) avec ou sans le tempol; la production d’oxyde nitrique (NO) en présence ou non L-arginine et de L-sépiaptérine (aorte, immunohistochimie) ainsi que l’expression de la nitric oxyde synthase endothéliale (eNOS) (aorte, immunohistochimie et western blot); le stress oxydant vasculaire (aorte, chemiluminescence) par la mesure de la production d’anions superoxide en présence ou non des inhibiteurs de la nicotinamide-adenine-dinucleotide-phosphate (NADPH oxydase) et de la nitric oxyde synthase endotheliale (eNOS), l’apocynine, et N-nitro-L-arginine methyl ester (L-NAME) respectivement, ainsi que le stress oxydant circulant par la mesure des niveaux plasmatiques de malondialdéhyde (MDA, HPLC); la densité microvasculaire a été évaluée au niveau du muscle tibial antérieur, immunohistochimie); la vitesse d’onde pulsée (VOP) (entre la valve aortique et juste avant la bifurcation ilio-fémorale) a été mesurée par ultrason; le nombre de néphrons a été compté par digestion acide. L’ontogenèse de la plupart de ces mécanismes a été regardée à l’âge de 4 semaines. Concernant les paramètres métaboliques, le poids a été mesuré au cours de la croissance. À l’âge adulte, la composition corporelle et la tolérance au glucose ont été évaluées. Résultats À l’âge de 4 semaines, aucune différence n’a été observée dans la pression sanguine, la réactivité vasculaire et le stress oxydant, mais chez les rats O2 vs AA, la densité microvasculaire est moindre, et des changements histologiques suggèrent la présence d’une rigidité artérielle augmentée. À l’âge adulte chez les rats O2 vs AA (n = 6-8 /groupe) : i) les pressions sanguines systoliques et diastoliques sont augmentées; ii) la réactivité vasculaire à l’AngII est augmentée et celle au carbachol est diminuée, le tempol prévient ces dysfonctions; iii) la production de NO est plus faible au niveau basal et après stimulation par le carbachol, mais est restaurée après la pré-incubation avec L-arginine et L-sépiaptérine; iv) l’expression d’eNOS est diminuée par immunohistochimie et augmentée par western blot; v) les niveaux d’anions superoxide, au niveau basal et en réponse à l’AngII, sont augmentés et sont induits par la NADPH oxydase et le non-couplage d’eNOS; vi) les niveaux plasmatiques de MDA sont augmentés; vii) La densité microvasculaire est moindre; viii) la VOP est augmentée; ix) le nombre de néphrons par rein est réduit; x) le poids est plus faible au cours de la croissance et un catch up est observé à l’âge adulte; la composition corporelle n’est pas différente entre les groupes; xi) la tolérance au glucose est diminuée. Conclusion Ces résultats supportent l’hypothèse d’une programmation développementale des maladies cardiovasculaires et métaboliques à l’âge adulte à la suite d’un stress hyperoxique néonatal. / Introduction Many studies showed that prematurity, which represents 8 % of birth, is associated with early indices of vascular dysfunction, increased blood pressure and Type 2 diabetes. Prematurity babies are more susceptible to oxidative injury, consequence of the immaturity of their antioxidant defences, and exposure to pro-oxidant situations (oxygen supplementation, infection). However, the long-term consequences of oxidative injury induced by oxygen exposure in the neonatal period are unknown. The aim of these PhD studies was to unravel some mechanisms that might underlie the damage induced by oxygen and the long-term risk of developing vascular and metabolic diseases in the overall concept of developmental programming of hypertension and metabolic syndrome-related diseases. Materials and methods Sprague-Dawley pups were kept with their mother in 80 % O2 (O2) or room air (RA) from day 3 to 10 of life. Cardiovascular parameters, tail blood pressure was measured between 4 and 15 weeks of life. In adulthood : vascular reactivity (ex vivo carotid rings) to angiotensine II (AngII) and carbachol with and without tempol was studied; studies of nitric oxide (NO) production with and without L-arginine and L-sépiaptérine (aorta, immunohistochemistry) and endothelial nitric oxide synthase expression (eNOS; aorta, immunohistochemistry, western blot) were performed; vascular oxidative stress (aorta, using chemiluminescence) by measuring superoxide anion production with and without inhibitors of nicotinamide-adenine-dinucleotide-phosphate (NADPH oxydase) and nitric oxyde synthase endotheliale (eNOS), apocynin and N-nitro-L-arginine methyl ester (L-NAME) respectively, and circulating oxidative stress by measuring the plasma levels of malondialdéhyde (MDA, HPLC) were evaluated; microvascular density was assessed on tibialis anterior muscle sections; pulse wave velocity (PWV) was measured by ultrasound, between aortic valve and ilio-femoral bifurcation; nephrons were counted after hydrochloric acid digestion. The main observations were also evaluated at 4 weeks of age. Metabolic parameters: body weight has been measured during the growth. In adulthood, body composition, glucose tolerance were evaluated. Results A 4 weeks of age, no difference was observed regarding blood pressure, vascular reactivity, and oxidative stress indices, but in rats O2 vs. RA (n = 6-8 /group), microvascular rarefaction and histological changes suggesting enhanced vascular stiffness were present. To adulthood, rats O2 vs. RA (n = 6-8/group) : i) systolic and diastolic blood pressures are increased; ii) vascular reactivity to Ang II is increased and to carbachol is decreased, these dysfunction were totally abolished by co-incubation of the vessel rings with tempol; iii) NO-production is decreased in basal condition and after carbachol stimulation, but is restored after pre-incubation of aorta sections with L- arginine and L-sépiaptérine; iv) eNOS expression is decreased by immunohistochemistry but increased by western blot; v) vascular superoxide anion levels are increased in basal condition, after AngII stimulation and this is mediated by NADPH oxydase and eNOS uncoupling; vi) the plasma levels of MDA are increased; vii) microvascular density is decreased; viii) PWV is increased; ix) nephron count per kidney is decreased; x) body weight is less during growth, but a catch up is observed in adulthood, body composition is similar; xi) the glucose tolerance is decreased in adults. Conclusion These results support the hypothesis of developmental programming of vascular and metabolic diseases in adulthood, after exposure to hyperoxic stress in the neonatal period. / Thèse réalisée dans le cadre d'une cotutelle entre l'Université de Montréal et l'Université d'Auvergne en France

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / As doenças cardiovasculares estão entre as principais causas de mortalidade em muitos países. O sistema nervoso autônomo e a função endotelial constituem mecanismos centrais no desenvolvimento e progressão de doenças cardiovasculares. A função autonômica e a reatividade vascular podem estar alteradas em indivíduos com maior risco para doença cardiovascular, como indivíduos com história familiar de primeiro grau de diabetes tipo 2 (HFDM2) e indivíduos com polimorfismo 894G>T da enzima óxido nítrico sintase endotelial (eNOS). Os objetivos dos três artigos apresentados na tese foram: artigo I. Investigar a influência da HFDM2 na modulação autonômica cardíaca em ausência de desordens metabólicas concomitantes; artigo II. Investigar a influência da HFDM2 na reatividade vascular em ausência de desordens metabólicas concomitantes e, artigo III. Investigar a influência do polimorfismo 894G>T no efeito de uma sessão de exercício dinâmico máximo na reatividade vascular. Foram recrutados indivíduos saudáveis com e sem HFDM2 para os artigos I e II. A variabilidade da frequência cardíaca (VFC) foi determinada através da análise espectral de um registro de intervalos RR durante 10 minutos na posição supina (artigo I) e a reatividade vascular durante a hiperemia reativa através da pletismografia de oclusão venosa (artigo II). Para a realização do artigo III, foram recrutados indivíduos saudáveis com e sem o polimorfismo 894G>T da eNOS. O protocolo consistiu na determinação da reatividade vascular basal e durante a hiperemia reativa, o qual eram realizados pré, 10, 60 e 120 minutos após um teste de esforço cardiopulmonar máximo. Os indivíduos com HFDM2 apresentaram maiores valores para variáveis antropométricas e metabólicas e uma menor VFC (artigo I) e reatividade vascular (artigo II) quando comparados com o grupo-controle (p<0,05). Em seguida, os grupos foram emparelhados para essas variáveis consideradas capazes de alterar a VFC e a reatividade vascular e nenhuma diferença significativa foi encontrada entre os grupos nos artigos I e II (p>0,05). Foi realizada análise de correlação simples, sendo que as variáveis que apresentaram significância estatística foram submetidas à análise de regressão múltipla. Esta identificou colesterol (P=0,014) e triglicerídeos (P=0,014) como preditores independentes da VFC (modelo r2=0,16; P<0,001) e insulina (P<0,05) e razão cintura-quadril (P<0,05) como preditores independentes da reatividade vascular (modelo r2=0,22; P=0,006). No artigo III, não foram observadas diferenças entre os indivíduos com e sem o polimorfismo 894G>T em relação as características antropométricas, metabólicas e hemodinâmicas e medidas de fluxo sanguíneo antes do exercício dinâmico máximo (P>0,05). Os indivíduos polimórficos apresentaram menor reatividade vascular independente do tempo (efeito do grupo P=0,019) e a análise de post-hoc revelou que os indivíduos polimórficos apresentavam valor menor apenas no momento 120 minutos (P=0,022) quando comparados com indivíduos sem o polimorfismo. Estes achados sugerem que indivíduos com HFDM2, em ausência de desordens metabólicas concomitantes, não apresentam alteração da modulação autonômica cardíaca e de reatividade vascular. Em adendo, indivíduos com polimorfismo 894G>T, têm menor reatividade vascular após um sessão de exercício, denotando a presença de disfunção vascular. / Cardiovascular diseases are among the leading causes of mortality in many countries. The autonomic nervous system and the endothelial function are central mechanisms in the development and progression of cardiovascular diseases. The autonomic function and vascular reactivity may be altered in subjects with higher risk for cardiovascular disease, as subjects with family history of first-degree relatives of type 2 diabetes (FDRs), and subjects with the 894G>T polymorphism of the endothelial nitric oxide synthase (eNOS). The aims of these three papers presented at this thesis were: paper I. To investigate the influence of FDR on cardiac autonomic modulation in the absence of concomitant metabolic disorders; paper II. To investigate the influence of FDR on vascular reactivity in the absence of concomitant metabolic disorders; paper III. To investigate the influence of the 894G>T polymorphism on the effect of a single bout of maximal dynamic exercise on vascular reactivity. Healthy subjects with and without FDRs were recruited for the paper I and II. The heart rate variability (HRV) was determined by spectral analysis of inter-beat intervals recorded during 10 min in the supine position (paper I) and vascular reactivity during the reactive hyperemia by venous occlusion plethysmography (paper II). For the paper III, healthy subjects with and without the 894G>T polymorphism of the eNOS were recruited. The protocol consisted of vascular reactivity assessment at baseline and during reactive hyperemia, which were performed pre, 10, 60 and 120 min after a maximal cardiopulmonary exercise test. The FDRs exhibited higher values for anthropometric and metabolic variables and lower values for HRV (paper I), and vascular reactivity (paper II) when compared to the control subjects (p<0.05). After matching the groups for variables, that are known to alter HRV and vascular reactivity, no significant difference was observed between groups in the paper I and II (p>0.05). Following single correlation analysis, only the variables with statistical significance were submitted to multiple regression analysis. This identified cholesterol (P=0.014) and triglycerides (P=0.014) as significant predictors of HRV (model r2=0.16; p<0.001), and insulin (P<0.05) and waist-to-hip ratio (P<0.05) as independent predictors (model r2=0.22; P=0.006). There were no differences between the subjects with and without the 894G>T polymorphism concerning anthropometric, metabolic, and hemodynamic characteristics, and blood flow measurements before maximal dynamic exercise (P>0.05), in the paper III. The polymorphic subjects presented lower vascular reactivity regardless of time (P=0.019 for group main effect), and post-hoc analysis revealed that polymorphic subjects had lower values only at the 120 min measurement (P=0.022) when compared with subjects without the polymorphism. These findings suggest that FDRs, in the absence of concomitant metabolic disorders, does not impair cardiac autonomic modulation and vascular reactivity. Furthermore, subjects with the 894G>T polymorphism had lower vascular reactivity after a single bout of exercise, denoting the presence of vascular dysfunction.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / As doenças cardiovasculares estão entre as principais causas de mortalidade em muitos países. O sistema nervoso autônomo e a função endotelial constituem mecanismos centrais no desenvolvimento e progressão de doenças cardiovasculares. A função autonômica e a reatividade vascular podem estar alteradas em indivíduos com maior risco para doença cardiovascular, como indivíduos com história familiar de primeiro grau de diabetes tipo 2 (HFDM2) e indivíduos com polimorfismo 894G>T da enzima óxido nítrico sintase endotelial (eNOS). Os objetivos dos três artigos apresentados na tese foram: artigo I. Investigar a influência da HFDM2 na modulação autonômica cardíaca em ausência de desordens metabólicas concomitantes; artigo II. Investigar a influência da HFDM2 na reatividade vascular em ausência de desordens metabólicas concomitantes e, artigo III. Investigar a influência do polimorfismo 894G>T no efeito de uma sessão de exercício dinâmico máximo na reatividade vascular. Foram recrutados indivíduos saudáveis com e sem HFDM2 para os artigos I e II. A variabilidade da frequência cardíaca (VFC) foi determinada através da análise espectral de um registro de intervalos RR durante 10 minutos na posição supina (artigo I) e a reatividade vascular durante a hiperemia reativa através da pletismografia de oclusão venosa (artigo II). Para a realização do artigo III, foram recrutados indivíduos saudáveis com e sem o polimorfismo 894G>T da eNOS. O protocolo consistiu na determinação da reatividade vascular basal e durante a hiperemia reativa, o qual eram realizados pré, 10, 60 e 120 minutos após um teste de esforço cardiopulmonar máximo. Os indivíduos com HFDM2 apresentaram maiores valores para variáveis antropométricas e metabólicas e uma menor VFC (artigo I) e reatividade vascular (artigo II) quando comparados com o grupo-controle (p<0,05). Em seguida, os grupos foram emparelhados para essas variáveis consideradas capazes de alterar a VFC e a reatividade vascular e nenhuma diferença significativa foi encontrada entre os grupos nos artigos I e II (p>0,05). Foi realizada análise de correlação simples, sendo que as variáveis que apresentaram significância estatística foram submetidas à análise de regressão múltipla. Esta identificou colesterol (P=0,014) e triglicerídeos (P=0,014) como preditores independentes da VFC (modelo r2=0,16; P<0,001) e insulina (P<0,05) e razão cintura-quadril (P<0,05) como preditores independentes da reatividade vascular (modelo r2=0,22; P=0,006). No artigo III, não foram observadas diferenças entre os indivíduos com e sem o polimorfismo 894G>T em relação as características antropométricas, metabólicas e hemodinâmicas e medidas de fluxo sanguíneo antes do exercício dinâmico máximo (P>0,05). Os indivíduos polimórficos apresentaram menor reatividade vascular independente do tempo (efeito do grupo P=0,019) e a análise de post-hoc revelou que os indivíduos polimórficos apresentavam valor menor apenas no momento 120 minutos (P=0,022) quando comparados com indivíduos sem o polimorfismo. Estes achados sugerem que indivíduos com HFDM2, em ausência de desordens metabólicas concomitantes, não apresentam alteração da modulação autonômica cardíaca e de reatividade vascular. Em adendo, indivíduos com polimorfismo 894G>T, têm menor reatividade vascular após um sessão de exercício, denotando a presença de disfunção vascular. / Cardiovascular diseases are among the leading causes of mortality in many countries. The autonomic nervous system and the endothelial function are central mechanisms in the development and progression of cardiovascular diseases. The autonomic function and vascular reactivity may be altered in subjects with higher risk for cardiovascular disease, as subjects with family history of first-degree relatives of type 2 diabetes (FDRs), and subjects with the 894G>T polymorphism of the endothelial nitric oxide synthase (eNOS). The aims of these three papers presented at this thesis were: paper I. To investigate the influence of FDR on cardiac autonomic modulation in the absence of concomitant metabolic disorders; paper II. To investigate the influence of FDR on vascular reactivity in the absence of concomitant metabolic disorders; paper III. To investigate the influence of the 894G>T polymorphism on the effect of a single bout of maximal dynamic exercise on vascular reactivity. Healthy subjects with and without FDRs were recruited for the paper I and II. The heart rate variability (HRV) was determined by spectral analysis of inter-beat intervals recorded during 10 min in the supine position (paper I) and vascular reactivity during the reactive hyperemia by venous occlusion plethysmography (paper II). For the paper III, healthy subjects with and without the 894G>T polymorphism of the eNOS were recruited. The protocol consisted of vascular reactivity assessment at baseline and during reactive hyperemia, which were performed pre, 10, 60 and 120 min after a maximal cardiopulmonary exercise test. The FDRs exhibited higher values for anthropometric and metabolic variables and lower values for HRV (paper I), and vascular reactivity (paper II) when compared to the control subjects (p<0.05). After matching the groups for variables, that are known to alter HRV and vascular reactivity, no significant difference was observed between groups in the paper I and II (p>0.05). Following single correlation analysis, only the variables with statistical significance were submitted to multiple regression analysis. This identified cholesterol (P=0.014) and triglycerides (P=0.014) as significant predictors of HRV (model r2=0.16; p<0.001), and insulin (P<0.05) and waist-to-hip ratio (P<0.05) as independent predictors (model r2=0.22; P=0.006). There were no differences between the subjects with and without the 894G>T polymorphism concerning anthropometric, metabolic, and hemodynamic characteristics, and blood flow measurements before maximal dynamic exercise (P>0.05), in the paper III. The polymorphic subjects presented lower vascular reactivity regardless of time (P=0.019 for group main effect), and post-hoc analysis revealed that polymorphic subjects had lower values only at the 120 min measurement (P=0.022) when compared with subjects without the polymorphism. These findings suggest that FDRs, in the absence of concomitant metabolic disorders, does not impair cardiac autonomic modulation and vascular reactivity. Furthermore, subjects with the 894G>T polymorphism had lower vascular reactivity after a single bout of exercise, denoting the presence of vascular dysfunction.

Objetivos: Avaliar as médias das velocidades e Índices Doppler das Artérias Cerebrais Médias (ACM) e Oftálmicas (AO) de tabagistas conforme o tempo de consumo do cigarro em função do sexo. Avaliar as relações entre a ACM e a AO. Métodos: Utilizou-se o método Doppler para a avaliação do Pico de Velocidade Sistólica (PSV), Velocidade Diastólica Final (VDF) e Velocidade Média (VM) na ACM e na AO. Foi realizada a coleta da VM na Artéria Carótida Interna (ICA) para a realização do Índice de Lindegaard (IL). Os Índices de Resistência (IR) e de Pulsatilidade (IP) também foram avaliados em ambos os vasos. O Segundo Pico de Velocidade Sistólica (P2) e a Relação P2/PVS (PR) foram avaliados na AO. As coletas foram realizadas com um intervalo mínimo de duas horas de abstinência ao cigarro (período tardio) e em até 10 minutos após fumar (período recente). Utilizaram-se os testes t de Student para medidas pareadas para avaliar as diferenças entre os períodos tardio e recentes de consumo (avaliação intragrupo) e o teste t de Student para a comparação entre os sexos (avaliação intergrupo). A diferença entre o período tardio e agudo foi expresso em porcentagens para a avaliação do efeito na AO e na ACM. A variação entre as velocidades intra arteriais da AO e da ACM foi estimada utilizando-se os testes ANOVA e Krukal-Walis. Consideramos significância a um nível de α ≤ 0,05 e um intervalo de confiança de 95% para todos os testes. Resultados: O grupo de estudo foi composto por 71 fumantes crônicos (34 homens e 37 mulheres). O PSV, a VDF e a VM mostraram um aumento de velocidade na AO e na ACM em ambos os vasos e sexos depois de fumar. O IR e o IP apresentaram uma diminuição em ambas as artérias depois de fumar com efeito quase exclusivo nas mulheres. O PR não se alterou em função do consumo dos cigarros, mas foi maior nas mulheres em ambos os períodos de consumo. Não houve variação do IL. Conclusões: Houve aumento das velocidades de fluxo após o consumo do cigarro em ambos os vasos e sexos, com a mesma direção de efeito, compatíveis com alterações transitórias e funcionais no leito arterial. Contudo, os achados sugerem que as mulheres apresentam maior resposta hemodinâmica ao consumo de cigarros. / Objectives: To evaluate the mean of Doppler velocities and indices of the Middle Cerebral Arteries (MCA) and Ophthalmic Arteries (OA) in chronic smokers according to the time of cigarette consumption as a function of sex. To evaluate the relations between the Middle Cerebral Artery and the Ophthalmic Artery. Methods: We used the Doppler method for assessing the Peak of Velocity Systolic (PVS), End Diastolic Velocity (EDV) and Mean Velocity (VM) in MCA and OA. MV was collected in the Internal Carotid Artery (ICA) to perform the Lindegaard Index (IL). Resistance Index (RI) and Pulsatility Index (IP) were performed in both arteries. Second Peak of Systolic Velocity (P2) and P2 / PVS (Peak Ratio _ PR) were evaluated only in the AO. The samples were collected with a minimum of two hours of cigarette withdrawal (late period) and up to 10 minutes after smoking (recent period). We used the paired t-test for the comparison between late and recent periods of cigarette consumption (intragroup assessment) and the unpaired t-test for the comparison between sexes (intergroup comparison). The difference between the late and recent period were expressed in percentages for the evaluation of the effect on the AO and the MCA were used. The variation between intra-arterial velocities in the AO and in the ACM was estimated using the ANOVA and Krukal-Walis tests. We considered significance at a level of α ≤ 0.05 and a 95% confidence interval for all tests. Results: The study group was composed by 71 chronic smokers (34 men and 37 women). The PVS, EDV and VM showed a velocity increase in OA and MCA in both sexes after smoking. RI and PI presented a decrease in both Arteries after smoking, with effect almost exclusively in women. PR was not changed after consumption of cigarettes in both sexes, but it was higher in women in both periods of consumption. There was no variation of IL. Conclusions: There was an increase in flow velocities after cigarette consumption in both arteries and sexes, presenting the same direction of effect, compatible with transient and functional alterations in the arterial bed. However, the findings suggest that women have a greater hemodynamic response to cigarette smoking. / Tese (Doutorado)

No description available.

La grossesse s’accompagne d’importantes modifications hormonales et hémodynamiques. Parmi celles-ci, le système rénine-angiotensine-aldostérone (SRAA) est activé très tôt durant la grossesse. De plus, cette augmentation du SRAA est accompagnée d’élévations du débit cardiaque et du volume plasmatique ainsi que des baisses paradoxales de la pression artérielle et de la résistance vasculaire périphérique. Ceci suggère que la grossesse induit un remaniement des réponses physiologiques normales au SRAA. Une résistance vasculaire à l’action des vasopresseurs est également observée durant la gestation. Ce phénomène serait causé par la modification de la fonction des canaux calciques et potassiques. De plus, il serait possiblement dû à la participation de la Na+/K+-ATPase, par son influence sur le potentiel membranaire des cellules des muscles lisses vasculaires (VSMC). La présence des récepteurs minéralocorticoïdes (MR) dans les VSMC laisse croire que l’aldostérone peut influencer le tonus vasculaire par des effets génomiques et non-génomiques. Compte tenu des connaissances actuelles, nous avons émis l’hypothèse que l’augmentation des taux sériques d’aldostérone durant la grossesse est responsable des changements hémodynamiques observés et que ces effets sont causés par l’activation des MR. Des rates gestantes ont été traitées avec du canrénoate de potassium (20 mg/kg•jr), un antagoniste des MR, durant la dernière semaine de gestation (sur 3). Sur des anneaux aortiques dénudés de leur endothélium, nous avons mesuré les réponses contractiles à la phényléphrine (PhE) et au KCl en présence d’un bloqueur des canaux calciques dépendants du voltage (VDCC), la nifédipine, et d’activateurs des canaux potassiques à large conductance (BKCa) et ceux dépendants de l’ATP (KATP), respectivement le NS-1619 et la cromakalim. Les réponses à la PhE et au KCl sont réduites à partir du 17e jour de gestation et le traitement au canrénoate augmente ces réponses dans tous les groupes. Les modulateurs de canaux ioniques atténuent les réponses à la PhE et au KCl. Cependant, le canrénoate modifie aussi les effets des modulateurs sur les aortes. Aucun effet ou une baisse des réponses est observable chez les rates non gestantes, tandis qu’une hausse de leur effet inhibiteur est notée chez les rates gestantes. Ces effets du canrénoate font croire que l’aldostérone participe à l’adaptation de la réactivité vasculaire durant la grossesse. Par ailleurs, le potentiel membranaire des VSMC pourrait être affecté dans la gestation. Pour vérifier cette hypothèse, nous avons évalué l’activité de la Na+/K+-ATPase, impliquée dans le contrôle du potentiel membranaire. Nos résultats démontrent que l’activité de la pompe est inhibée à partir du 19e jour de gestation. Cet effet est renversé par le canrénoate. Toutefois, comme le renversement de l’inhibition de la pompe est également présent chez les rates gestantes traitées avec du PST 2238, un antagoniste de l’ouabaïne sur la Na+/K+-ATPase, et que le canrénoate agit également comme agoniste partiel de la pompe, nous croyons que la diminution d’activité associée à la gestation est liée à une inhibition de la Na+/K+-ATPase par des stéroïdes cardiotoniques plutôt qu’à un effet des minéralocorticoïdes. L’augmention d’activité de la pompe liée au canrénoate s’accompagne d’une diminution de l’expression de la sous-unité α1, suggérant que la sous-unité α2 est responsable des variations de contractilité de l’aorte, puisque son expression n’est pas modifiée par le canrénoate. Les effets de la diminution de l’expression de la sous-unité α1, influencée par la signalisation du MR, restent à être déterminés. Néanmoins, nos résultats montrent que les modifications d’activité de la Na+/K+-ATPase influencent l’activité des canaux potassiques et que la pompe pourraient être un des éléments primordiaux dans le contrôle de la réactivité vasculaire durant la grossesse. Comme le canrénoate modifie la réactivité vasculaire, nous voulions déterminer ses impacts sur la pression artérielle. Des rates gestantes ont été traitées avec du canrénoate (20 ou 60 mg/kg•jr) et les paramètres hémodynamiques ont été évalués par radiotélémétrie. Aucune modification de la pression artérielle, du rythme cardiaque et de la pression pulsée ne sont mesurées chez les rates recevant le traitement. Toutefois, des augmentations de l’osmolalité, des taux sériques d’aldostérone et de corticostérone ainsi que de l’activité rénine plasmatique sont observées chez les animaux recevant 60 mg/kg•jr. Le canrénoate bloque donc le rétrocontrôle du SRAA. Par contre, les MR ne sont pas les principaux responsables du contrôle de la pression artérielle durant la grossesse. En conclusion, nous avons démontré que le traitement des rates au canrénoate influence la réactivité vasculaire de l’aorte durant la gestation. Cet effet est causé par la modification de l’activité de certains canaux ioniques (VDCC, BKCa et KATP). De plus, le canrénoate renverse l’inhibition de la Na+/K+-ATPase observée durant la gestation. Finalement, les actions locales de cet antagoniste des MR sur les vaisseaux sanguins ne se répercutent pas sur l’effet systémique global et aucune modification de la pression artérielle n’est observée. D’autres études seront toutefois nécessaires pour déterminer les voies de signalisation par lesquelles l’aldostérone module les réponses des canaux ioniques dans les VSMC. / Pregnancy is accompanied by important hormonal and hemodynamic modifications. Among them, the renin-angiotensin-aldosterone system (RAAS) is activated early during pregnancy. Furthermore, this increase of RAAS is accompanied by raises of cardiac output and blood volume as well as paradoxal decreases in blood pressure and peripheral vascular resistance. These suggest that pregnancy induces reorganization of the normal physiological responses to RAAS. In addition, a decreased vascular reactivity to vasoconstrictive agents is observed during pregnancy. Modifications of calcium and potassium channels function would be implicated in this phenomenon. Furthermore, an implication of the Na+/K+-ATPase is suspected, through its influence on the membrane potential of vascular smooth muscle cells (VSMC). Aldosterone, through the presence of mineralocorticoid receptors (MR) in VSMC, could control vascular tone by its genomic and non-genomic effects. With our knowledge at this time, we submit the hypothesis that the increased serum aldosterone levels of pregnancy are responsible for the hemodynamic changes associated with pregnancy and that these effects are caused by the activation of MR. Pregnant rats were treated with potassium canrenoate (20 mg/kg•d), a MR antagonist, during the last week of pregnancy (out of 3 weeks). Vascular reactivity of endothelium-denuded aortic rings was measured. Contractile responses to phenylephrine (PhE) and KCl were studied in the presence of a voltage-dependent calcium channel (VDCC) blocker, nifedipine, as well as calcium-actived (BKCa) and ATP-dependent (KATP) potassium channels activators, NS-1619 and cromakalim respectively. Vascular responses to PhE and KCl were reduced as of the 17th day of gestation. Canrenoate increased the responses to both agonists in the aortas of all the groups. Ionic channel modulators reduced the contractile responses to PhE and KCl. However, canrenoate also modified the responses to the modulators. In the aortas of non pregnant rats, no effect or a decrease of their inhibitory effect were observed while with the pregnant rats we noticed an increased effect. These results suggest that aldosterone could be implicated in the adaptation of vascular responses to pregnancy. On the other hand, VSMC membrane potential could be affected during pregnancy. To verify this hypothesis, Na+/K+-ATPase activity was evaluated since it is implicated in its control. Our results demonstrated that the pump is inhibited as of the 19th day of pregnancy. This effect was reversed by canrenoate. However, since the reversal of the inhibition of the pump was also present in pregnant rats treated with PST 2238, an ouabain antagonist on the Na+/K+-ATPase, and because canrenoate can also act as a partial agonist of the pump, we believe that the decreased activity associated with pregnancy is linked to the inhibition of the Na+/K+-ATPase by cardiotonic steroids rather than the effect of mineralocorticoids. The increased activity of the pump by canrenoate is linked with a decreased of the α1 subunit expression. This suggests that the α2 subunit of the pump would be responsible for the variations of aortic contractility since its expression is not modified by canrénoate. The effects of the diminished expression of the α1 subunit, influenced by the MR signalization, still need to be determined. Nevertheless, our results showed that modifications of Na+/K+-ATPase activity had an impact on the activity of potassium channels and that the pump could be one of the principal elements implicated in the control of vascular reactivity during pregnancy. Since canrenoate modified vascular reactivity, we wanted to determine its impact on blood pressure. Pregnant rats were treated with canrenoate (20 or 60 mg/kg•d) and hemodynamic functions were determined by radiotelemetry. No modification was observed in blood pressure, cardiac output and pulse pressure among the treated rats. However, increases in osmolality, aldosterone and corticosterone levels as well as plasma renin activity were observed in the animal receiving the 60 mg/kg•d canrénoate. Thus, canrenoate blocks the negative feedback of the RAAS. However, MR are not the principal element responsible for the control of blood pressure during pregnancy. In conclusion, we have demonstrated that canrenoate affects aortic vascular reactivity during pregnancy. This effect is perpetuated by modifying the activity of certain ionic channels (VDCC, BKCa and KATP). Furthermore, canrenoate is able to reverse the inhibition of the Na+/K+-ATPase observed during pregnancy. Finally, the local actions of this MR antagonist on blood vessels are not reflected by the global systemic effect and no modification of the blood pressure was observed. Other studies will be necessary to determine the signaling pathways by which aldosterone modulate ionic channel responses in VSMC.

La grossesse s’accompagne d’importantes modifications hormonales et hémodynamiques. Parmi celles-ci, le système rénine-angiotensine-aldostérone (SRAA) est activé très tôt durant la grossesse. De plus, cette augmentation du SRAA est accompagnée d’élévations du débit cardiaque et du volume plasmatique ainsi que des baisses paradoxales de la pression artérielle et de la résistance vasculaire périphérique. Ceci suggère que la grossesse induit un remaniement des réponses physiologiques normales au SRAA. Une résistance vasculaire à l’action des vasopresseurs est également observée durant la gestation. Ce phénomène serait causé par la modification de la fonction des canaux calciques et potassiques. De plus, il serait possiblement dû à la participation de la Na+/K+-ATPase, par son influence sur le potentiel membranaire des cellules des muscles lisses vasculaires (VSMC). La présence des récepteurs minéralocorticoïdes (MR) dans les VSMC laisse croire que l’aldostérone peut influencer le tonus vasculaire par des effets génomiques et non-génomiques. Compte tenu des connaissances actuelles, nous avons émis l’hypothèse que l’augmentation des taux sériques d’aldostérone durant la grossesse est responsable des changements hémodynamiques observés et que ces effets sont causés par l’activation des MR. Des rates gestantes ont été traitées avec du canrénoate de potassium (20 mg/kg•jr), un antagoniste des MR, durant la dernière semaine de gestation (sur 3). Sur des anneaux aortiques dénudés de leur endothélium, nous avons mesuré les réponses contractiles à la phényléphrine (PhE) et au KCl en présence d’un bloqueur des canaux calciques dépendants du voltage (VDCC), la nifédipine, et d’activateurs des canaux potassiques à large conductance (BKCa) et ceux dépendants de l’ATP (KATP), respectivement le NS-1619 et la cromakalim. Les réponses à la PhE et au KCl sont réduites à partir du 17e jour de gestation et le traitement au canrénoate augmente ces réponses dans tous les groupes. Les modulateurs de canaux ioniques atténuent les réponses à la PhE et au KCl. Cependant, le canrénoate modifie aussi les effets des modulateurs sur les aortes. Aucun effet ou une baisse des réponses est observable chez les rates non gestantes, tandis qu’une hausse de leur effet inhibiteur est notée chez les rates gestantes. Ces effets du canrénoate font croire que l’aldostérone participe à l’adaptation de la réactivité vasculaire durant la grossesse. Par ailleurs, le potentiel membranaire des VSMC pourrait être affecté dans la gestation. Pour vérifier cette hypothèse, nous avons évalué l’activité de la Na+/K+-ATPase, impliquée dans le contrôle du potentiel membranaire. Nos résultats démontrent que l’activité de la pompe est inhibée à partir du 19e jour de gestation. Cet effet est renversé par le canrénoate. Toutefois, comme le renversement de l’inhibition de la pompe est également présent chez les rates gestantes traitées avec du PST 2238, un antagoniste de l’ouabaïne sur la Na+/K+-ATPase, et que le canrénoate agit également comme agoniste partiel de la pompe, nous croyons que la diminution d’activité associée à la gestation est liée à une inhibition de la Na+/K+-ATPase par des stéroïdes cardiotoniques plutôt qu’à un effet des minéralocorticoïdes. L’augmention d’activité de la pompe liée au canrénoate s’accompagne d’une diminution de l’expression de la sous-unité α1, suggérant que la sous-unité α2 est responsable des variations de contractilité de l’aorte, puisque son expression n’est pas modifiée par le canrénoate. Les effets de la diminution de l’expression de la sous-unité α1, influencée par la signalisation du MR, restent à être déterminés. Néanmoins, nos résultats montrent que les modifications d’activité de la Na+/K+-ATPase influencent l’activité des canaux potassiques et que la pompe pourraient être un des éléments primordiaux dans le contrôle de la réactivité vasculaire durant la grossesse. Comme le canrénoate modifie la réactivité vasculaire, nous voulions déterminer ses impacts sur la pression artérielle. Des rates gestantes ont été traitées avec du canrénoate (20 ou 60 mg/kg•jr) et les paramètres hémodynamiques ont été évalués par radiotélémétrie. Aucune modification de la pression artérielle, du rythme cardiaque et de la pression pulsée ne sont mesurées chez les rates recevant le traitement. Toutefois, des augmentations de l’osmolalité, des taux sériques d’aldostérone et de corticostérone ainsi que de l’activité rénine plasmatique sont observées chez les animaux recevant 60 mg/kg•jr. Le canrénoate bloque donc le rétrocontrôle du SRAA. Par contre, les MR ne sont pas les principaux responsables du contrôle de la pression artérielle durant la grossesse. En conclusion, nous avons démontré que le traitement des rates au canrénoate influence la réactivité vasculaire de l’aorte durant la gestation. Cet effet est causé par la modification de l’activité de certains canaux ioniques (VDCC, BKCa et KATP). De plus, le canrénoate renverse l’inhibition de la Na+/K+-ATPase observée durant la gestation. Finalement, les actions locales de cet antagoniste des MR sur les vaisseaux sanguins ne se répercutent pas sur l’effet systémique global et aucune modification de la pression artérielle n’est observée. D’autres études seront toutefois nécessaires pour déterminer les voies de signalisation par lesquelles l’aldostérone module les réponses des canaux ioniques dans les VSMC. / Pregnancy is accompanied by important hormonal and hemodynamic modifications. Among them, the renin-angiotensin-aldosterone system (RAAS) is activated early during pregnancy. Furthermore, this increase of RAAS is accompanied by raises of cardiac output and blood volume as well as paradoxal decreases in blood pressure and peripheral vascular resistance. These suggest that pregnancy induces reorganization of the normal physiological responses to RAAS. In addition, a decreased vascular reactivity to vasoconstrictive agents is observed during pregnancy. Modifications of calcium and potassium channels function would be implicated in this phenomenon. Furthermore, an implication of the Na+/K+-ATPase is suspected, through its influence on the membrane potential of vascular smooth muscle cells (VSMC). Aldosterone, through the presence of mineralocorticoid receptors (MR) in VSMC, could control vascular tone by its genomic and non-genomic effects. With our knowledge at this time, we submit the hypothesis that the increased serum aldosterone levels of pregnancy are responsible for the hemodynamic changes associated with pregnancy and that these effects are caused by the activation of MR. Pregnant rats were treated with potassium canrenoate (20 mg/kg•d), a MR antagonist, during the last week of pregnancy (out of 3 weeks). Vascular reactivity of endothelium-denuded aortic rings was measured. Contractile responses to phenylephrine (PhE) and KCl were studied in the presence of a voltage-dependent calcium channel (VDCC) blocker, nifedipine, as well as calcium-actived (BKCa) and ATP-dependent (KATP) potassium channels activators, NS-1619 and cromakalim respectively. Vascular responses to PhE and KCl were reduced as of the 17th day of gestation. Canrenoate increased the responses to both agonists in the aortas of all the groups. Ionic channel modulators reduced the contractile responses to PhE and KCl. However, canrenoate also modified the responses to the modulators. In the aortas of non pregnant rats, no effect or a decrease of their inhibitory effect were observed while with the pregnant rats we noticed an increased effect. These results suggest that aldosterone could be implicated in the adaptation of vascular responses to pregnancy. On the other hand, VSMC membrane potential could be affected during pregnancy. To verify this hypothesis, Na+/K+-ATPase activity was evaluated since it is implicated in its control. Our results demonstrated that the pump is inhibited as of the 19th day of pregnancy. This effect was reversed by canrenoate. However, since the reversal of the inhibition of the pump was also present in pregnant rats treated with PST 2238, an ouabain antagonist on the Na+/K+-ATPase, and because canrenoate can also act as a partial agonist of the pump, we believe that the decreased activity associated with pregnancy is linked to the inhibition of the Na+/K+-ATPase by cardiotonic steroids rather than the effect of mineralocorticoids. The increased activity of the pump by canrenoate is linked with a decreased of the α1 subunit expression. This suggests that the α2 subunit of the pump would be responsible for the variations of aortic contractility since its expression is not modified by canrénoate. The effects of the diminished expression of the α1 subunit, influenced by the MR signalization, still need to be determined. Nevertheless, our results showed that modifications of Na+/K+-ATPase activity had an impact on the activity of potassium channels and that the pump could be one of the principal elements implicated in the control of vascular reactivity during pregnancy. Since canrenoate modified vascular reactivity, we wanted to determine its impact on blood pressure. Pregnant rats were treated with canrenoate (20 or 60 mg/kg•d) and hemodynamic functions were determined by radiotelemetry. No modification was observed in blood pressure, cardiac output and pulse pressure among the treated rats. However, increases in osmolality, aldosterone and corticosterone levels as well as plasma renin activity were observed in the animal receiving the 60 mg/kg•d canrénoate. Thus, canrenoate blocks the negative feedback of the RAAS. However, MR are not the principal element responsible for the control of blood pressure during pregnancy. In conclusion, we have demonstrated that canrenoate affects aortic vascular reactivity during pregnancy. This effect is perpetuated by modifying the activity of certain ionic channels (VDCC, BKCa and KATP). Furthermore, canrenoate is able to reverse the inhibition of the Na+/K+-ATPase observed during pregnancy. Finally, the local actions of this MR antagonist on blood vessels are not reflected by the global systemic effect and no modification of the blood pressure was observed. Other studies will be necessary to determine the signaling pathways by which aldosterone modulate ionic channel responses in VSMC.

INTRODUCTION : Les greffons de veine saphène interne (GVS) sont encore régulièrement utilisés comme conduits en chirurgie de pontage aorto-coronarien (PAC). Les dommages subis par les segments de veine saphène pendant le prélèvement et le stockage favorisent une dysfonction endothéliale qui se manifeste par une diminution de la production d'oxyde nitrique et/ou par une augmentation du niveau de stress oxydant pouvant entraîner une défaillance du greffon veineux se traduisant par une occlusion. La solution saline héparinée est la solution de préservation de référence malgré plusieurs études démontrant ses effets néfastes sur les GVS. GALA est une solution de préservation de greffons autologues vasculaires spécialement développée pour préserver l'intégrité structurale et fonctionnelle de la couche endothéliale des greffons utilisés en chirurgie de pontages aorto-coronariens. OBJECTIF : Comparer la préservation de l'intégrité des fonctions endothéliales des greffons de veine saphène après le stockage dans la solution GALA versus dans la solution saline héparinée dans le cadre d’une étude contrôlée et randomisée en étudiant la réactivité vasculaire en chambres d’organes. RÉSULTATS : Les segments de GVS d'un total de quinze patients ont été obtenus et divisés en anneaux de 3 mm de largeur. Il n'y avait pas de différences significatives dans les niveaux de contraction en réponse au chlorure de potassium, à la phényléphrine, ni dans les concentrations de phényléphrine nécessaires pour atteindre le niveau de contraction cible entre les anneaux du groupe GALA versus le groupe de saline héparinée. Les courbes dose-réponse du groupe solution GALA ont démontré une amélioration significative des relaxations dépendantes de l'endothélium par rapport au groupe solution saline héparinée. Les contractions et relaxations indépendantes de l'endothélium induites respectivement par la phényléphrine et le nitroprussiate de sodium étaient similaires dans les anneaux de GVS des deux groupes. CONCLUSION : L’utilisation intra-opératoire d'une solution développée spécifiquement pour la préservation de l’intégrité endothéliales présente un potentiel d’avantages cliniques chez les patients qui subissent une chirurgie de PAC. Les observations précédentes suggèrent que la solution GALA pourrait réduire la dysfonction endothéliale associée à la défaillance des greffons veineux et incite des évaluations à long terme plus approfondies dans le cadre d’essais cliniques. / INTRODUCTION: Saphenous vein grafts (SVGs) are still commonly used as conduits for coronary artery bypass grafting (CABG). Injury to SVGs during harvesting and storage promotes endothelial dysfunction, which is attributed to a decrease in production of nitric oxide and/or increased level of oxidative stress that can lead to vein graft failure (VGF). Heparinized saline is still the standard of care intraoperative preservation solution despite several studies demonstrating its detrimental effects on SVGs. GALA is an innovative one-time intraoperative graft storage solution developed to preserve endothelial integrity. OBJECTIVE: To investigate, in a randomized controlled study, endothelial functional integrity of saphenous vein grafts following storage in GALA vs heparinized saline using ex vivo vascular reactivity studies in organ chamber experiments. RESULTS: Segments of saphenous vein grafts from a total of fifteen patients were obtained and divided into 3 mm wide rings for evaluation. There were no significant differences in the levels of contraction in response to potassium chloride and to phenylephrine between groups, nor in the concentrations of phenylephrine needed to achieve the target level of contraction in saphenous vein graft rings. Concentration-response curves of the GALA group demonstrated a significant improvement in endothelium-dependent relaxations compared to the heparinized saline group. Endothelium-independent contractions and relaxations induced by phenylephrine and sodium nitroprusside, respectively, were not altered in saphenous vein graft rings from both groups. CONCLUSIONS: Intraoperative application of a solution developed for graft preservation demonstrated a potential benefit to protect endothelial and vascular functional integrity in saphenous vein grafts of patients undergoing CABG. These data suggest that the GALA solution may reduce endothelial dysfunction associated with vein graft failure and warrant further long-term evaluation in clinical trials.