Fundamentos: Ensaios prévios reunindo pacientes em series consecutivas ou randomicas sem cegamento evidenciaram beneficio da adição do cilostozol à terapia antiplaquetária em diabéticos submetidos ao implante de stents coronários farmacológicos com redução nas taxas de reestenose binária, perda tardia intra-stent e revascularização tardia da lesão alvo. Objetivos: O objetivo primário deste estudo foi verificar se a adição do cilostazol à dupla terapia antiplaquetária, proporcionaria uma redução adicional da hiperplasia intimal em diabéticos após o implante de stent farmacológico, mensurada por meio do cálculo do volume de obstrução pelo ultrassom intracoronário 9 meses após o procedimento índice. Os objetivos secundários foram aferir a angiografia quantitativa do vaso alvo e ocorrência de eventos cardíacos adversos graves (óbito, infarto do miocárdio não fatal e necessidade de nova revascularização da lesão-alvo) aos 30 dias, 9 meses e 1 ano. Casuística e métodos: Estudo prospectivo, unicêntrico, randomizado, duplo cego, reunindo 133 pacientes diabéticos, comparando pacientes que receberam cilostazol (Grupo 1, n= 65 ) versus placebo (Grupo 2, n= 68), submetidos a implante de stent coronário com liberação de zotarolimus em artéria coronária nativa com estenose maior ou igual a 50% e diâmetro de referência igual ou superior a 2,0 mm (avaliação visual), com reestudo angiográfico e análise ultrassonográfica aos 9 meses. Resultados: Os 2 grupos foram similares nas características clínicas, angiográficas e técnicas, exceto na evidencia de maior incidência de hipertensão arterial no grupo 2 (81,5% vs 94,1%, p=0,026) assim como nos diâmetros dos stents coronários utilizados, significativamente menores no grupo 1 (2,78 mm vs 2,96 mm, p<0,001). O calculo do volume de obstrução intimal por meio do ultrassom intracoronário aos 9 meses foi similar entre os grupos (33,2% vs 35,1%, p=0,069), assim como as taxas de eventos cardíacos adversos graves (12,3% vs 8,8%, p= 0,811), trombose de stent (1,5% versus 0,75%, p= 0,237), reestenose binária intra-sent (9,8% vs 6,8%, p= 0,988), perda tardia intra-stent (0,60 vs 0,64, p=0,300) e no segmento ( 0,57 vs 0,58, p= 0,387). Conclusões: A adição do cilostazol à dupla terapia antiplaquetária com ácido acetilsalicílico e clopidogrel em pacientes diabéticos submetidos à implante de stent com zotarolimus, não reduziu eventos cardíacos adversos graves ou o porcentual de hiperplasia intimal intra-stent mensurado pela análise volumétrica do ultrassom intracoronário. / Background: Previous trials with assembled patients in consecutive or random series without blindness offered evidence of the benefit adding cilostazol to the antiplatelet therapy in diabetic patients undergoing drug-eluting stents coronary implantation, with reduction in binary restenosis rates, in-stent late loss and late target lesion revascularization. Objectives: The primary objective of this study was to determine whether the addition of cilostazol to the dual antiplatelet therapy would provide an additional intimal hyperplasia reduction in diabetic patients after drug-eluting stents implantation, measured by calculating the obstruction volume through the intravascular ultrasound 9 months after the index procedure. Secondary objectives were to assess the target vessel quantitative angiography and the occurrence of serious adverse cardiac events (death, nonfatal myocardial infarction and need for a target lesion revascularization) at 30 days, 9 months and 1 year. Methods: Prospective, single center, randomized, double blinded study, gathering 133 diabetic patients, comparing who received cilostazol (Group 1, n= 65) versus placebo (Group 2, n= 68), undergoing coronary stenting, with the releasing of zotarolimus in a native coronary artery with stenosis greater than or equal to 50% and reference diameter equal to or greater than 2.0 mm (visual assessment) with the intravascularultrasound and angiographic restudy at 9 months. Results: Both groups were similar in clinical, angiographic and technical characteristics, except for a higher incidence of arterial hypertension in group 2 (81,5% vs 94,1%, p=0,026) as well as significantly lower coronary stents diameters in group 1 (2,78 mm vs 2,96 mm, p<0,001). The intimal obstruction volume calculated by the intravascularultrasound at 9 months was similar between the groups (33,2% vs 35,1%, p=0,069), as well as the rates of major adverse cardiac events (12,3% vs 8,8%, p= 0,811), stent thrombosis (1,5% versus 0,75%, p= 0,237), in-stent binary restenosis (9,8% vs 6,8%, p= 0,988), in stent late loss (0,60 vs 0,64, p=0,300) and at the segment ( 0,57 vs 0,58, p= 0,387). Conclusions: The addition of cilostazol to the dual antiplatelet therapy with acetylsalicylate acid and clopidogrel, in diabetic patients undergoing stent implantation with zotarolimus did not reduce major adverse cardiac events nor the percentage of intra-stent intimal hyperplasia measured by the intravascularultrasound volumetric analysis.

Contractility of vascular smooth muscles (VSMs) in resistance arteries determines systemic blood pressure and blood supplies to local tissues, in which ATP sensitive K+ (KATP) channels play a role. The KATP channels that couple metabolic state to cellular activity are activated by multiple hormonal vasodilators and inhibited by vasoconstrictors. To understand the molecular mechanisms for the channel regulation by vasodilators, we studied the effects of β-adrenergic receptors on Kir6.1/SUR2B in HEK cells. Stimulation of β-adrenergic receptors activated the channels, which relied on the GS-protein, adenylyl cyclase, cAMP and PKA system. Using mutational analysis, we scanned all the putative PKA sites on Kir6.1 and SUR2B subunits and identified two residues (Ser1351 and Ser1387) in SUR2B critical for channel activation. In vitro phosphorylation experiments confirmed that Ser1387 but not Ser1351 was phosphorylated in isolated SUR2B peptides. Molecular modeling and molecular dynamics simulations reveal that phosphorylation at Ser1387 causes interdomain movements in SUR2B subunit. Blockage of the movements by engineering a disulfide bond across NBD2 and TMD1 eliminated the PKA-dependent channel activation. We also studied the molecular basis for the inhibition of vascular KATP channels by PKC. In the HEK expression system, we found that the Kir6.1/SUR2B channel but not the Kir6.2/SUR2B was drastically inhibited by PKC stimulation. We constructed Kir6.1/Kir6.2 chimeras and identified two critical protein domains for the Kir6.1 channel inhibition by PKC. The distal C-terminus was the direct target of PKC where multiple phosphorylation sites were identified. These phosphorylation sites were located in a short sequence with stereotypical sequence repeats. Mutation of any decreased the effects of PKC. Joint mutation of all of them prevented the channel inhibition by PKC. The proximal N-terminus is also involved in PKC effects without phosphorylation sites, suggesting it may play a role in channel gating. Thus, this thesis provides experimental evidence for the vascular KATP channel modulation by PKA and PKC. Phosphorylation of the Kir6.1 and SUR2B subunits by PKC and PKA produce inhibition and activation of the vascular KATP channel, respectively, which appears to be one of the molecular bases contributing to vascular tone regulation by both vasoconstricting and vasodilating hormones and neurotransmitters.

Fundamentos: Ensaios prévios reunindo pacientes em series consecutivas ou randomicas sem cegamento evidenciaram beneficio da adição do cilostozol à terapia antiplaquetária em diabéticos submetidos ao implante de stents coronários farmacológicos com redução nas taxas de reestenose binária, perda tardia intra-stent e revascularização tardia da lesão alvo. Objetivos: O objetivo primário deste estudo foi verificar se a adição do cilostazol à dupla terapia antiplaquetária, proporcionaria uma redução adicional da hiperplasia intimal em diabéticos após o implante de stent farmacológico, mensurada por meio do cálculo do volume de obstrução pelo ultrassom intracoronário 9 meses após o procedimento índice. Os objetivos secundários foram aferir a angiografia quantitativa do vaso alvo e ocorrência de eventos cardíacos adversos graves (óbito, infarto do miocárdio não fatal e necessidade de nova revascularização da lesão-alvo) aos 30 dias, 9 meses e 1 ano. Casuística e métodos: Estudo prospectivo, unicêntrico, randomizado, duplo cego, reunindo 133 pacientes diabéticos, comparando pacientes que receberam cilostazol (Grupo 1, n= 65 ) versus placebo (Grupo 2, n= 68), submetidos a implante de stent coronário com liberação de zotarolimus em artéria coronária nativa com estenose maior ou igual a 50% e diâmetro de referência igual ou superior a 2,0 mm (avaliação visual), com reestudo angiográfico e análise ultrassonográfica aos 9 meses. Resultados: Os 2 grupos foram similares nas características clínicas, angiográficas e técnicas, exceto na evidencia de maior incidência de hipertensão arterial no grupo 2 (81,5% vs 94,1%, p=0,026) assim como nos diâmetros dos stents coronários utilizados, significativamente menores no grupo 1 (2,78 mm vs 2,96 mm, p<0,001). O calculo do volume de obstrução intimal por meio do ultrassom intracoronário aos 9 meses foi similar entre os grupos (33,2% vs 35,1%, p=0,069), assim como as taxas de eventos cardíacos adversos graves (12,3% vs 8,8%, p= 0,811), trombose de stent (1,5% versus 0,75%, p= 0,237), reestenose binária intra-sent (9,8% vs 6,8%, p= 0,988), perda tardia intra-stent (0,60 vs 0,64, p=0,300) e no segmento ( 0,57 vs 0,58, p= 0,387). Conclusões: A adição do cilostazol à dupla terapia antiplaquetária com ácido acetilsalicílico e clopidogrel em pacientes diabéticos submetidos à implante de stent com zotarolimus, não reduziu eventos cardíacos adversos graves ou o porcentual de hiperplasia intimal intra-stent mensurado pela análise volumétrica do ultrassom intracoronário. / Background: Previous trials with assembled patients in consecutive or random series without blindness offered evidence of the benefit adding cilostazol to the antiplatelet therapy in diabetic patients undergoing drug-eluting stents coronary implantation, with reduction in binary restenosis rates, in-stent late loss and late target lesion revascularization. Objectives: The primary objective of this study was to determine whether the addition of cilostazol to the dual antiplatelet therapy would provide an additional intimal hyperplasia reduction in diabetic patients after drug-eluting stents implantation, measured by calculating the obstruction volume through the intravascular ultrasound 9 months after the index procedure. Secondary objectives were to assess the target vessel quantitative angiography and the occurrence of serious adverse cardiac events (death, nonfatal myocardial infarction and need for a target lesion revascularization) at 30 days, 9 months and 1 year. Methods: Prospective, single center, randomized, double blinded study, gathering 133 diabetic patients, comparing who received cilostazol (Group 1, n= 65) versus placebo (Group 2, n= 68), undergoing coronary stenting, with the releasing of zotarolimus in a native coronary artery with stenosis greater than or equal to 50% and reference diameter equal to or greater than 2.0 mm (visual assessment) with the intravascularultrasound and angiographic restudy at 9 months. Results: Both groups were similar in clinical, angiographic and technical characteristics, except for a higher incidence of arterial hypertension in group 2 (81,5% vs 94,1%, p=0,026) as well as significantly lower coronary stents diameters in group 1 (2,78 mm vs 2,96 mm, p<0,001). The intimal obstruction volume calculated by the intravascularultrasound at 9 months was similar between the groups (33,2% vs 35,1%, p=0,069), as well as the rates of major adverse cardiac events (12,3% vs 8,8%, p= 0,811), stent thrombosis (1,5% versus 0,75%, p= 0,237), in-stent binary restenosis (9,8% vs 6,8%, p= 0,988), in stent late loss (0,60 vs 0,64, p=0,300) and at the segment ( 0,57 vs 0,58, p= 0,387). Conclusions: The addition of cilostazol to the dual antiplatelet therapy with acetylsalicylate acid and clopidogrel, in diabetic patients undergoing stent implantation with zotarolimus did not reduce major adverse cardiac events nor the percentage of intra-stent intimal hyperplasia measured by the intravascularultrasound volumetric analysis.

Ma, Yan. / "Ca" in the title is subscript. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 143-166). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

A utilização da cintilografia de perfusão miocárdica (CPM) estava limitada a pacientes que podiam realizar algum tipo de exercício, para ampliarmos a disponibilidade clínica da CPM, vários protocolos com estresses farmacológicos foram desenvolvidos. A adenosina fármaco amplamente utilizado, potente vasodilatador coronariano, apresenta uma importante interação com outras substâncias que anatagonizam seus efeitos, o dipiridamol, alimentos com cafeína e derivados de xantinas. O tempo de suspensão de cafeína da dieta para o uso exógeno da adenosina na realização da CPM ainda não está definido. Para testar essa hipótese avaliamos a influência da abstinência de cafeína em 24h, 12h e 1h, através de sua dosagem sérica, antes do estresse farmacológico com adenosina e sua possível repercussão nas imagens da CPM e o efeito vasodilatador no sistema cardiovascular. Definimos como objetivo primário: comparar a presença e a extensão dos defeitos reversíveis da CPM verificados em pacientes com abstinência de café por 24 horas (E1) com as imagens da randomização com 1 hora e 12 horas (E2) sem cafeína e como objetivos secundários: avaliar a presença e intensidade dos paraefeitos, comportamento da frequência cardíaca e da pressão arterial sistêmica. Foram submetidos ao estresse farmacológico com adenosina 194 pacientes para a realização da CPM, dos quais 43 pacientes preencheram os critérios para a randomização (defeitos perfusionais transitórios na CPM com adenosina). Excluímos seis pacientes (13,9%), três (6,9%) se recusaram a realizar a fase da randomização e os outros três (6,9%) nos quais não houve consenso entre os observadores em relação aos defeitos de perfusionais transitórios. A média de idade dos 37 pacientes analisados foi de 61,4 ± 8,3 anos, sendo 21 pacientes do sexo masculino (56,8%). Na avaliação das imagens da CPM, não houve diferença entre as imagens obtidas no grupo E1 comparadas as imagens de 1 (2,0 ± 1,5) hora ou 12 (12,6 ± 3,1) horas sem cafeína (E2). As médias de cafeína sérica encontradas foram de 0,14 ± 0,17 mg/l no grupo E1 do E2 de 1 hora e 0,13 ± 0,24 mg/l no grupo E1 do E2 de 12 horas, na randomização de 1 hora de 1,97± 0,83 mg/l e de 12 horas de 1,51 ± 1,46 mg/l (E1 vs. E2: p < 0,001). Em relação à presença dos paraefeitos, ocorreram em 31 pacientes (83,7%) e os mais freqüentes foram: dor precordial atípica, cansaço e dor em região cervical. Não foram observadas diferenças em relação às freqüências absolutas e relativas na ocorrência de paraefeitos entre os grupos. A intensidade dos paraefeitos foi verificada através de análise subjetiva comparando os sintomas em relação aos exames. Notou-se que em 22 pacientes (59,4%), caracterizaram o estudo randomizado como bem melhor, ou melhor, que o de 24 horas. A pressão arterial sistêmica e a freqüência cardíaca também não apresentaram diferenças entre os grupos. Conclusões: Os resultados permitem inferir que o uso da cafeína ingerida 2 horas antes da realização da CPM com adenosina foi eficaz e segura, pois apesar da modificação da resposta vasodilatadora máxima alcançada, traduzida pela melhor tolerância do exame realizado com menos tempo de ausência de cafeína na dieta, não modificou o resultado final da CPM / Myocardial perfusion imaging (MPI) in the past was only available to patients who were able to perform some type of exercise. Many protocols were developed with pharmacologic stress in order to enlarge the clinical availability of myocardial perfusion imaging (MPI). Adenosine is widely used and a potent coronary vasodilator, exhibits a significant interaction with other substances which antagonize its effects, such as dipyridamole, food products containing caffeine and xanthine derivatives. We found no clear consensus as to the time between caffeine ingestion and a cardiovascular adenosine stress test. To test this hypothesis we evaluated the influence of 24-hour, 12-hour and 1-hour caffeine abstinence, by assessing plasma caffeine levels before adenosine pharmacological stress, the possible repercussions on MPI images and vasodilatory effects on the cardiovascular system. The primary endpoint was to compare the presence and extent of reversible myocardial perfusion defects found in patients with 24-hour abstinence from coffee (E1), with images from patients randomized to 1-hour or 12-hour caffeine abstinence (E2). As secondary endpoints we evaluated the presence and intensity of paraeffects, as well as heart rate and systemic arterial blood pressure behavior. For this purpose, 194 patients underwent pharmacological stress with adenosine for MPI, 43 of whom fulfilled criteria for randomization (patients with transient perfusion defects detected on adenosine MPI). Six patients were excluded (13.9%), three patients (6.9%) who refused to undergo randomization, and other three (6.9%) in whom the observers could not reach consensus regarding transient perfusion defects. Mean age for the 37 patients analyzed was 61.4 ± 8.3 years, 21 patients male (56.8%). In the evaluation of myocardial perfusion images, no differences were detected between images obtained in the 24-hour E1 arm, and those from 1 (2.0 ± 1.5) hour or 12 (12.6 ± 3.1) hours randomization E2. Mean plasma caffeine level was 0.14 ± 0.17 mg/l in group E1 of the 1-hour arm E2, and 0.13 ± 0.24 mg/l in group (E1) of the 12-hour arm (E2), respectively, compared with 1.97± 0.83 mg/l, in the 1-hour, and 1.51 ± 1.46 mg/l, in the 12-hour (E2) randomized arms (E1 vs. E2: p < 0.001). In the 31 patients (83.7%) with presence of paraeffects, the most frequent were: atypical precordial pain, tiredness and pain on cervical area. There were no differences in the absolute and relative frequency in the occurrence of paraeffects between groups. However, with respect to the intensity of pareffects, a subjective analysis was undertaken, comparing symptoms of two exams. which resulted in 22 patients (59.4%) ranking the randomized study a lot better, or better than the 24-hour one. The systemic blood pressure and the heart rate behavior also did not reveal any significant differences between groups. Conclusions: The results may imply that the use of caffeine ingested 2 hours prior to the CPM with adenosine was effective and safe, for despite the change in maximal vasodilator response achieved, manifested by better tolerance of the examination with less time in the absence of caffeine in the diet, did not change the final result of the CPM

The KATP channels play an important role in the membrane excitability and vascular tone regulation. Previous studies indicate that the function of KATP channels is disrupted in oxidative stress seen in a variety of cardiovascular diseases, while the underlying mechanism remains unclear. Here, we demonstrate S-glutathionylation to be a modulation mechanism underlying the oxidant-mediated vascular KATP channel inhibition, the molecular basis for the channel inhibition and the alleviation of the channel inhibition by vasoactive intestinal peptide (VIP). We found that an exposure of isolated mesenteric rings to H2O2 impaired the KATP channel-mediated vascular dilation. In whole-cell recordings and inside-out patches, micromolar H2O2 or diamide caused a strong inhibition of the vascular KATP channel (Kir6.1/SUR2B) in the presence, but not in the absence, of glutathione (GSH), indicating S-glutathionylation. By co-expressions of Kir6.1 or Kir6.2 with SUR2B subunits, we found that the oxidant sensitivity of the KATP channel relied on the Kir6.1 subunit. Systematic mutational analysis revealed three cysteine residues (Cys43, Cys120 and Cys176) to be important. Among them, Cys176 was prominent, contributing to >80% oxidant sensitivity. Biochemical pull-down assay with biotinylated glutathione ethyl ester (BioGEE) showed that mutations of Cys176 impaired the oxidant-induced incorporation of GSH to the Kir6.1 subunit. Simulation modeling of Kir6.1 S-glutathionylation revealed that after incorporation to residue 176, the GSH moiety occupied a space between slide helix and two transmembrane helices. This prevented the necessary conformational change of the inner helix for channel gating, and retained the channel in its closed state. VIP is a potent vasodilator, and is shown to have protective role against oxidative stress. We found that the channel was strongly augmented by VIP and the channel activation relied on PKA phosphorylation. These results therefore indicate that 1) the vascular KATP channel is strongly inhibited in oxidative stress, 2) S-glutathionylation underlies the oxidant-mediated KATP channel inhibition, 3) Cys176 in the Kir6.1 subunit is the major site for S-glutathionylation, and 4) the Kir6.1/SUR2B channel is activated in a PKA-dependent manner by VIP that has been previously shown to alleviate oxidative stress.

Linalool is a monoterpene can be biosynthesized by some plants in the racemic form, ( })-linalool, or in the form of enantiomers, (+)-linalool or (-)-linalool. The evaluation the activity of pure isomers has become important in the discovery of new drugs with improved therapeutic potential and a lower rate of adverse effects. So, the objective of the present study was to evaluate the vasorelaxant action induced by the enantiomers, (+) and (-)-linalool in rat superior mesenteric artery, besides seeks to elucidate the mechanisms of action involved in this effect. For both, male Wistar rats (200 . 300 g) were euthanized by exsanguination under anesthesia and superior mesenteric artery was removed. Rings were obtained (1-2 mm) this artery, and were mounted in organ baths containing 10 mL of Tyrode fs solution at 37 C and gassed with carbogen. For isometric tension recordings, each ring was suspended by cotton thread fixed in a force transducer connected to an acquisition system. In rings with functional endothelium pre-contracted with 10 ÊL of phenylephrine, both enantiomers were able to induce significant concentration-dependent vasorelaxation. Such as the effect presented by the (-)-linalool (Emax = 75 } 3%, n = 6) were higher than those for the (+)-linalool (Emax = 41 } 3%, n = 4), sought to evaluate the mechanism of action involved in their action vasorelaxant. In rings without functional endothelium, the vasorelaxation induced by (-)-linalool was significantly attenuated compared to the condition where the rings with functional endothelium were pre-contracted with phenylephrine (Emax = 55 } 1.5%, n = 5). Similar results were obtained after incubation with 10-8 M of atropine, an antagonist of muscarinic receptors (Emax = 50 } 5 %; n = 5); or with 10-4 M of L-NAME, an inhibitor of NO synthesis (Emax = 57 } 5 %; n = 6); or with 30 ÊM of hydroxocobalamin, a NO scavenger (Emax = 45 } 5 %; n = 6). In rings without functional endothelium incubated with 1 mM TEA, a blocker of non-selective K+ channels, the vasorelaxation induced by (-)-linalool had not changed significantly (Emax = 70 } 4 %; n = 4). However, in endothelium-denuded rings pre-contracted with KCl 80 mM, the oil-induced relaxation was significantly higher than that obtained without functional endothelium in rings pre-contracted with phenylephrine (Emax = 92 } 2 %; n = 5). In addition, isolated concentrations of (-)-linalool significantly reduced the contractions induced by CaCl2 (10-6 . 10-2 M) or by Na3VO4 (10-5 . 3 x 10-2 M), a non-selective inhibitor of protein tyrosine phosphatases. These results suggest that the effects induced by linalool occur mainly by the action of one of its isomers, the (-)-linalool. This isomer produces an effect vasorelaxant in rat superior mesenteric artery which is in part, dependent on the endothelium which is given by the activation of muscarinic receptors and the NO release. Furthermore, the endothelium-independent vasorelaxation is due to inhibition of calcium channel voltage-sensitive and involves the sensitization of the contractile machinery in vascular smooth muscle. / Linalol e um monoterpeno que pode ser biossintetizado por algumas plantas na forma racemica, ( })-linalol, ou na forma de enantiomeros, (+)-linalol ou (-)-linalol. A avaliacao da atividade dos isomeros puros tem tornado-se importante para a descoberta de novas drogas com melhor potencial terapeutico e menor indice de efeitos colaterais. Assim, o objetivo do presente estudo foi avaliar a acao vasorelaxante induzida pelos enantiomeros, (+) e (-)-linalol em arteria mesenterica superior de rato, alem de buscar elucidar os mecanismos envolvidos neste efeito. Para tanto, ratos Wistar machos (200 . 300 g) foram sacrificados por dessangramento sob anestesia e a arteria mesenterica superior foi removida. Desta arteria foram obtidos aneis (1-2 mm) que foram mantidos em cubas para orgao isolado contendo 10 mL de solucao nutritiva de Tyrode a 37 oC e gaseificada com carbogenio. Para o registro das contracoes isometricas, cada anel foi suspenso por linha de algodao fixada a um transdutor de forca conectado a um sistema de aquisicao de dados. Em aneis com endotelio funcional pre-contraidos com 10 ÊM fenilefrina, ambos enantiomeros foram capazes de induzir vasorelaxamento significativo dependente da concentracao. Como o efeito apresentado pelo (-)-linalol (Emax = 75 } 3 %; n = 6) foi maior que aquele apresentado pelo (+)-linalol (Emax = 41 } 3 %; n = 4), buscou-se avaliar o mecanismo de acao envolvido em sua acao vasorelaxante. Em aneis sem endotelio funcional, o vasorelaxamento induzido pelo (-)-linalol foi significativamente atenuado em relacao a condicao onde os aneis com endotelio funcional foram pre-contraidos com fenilefrina (Emax = 55 } 1,5 %; n = 5). Resultados semelhantes foram obtidos apos incubacao com 10-8 M de atropina, um antagonista de receptores muscarinicos (Emax = 50 } 5 %; n = 5); ou 10-4 M de L-NAME, um inibidor da sintese de NO (Emax = 57 } 5 %; n = 6); ou 30 ÊM de hidroxocobalamina, um sequestrador de NO (Emax = 45 } 5 %; n = 6). Em aneis sem endotelio funcional pre-incubados com 1 mM de TEA, um bloqueador nao seletivo de canais para K+, o vasorelaxamento induzido pelo (-)-linalol nao foi alterado significativamente (Emax = 70 } 4 %; n = 4). Porem, em aneis sem endotelio funcional pre-contraidos com KCl 80 mM, o vasorelaxamento induzido pelo oleo foi significativamente maior que aquele obtido em aneis sem endotelio funcional pre-contraidos com fenilefrina (Emax = 92 } 2 %; n = 5). Alem disso, concentracoes isoladas de (-)-linalol foram capazes de antagonizar contracoes induzidas por CaCl2 (10-6 . 10-2 M) e Na3VO4 (10-5 . 3 x 10-2 M), um inibidor nao-seletivo de proteinas tirosina-fosfatases. Estes resultados sugerem que os efeitos induzidos pelo linalol ocorrem, principalmente, pela acao de um de seus isomeros, o (-)-linalol. Este isomero produz um efeito vasorelaxante em arteria mesenterica superior de rato que e em parte, dependente do endotelio, o qual se da pela ativacao de receptores muscarinicos e pela liberacao de NO. Alem disso, o vasorelaxamento independente do endotelio e decorrente da inibicao dos canais para calcio sensiveis a voltagem e envolve a sensibilizacao da maquinaria contratil na musculatura lisa vascular.

A utilização da cintilografia de perfusão miocárdica (CPM) estava limitada a pacientes que podiam realizar algum tipo de exercício, para ampliarmos a disponibilidade clínica da CPM, vários protocolos com estresses farmacológicos foram desenvolvidos. A adenosina fármaco amplamente utilizado, potente vasodilatador coronariano, apresenta uma importante interação com outras substâncias que anatagonizam seus efeitos, o dipiridamol, alimentos com cafeína e derivados de xantinas. O tempo de suspensão de cafeína da dieta para o uso exógeno da adenosina na realização da CPM ainda não está definido. Para testar essa hipótese avaliamos a influência da abstinência de cafeína em 24h, 12h e 1h, através de sua dosagem sérica, antes do estresse farmacológico com adenosina e sua possível repercussão nas imagens da CPM e o efeito vasodilatador no sistema cardiovascular. Definimos como objetivo primário: comparar a presença e a extensão dos defeitos reversíveis da CPM verificados em pacientes com abstinência de café por 24 horas (E1) com as imagens da randomização com 1 hora e 12 horas (E2) sem cafeína e como objetivos secundários: avaliar a presença e intensidade dos paraefeitos, comportamento da frequência cardíaca e da pressão arterial sistêmica. Foram submetidos ao estresse farmacológico com adenosina 194 pacientes para a realização da CPM, dos quais 43 pacientes preencheram os critérios para a randomização (defeitos perfusionais transitórios na CPM com adenosina). Excluímos seis pacientes (13,9%), três (6,9%) se recusaram a realizar a fase da randomização e os outros três (6,9%) nos quais não houve consenso entre os observadores em relação aos defeitos de perfusionais transitórios. A média de idade dos 37 pacientes analisados foi de 61,4 ± 8,3 anos, sendo 21 pacientes do sexo masculino (56,8%). Na avaliação das imagens da CPM, não houve diferença entre as imagens obtidas no grupo E1 comparadas as imagens de 1 (2,0 ± 1,5) hora ou 12 (12,6 ± 3,1) horas sem cafeína (E2). As médias de cafeína sérica encontradas foram de 0,14 ± 0,17 mg/l no grupo E1 do E2 de 1 hora e 0,13 ± 0,24 mg/l no grupo E1 do E2 de 12 horas, na randomização de 1 hora de 1,97± 0,83 mg/l e de 12 horas de 1,51 ± 1,46 mg/l (E1 vs. E2: p < 0,001). Em relação à presença dos paraefeitos, ocorreram em 31 pacientes (83,7%) e os mais freqüentes foram: dor precordial atípica, cansaço e dor em região cervical. Não foram observadas diferenças em relação às freqüências absolutas e relativas na ocorrência de paraefeitos entre os grupos. A intensidade dos paraefeitos foi verificada através de análise subjetiva comparando os sintomas em relação aos exames. Notou-se que em 22 pacientes (59,4%), caracterizaram o estudo randomizado como bem melhor, ou melhor, que o de 24 horas. A pressão arterial sistêmica e a freqüência cardíaca também não apresentaram diferenças entre os grupos. Conclusões: Os resultados permitem inferir que o uso da cafeína ingerida 2 horas antes da realização da CPM com adenosina foi eficaz e segura, pois apesar da modificação da resposta vasodilatadora máxima alcançada, traduzida pela melhor tolerância do exame realizado com menos tempo de ausência de cafeína na dieta, não modificou o resultado final da CPM / Myocardial perfusion imaging (MPI) in the past was only available to patients who were able to perform some type of exercise. Many protocols were developed with pharmacologic stress in order to enlarge the clinical availability of myocardial perfusion imaging (MPI). Adenosine is widely used and a potent coronary vasodilator, exhibits a significant interaction with other substances which antagonize its effects, such as dipyridamole, food products containing caffeine and xanthine derivatives. We found no clear consensus as to the time between caffeine ingestion and a cardiovascular adenosine stress test. To test this hypothesis we evaluated the influence of 24-hour, 12-hour and 1-hour caffeine abstinence, by assessing plasma caffeine levels before adenosine pharmacological stress, the possible repercussions on MPI images and vasodilatory effects on the cardiovascular system. The primary endpoint was to compare the presence and extent of reversible myocardial perfusion defects found in patients with 24-hour abstinence from coffee (E1), with images from patients randomized to 1-hour or 12-hour caffeine abstinence (E2). As secondary endpoints we evaluated the presence and intensity of paraeffects, as well as heart rate and systemic arterial blood pressure behavior. For this purpose, 194 patients underwent pharmacological stress with adenosine for MPI, 43 of whom fulfilled criteria for randomization (patients with transient perfusion defects detected on adenosine MPI). Six patients were excluded (13.9%), three patients (6.9%) who refused to undergo randomization, and other three (6.9%) in whom the observers could not reach consensus regarding transient perfusion defects. Mean age for the 37 patients analyzed was 61.4 ± 8.3 years, 21 patients male (56.8%). In the evaluation of myocardial perfusion images, no differences were detected between images obtained in the 24-hour E1 arm, and those from 1 (2.0 ± 1.5) hour or 12 (12.6 ± 3.1) hours randomization E2. Mean plasma caffeine level was 0.14 ± 0.17 mg/l in group E1 of the 1-hour arm E2, and 0.13 ± 0.24 mg/l in group (E1) of the 12-hour arm (E2), respectively, compared with 1.97± 0.83 mg/l, in the 1-hour, and 1.51 ± 1.46 mg/l, in the 12-hour (E2) randomized arms (E1 vs. E2: p < 0.001). In the 31 patients (83.7%) with presence of paraeffects, the most frequent were: atypical precordial pain, tiredness and pain on cervical area. There were no differences in the absolute and relative frequency in the occurrence of paraeffects between groups. However, with respect to the intensity of pareffects, a subjective analysis was undertaken, comparing symptoms of two exams. which resulted in 22 patients (59.4%) ranking the randomized study a lot better, or better than the 24-hour one. The systemic blood pressure and the heart rate behavior also did not reveal any significant differences between groups. Conclusions: The results may imply that the use of caffeine ingested 2 hours prior to the CPM with adenosine was effective and safe, for despite the change in maximal vasodilator response achieved, manifested by better tolerance of the examination with less time in the absence of caffeine in the diet, did not change the final result of the CPM