The overall aim of this Thesis was to characterise the energetic properties of the mouse papillary muscle as this preparation could become a useful model to study alterations of energetic aspects of cardiac pathologies and heart-focussed genetic changes. Measurements of resting and active metabolism of the papillary muscles were made in vitro using the myothermic technique. In the first study the mechanism underlying impaired contractility of post-ischaemic rat papillary muscle was investigated. The rat preparation is well established and was used to develop protocols and approaches that could later be used as the basis for studies with mouse papillary muscle. The muscles were exposed to simulated ischaemia for 60 min and change in energetics was studied 30 min into the reperfusion phase. The work output was reduced to 66 ± 3% of the pre-ischaemia value and the enthalpy output decreased to 71 ± 3% of pre-ischaemia value. However, there was no change in either initial, 19 ± 3%, or net mechanical efficiency, 9.0 ± 0.9%. These data, in combination with studies of Ca2+ handling, suggests that the reduced work output was caused by attachment of fewer cross-bridges in each twitch, but with no change in work generated by each cross-bridge. The following two studies involved characterisation of the energetics of the mouse papillary muscle and included measurements of resting and active metabolism. The resting metabolic rate varied with muscle size but the mean initial value was tilda 25 mW g-1 and the estimated steady value tilda 5 mW g-1 . The resting metabolic rate declined exponentially with time towards a steady value, with a time constant of 18 ± 2 min. There was no alteration in isometric force output during this time. The magnitude of resting metabolism depended inversely on muscle mass, more than doubled following a change in substrate from glucose to pyruvate and was increased 2.5-fold when the osmolarity of the bathing solution was increased by addition of 300 mM sucrose. Addition of 30 mM BDM affected neither the time course of the decline in metabolic rate nor the eventual steady value. The energy requirements associated with contractile activity were tilda7 mJ g-1 twitch-1 at a contraction frequency of 1 Hz. The enthalpy output was not affected by changing substrate from glucose to pyruvate but did decrease with an increase in temperature. The enthalpy output was partitioned into force-dependent and force-independent components using BDM to selectively inhibit cross-bridge cycling. The force-independent enthalpy output was 18.6 ± 1.9% of the initial enthalpy output. Muscle initial efficiency was &tilda32% and net efficiency tilda 17% when shortening at a realistic velocity. The enthalpy output decreased with increased contraction frequency but was independent of shortening velocity. On the basis of these values, it was calculated that the twitch energetics were consistent with ATP splitting by half the cross-bridges and the pumping of one Ca 2+ into the SR for every three cross-bridge cycles. The lack of influence of shortening velocity on energy cost supports the idea that the amount of energy to be used is determined early in a twitch and is not greatly influenced by events that occur during the contraction. The suitability of the mouse papillary muscle as a model to study ischaemia and reperfusion damage was also assessed. This preparation is excellent for studying muscle specific changes in work and enthalpy output; however, due to the long-term instability and variability amongst preparations, the suitability of this preparation in prolonged experiments remains uncertain.

Orientador: Antonio Carlos Cicogna / Banca: Paulo Jose Ferreira Tercci / Banca: Leonardo Antonio Namede Zoenoff / Resumo: A obesidade é uma doença metabólica crônica caracterizada pelo acúmulo excessivo de tecido adiposo em relação à massa magra tecidual. O número de indivíduos com sobrepeso vem crescendo mundialmente representando atualmente mais de um bilhão de pessoas, sendo que, mais de 30% desta população é obesa. No Brasil, a previsão é que 35% da população adulta brasileira se tornará obesa em 2025. Pesquisas clínicas indicam que a obesidade está associada com o aumento do risco de morbidade, mortalidade e redução na expectativa de vida, podendo acarretar diversas co-morbidades, como doenças cardiovasculares. Estudos mostram que a obesidade promove alterações hemodinâmicas, morfológicas e funcionais cardíacas, que se correlacionam com a duração e intensidade da obesidade. Modelos experimentais relacionando função cardíaca, obesidade e dieta hipercalórica por um período de 10 a 16 semanas, apresentam resultados inconsistentes. Enquanto alguns autores relataram comportamento preservado, outros observaram aumento ou diminuição do desempenho cardíaco. Em razão de poucos estudos avaliarem a relação entre função cardíaca e o trânsito intracelular de cálcio em animais obesos por dieta hipercalórica, o objetivo deste estudo foi avaliar a função cardíaca de ratos obesos submetidos a um ciclo de dietas hipercalóricas. Ratos Wistar machos, com 30 dias, foram randomizados em dois grupos: controle (C; n=28) e obeso (OB; n=25). O grupo C recebeu ração Labina (3,3 Kcal/g) e o OB um ciclo de cinco dietas hipercalóricas ( 4,5 kcal/g) durante 15 semanas. Foram analisados peso corporal final (PCF), percentual de gordura na carcaça (PG), pressão arterial sistólica final (PA), área seccional (AS) do músculo papilar, peso dos ventrículos esquerdo...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The obesity is a chronic metabolic disease characterized by the extreme accumulation of fat tissue in relation to the tissue lean mass. The number of individuals with overweight comes world-wide growing currently representing more than a billion of people, being that, more than 30% of this population are obese. In Brazil, the prevision is that 35% of the Brazilian adult population will become fat in 2025. Clinical research indicates that the obesity is associated with the increase of the risk of morbity, mortality and reduction in the life expectancy, being able to cause diverse co-morbidities, as cardiovascular diseases. Studies show that the obesity promotes hemodinamical, morphological and functional heart alterations that correlate with the duration and intensity of the obesity. Experimental models, relating cardiac function, obesity and high fat diet for a period of 10 to 16 weeks, present inconsistent results. While some authors had told about preserved behavior, others had observed increase or reduction of the cardiac performance. In reason of few studies to evaluate the relation between cardiac function and the intracellular calcium cycling in fat animals by high fat diet, the objective of this study was to evaluate the cardiac function of submitted fat rats to a cycle of high fat diet. Male Wistar rats, with 30 days, were randomly in two groups: control (C; n=28) and obese (OB; n=25). Group C received a control low-fat diet Labina (3,3 Kcal/g) and the OB a cycle from five high fat diets (4,5 kcal/g) during 15 weeks. Final corporal weight (FBW), percentage of fat of the carcass (%CF), final systolic blood pressure (SBP), cross-sectional area (CSA) of the papillary muscle, left ventricle weight (LVW), right ventricle weight (RVW) and the ratio LV/FBW and RV/FBW were... (Complete abstract click electronic access below) / Mestre

Made available in DSpace on 2014-06-11T19:23:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-02-26Bitstream added on 2014-06-13T20:30:02Z : No. of bitstreams: 1 leopoldo_as_me_botfm.pdf: 705352 bytes, checksum: c389a1e671686b344e5f7562166a86c9 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A obesidade é uma doença metabólica crônica caracterizada pelo acúmulo excessivo de tecido adiposo em relação à massa magra tecidual. O número de indivíduos com sobrepeso vem crescendo mundialmente representando atualmente mais de um bilhão de pessoas, sendo que, mais de 30% desta população é obesa. No Brasil, a previsão é que 35% da população adulta brasileira se tornará obesa em 2025. Pesquisas clínicas indicam que a obesidade está associada com o aumento do risco de morbidade, mortalidade e redução na expectativa de vida, podendo acarretar diversas co-morbidades, como doenças cardiovasculares. Estudos mostram que a obesidade promove alterações hemodinâmicas, morfológicas e funcionais cardíacas, que se correlacionam com a duração e intensidade da obesidade. Modelos experimentais relacionando função cardíaca, obesidade e dieta hipercalórica por um período de 10 a 16 semanas, apresentam resultados inconsistentes. Enquanto alguns autores relataram comportamento preservado, outros observaram aumento ou diminuição do desempenho cardíaco. Em razão de poucos estudos avaliarem a relação entre função cardíaca e o trânsito intracelular de cálcio em animais obesos por dieta hipercalórica, o objetivo deste estudo foi avaliar a função cardíaca de ratos obesos submetidos a um ciclo de dietas hipercalóricas. Ratos Wistar machos, com 30 dias, foram randomizados em dois grupos: controle (C; n=28) e obeso (OB; n=25). O grupo C recebeu ração Labina (3,3 Kcal/g) e o OB um ciclo de cinco dietas hipercalóricas ( 4,5 kcal/g) durante 15 semanas. Foram analisados peso corporal final (PCF), percentual de gordura na carcaça (PG), pressão arterial sistólica final (PA), área seccional (AS) do músculo papilar, peso dos ventrículos esquerdo... / The obesity is a chronic metabolic disease characterized by the extreme accumulation of fat tissue in relation to the tissue lean mass. The number of individuals with overweight comes world-wide growing currently representing more than a billion of people, being that, more than 30% of this population are obese. In Brazil, the prevision is that 35% of the Brazilian adult population will become fat in 2025. Clinical research indicates that the obesity is associated with the increase of the risk of morbity, mortality and reduction in the life expectancy, being able to cause diverse co-morbidities, as cardiovascular diseases. Studies show that the obesity promotes hemodinamical, morphological and functional heart alterations that correlate with the duration and intensity of the obesity. Experimental models, relating cardiac function, obesity and high fat diet for a period of 10 to 16 weeks, present inconsistent results. While some authors had told about preserved behavior, others had observed increase or reduction of the cardiac performance. In reason of few studies to evaluate the relation between cardiac function and the intracellular calcium cycling in fat animals by high fat diet, the objective of this study was to evaluate the cardiac function of submitted fat rats to a cycle of high fat diet. Male Wistar rats, with 30 days, were randomly in two groups: control (C; n=28) and obese (OB; n=25). Group C received a control low-fat diet Labina (3,3 Kcal/g) and the OB a cycle from five high fat diets (4,5 kcal/g) during 15 weeks. Final corporal weight (FBW), percentage of fat of the carcass (%CF), final systolic blood pressure (SBP), cross-sectional area (CSA) of the papillary muscle, left ventricle weight (LVW), right ventricle weight (RVW) and the ratio LV/FBW and RV/FBW were... (Complete abstract click electronic access below)

Secretin and VIP stimulate cardiac adenylyl cyclase activity and exert a positive inotropic action in several mammalian species. This study examined positive inotropic activity and cAMP levels in rat papillary muscle. Isoproterenol and secretin increased contractions by 150 ± 31% and 129 ± 27%, respectively. VIP increased contraction by 30 ± 21% only at 10 μM. Isoproterenol significantly increased cAMP levels by 82%, whereas increases by secretin (58%) and VIP (56%) were not significant. These results are consistent with reports that secretin and VIP stimulate cardiac adenylyl cyclase in the rat, but suggest that cAMP tissue levels cannot totally explain the positive inotropic responses to secretin and VIP.

Die vorliegende Untersuchung sollte die kontraktile Funktion von humanen Vorhoftrabekeln und linksventrikulären Papillarmuskeln der Ratte während Hypoxie / Reoxygenierung als Hauptkomponenten von Ischämie / Reperfusion charakterisieren. Weitere Merkmale der Ischämie wurden durch erhöhte extrazelluläre K+-Konzentration und Azidose simuliert. Einblicke in die zelluläre Ca2+-Regulation ergaben sich aus Aktionspotential-(AP)-messungen, der SR- Ca2+-ATPase-Aktivität und Kraft-Intervall- Beziehungen. Die Rolle des Energiestoffwechsels und der endogenen antioxidativen Kapazität für die kontraktile Funktion von infarktbedingt hypertrophiertem Rattenmyokard während Hypoxie / Reoxygenierung ist durch Messung der Kreatinkinase-(CK)-Aktivität, ihrer Isoenzymverteilung und der Aktivitäten von Superoxiddismutase (SOD) und Glutathionperoxidase (GSH-Px) charakterisiert worden. Der Einsatz der Radikalfänger Histidin und Butylhydroxytoluen während Hypoxie und schneller Reoxygenierung an Rattenpapillarmuskeln sollte zur Protektion gegen den toxischen Effekt unterschiedlicher reaktiver Sauerstoffspezies dienen. In den durchgeführten Experimenten zeigte sich eine geringere Empfindlichkeit des humanen Vorhofmyokards gegenüber reduzierter O2-Versorgung und Reoxygenierung als im Rattenmyokard. Die während simulierter Ischämie im humanen Myokard auftretende Azidose hat einen günstigen Effekt auf die Wiederherstellung der isometrischen Kontraktionskraft nach Reoxygenierung, was jedoch mit einer gestörten Regulation der kontraktilen Funktion verbunden ist. Hypertrophiertes Myokard in der chronischen Phase nach Infarkt zeigt eine verminderte Empfindlichkeit gegenüber Hypoxie / Reoxygenierung, was auf adaptive Veränderungen im Energiestoffwechsel (erhöhte CK-MB und CK-BB Isoenzyme mit kleinerem Km-Wert für Kreatinphosphat), in der endogenen antioxidativen Kapazität (Erhöhung der Aktivitäten von SOD und GSH-Px um 40% bzw. 50%) und in der Regulation der kontraktilen Funktion (verminderte SR Ca2+-ATPase-Aktivität und Isomyosinverschiebung von V1 nach V3) zurückgeführt werden kann. Eine bessere Erholung der kontraktilen Funktion nach Reoxygenierung kann durch schnellen pO2- Wiederanstieg erreicht werden. Der Einsatz von Pharmaka mit verschiedenen Angriffspunkten im Radikalstoffwechsel und besonders deren Kombination während Hypoxie / Reoxygenierung ermöglicht zusätzlich eine verbesserte Kardioprotektion. / This study characterizes the contractile function of human atrial trabeculae and rat left ventricular papillary muscles during hypoxia / reoxygenation as the major components of ischemia / reperfusion. Further characteristics of ischemia were simulated by increased extracellular K+ concentration and acidosis during hypoxia. Insights into the cellular Ca2+ regulation were obtained from action potential recordings, from measurements of sarcoplasmic reticulum (SR) Ca2+ transport, and from force-interval relations. We examined changes in SR calcium transport, creatine kinase (CK) system, the antioxidant enzymes glutathionperoxidase (GSH-Px) and superoxiddismutase (SOD) 6 wks. after infarction (MI) due to coronary ligation in rats. Phenotypic modifications vs. sham operation (SHAM) were related to the contractile response of hypertrophied papillary muscle to hypoxia / reoxygenation. The oxygen radical scavengers histidine and butylhydroxytoluene were applied during hypoxia and rapid reoxygenation to protect the myocardium against oxygen radical damage. Generally, human atrial trabeculae were less sensitive to reduced oxygen supply and reoxygenation when compared to rat papillary muscles. In human atrial trabeculae, isometric peak force development recovered better after simulated ischemia than after hypoxia but the regulation of contractile function was clearly disturbed. In rat papillary muscles, rapid reoxygenation caused a better recovery of contractile function after hypoxia. Application of the oxygen radical scavengers histidine, butylhydroxytoluene, and especially their combination during hypoxia / reoxygenation had additional cardioprotective effects. In MI vs. SHAM we observed under aerobic control conditions: decreses in isometric contraction and relaxation rate, a reduced Vmax-equivalent of sarcomeric shortening, a faster twitch-to- twitch decay of post-rest potentiation (PRC) which correlated closely to the decrease in SR Ca2+ uptake (-25%), a decrease in CK activity (-20%), reduced CK-MI and CK-MM, increased CK-MB and CK-BB, and enhanced activities of SOD (+40%) and GSH-Px (+50%). During hypoxia, an initial increase in peak force (PF) was followed by a slower PF decline in MI vs. SHAM. During reoxygenation, rates of contraction and relaxation recovered better in MI. In SHAM but not MI, twitch-to-twitch decay of PRC was accelerated after reoxygenation vs. aerobic control. The results suggest that adaptive changes in SR Ca2+ handling, CK isoenzymes, and antioxidant enzymes may contribute to higher resistance against reduced O2 supply and reoxygenation in hypertrophy due to MI.