RESUMO
Epidemiological studies have demonstrated a relationship between the adverse influence of perinatal development and increased risk of ischemic heart disease in adults. From negative factors to which the fetus is subjected, the most important is hypoxia. The fetus may experience hypoxic stress under different conditions, including pregnancy at high altitude, pregnancy with anemia, placental insufficiency, and heart, lung, and kidney disease. One of the most common insults during the early stages of postnatal development is hypoxemia due to congenital cyanotic heart defects. Experimental studies have demonstrated a link between early hypoxia and increased risk of ischemia/reperfusion injury (I/R) in adults. Furthermore, it has been observed that late myocardial effects of chronic hypoxia, experienced in early life, may be sex-dependent. Unlike in males, perinatal hypoxia significantly increased cardiac tolerance to acute I/R injury in adult females, expressed as decreased infarct size and lower incidence of ischemic arrhythmias. It was suggested that early hypoxia may result in sex-dependent programming of specific genes in the offspring with the consequence of increased cardiac susceptibility to I/R injury in adult males. These results would have important clinical implications, since cardiac sensitivity to oxygen deprivation in adult patients may be significantly influenced by perinatal hypoxia in a sex-dependent manner.
Assuntos
Hipóxia Fetal/complicações , Isquemia Miocárdica/epidemiologia , Traumatismo por Reperfusão Miocárdica/epidemiologia , Efeitos Tardios da Exposição Pré-Natal/epidemiologia , Adulto , Feminino , Hipóxia Fetal/fisiopatologia , Coração/embriologia , Coração/fisiopatologia , Humanos , Masculino , Isquemia Miocárdica/etiologia , Isquemia Miocárdica/fisiopatologia , Traumatismo por Reperfusão Miocárdica/etiologia , Traumatismo por Reperfusão Miocárdica/fisiopatologia , Oxigênio/metabolismo , Gravidez , Efeitos Tardios da Exposição Pré-Natal/etiologia , Efeitos Tardios da Exposição Pré-Natal/fisiopatologia , Fatores de Risco , Fatores SexuaisRESUMO
Age and sex play an essential role in the cardiac tolerance to ischemia-reperfusion injury: cardiac resistance significantly decreases during postnatal maturation and the female heart is more tolerant than the male myocardium. It is widely accepted that mitochondrial dysfunction, and particularly mitochondrial permeability transition pore (MPTP) opening, plays a major role in determining the extent of cardiac ischemia-reperfusion injury. We have observed that the MPTP sensitivity to the calcium load differs in mitochondria isolated from neonatal and adult myocardium, as well as from adult male and female hearts. Neonatal and female mitochondria are more resistant both in the extent and in the rate of mitochondrial swelling induced by high calcium concentration. Our data further suggest that age- and sex-dependent specificity of the MPTP is not the result of different amounts of ATP synthase and cyclophilin D: neonatal and adult hearts, similarly as the male and female hearts, contain comparable amounts of MPTP and its regulatory protein cyclophilin D. We can speculate that the lower sensitivity of MPTP to the calcium-induced swelling may be related to the higher ischemic tolerance of both neonatal and female myocardium.
Assuntos
Coração , Mitocôndrias Cardíacas/patologia , Traumatismo por Reperfusão Miocárdica/patologia , Traumatismo por Reperfusão Miocárdica/fisiopatologia , Caracteres Sexuais , Animais , Cálcio/metabolismo , Coração/fisiopatologia , Humanos , Mitocôndrias Cardíacas/metabolismo , Proteínas de Transporte da Membrana Mitocondrial/metabolismo , Poro de Transição de Permeabilidade Mitocondrial , Traumatismo por Reperfusão Miocárdica/metabolismoRESUMO
Catecholamines are involved in the regulation of a wide variety of vital functions. The ß-adrenergic receptor (ß-AR) - adenylyl cyclase system has been identified early in embryogenesis before the heart has received adrenergic innervation. The structure of ß-receptors in the immature myocardium is similar to that in adults; there are, however, significant quantitative developmental changes in the inotropic and chronotropic responsiveness. Information on the toxic effect of the ß-AR agonists in the immature heart is surprisingly scarce, even though these agents are used in clinical practice both during pregnancy and in early postnatal development. Large doses of ß-AR agonists induce malformations of the cardiovascular system; the type of change depends upon the time at which the ß-AR agonist was administered during embryogenesis. During postnatal ontogeny, the cardiotoxicity of ß-AR agonists increased from birth to adulthood. It seems likely that despite interspecies differences, developmental changes in the cardiac sensitivity to ß-AR agonists may exist in all mammals, depending on the degree of maturation of the system involved in ß-adrenergic signaling. All the existing data draw attention to the possible harmful consequences of the clinical use of ß-AR agonists during early phases of cardiac development. Late effects of the early disturbances of the cardiac muscle cannot be excluded.
Assuntos
Agonistas Adrenérgicos beta/efeitos adversos , Catecolaminas/efeitos adversos , Coração/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Tocolíticos/efeitos adversos , Adenilil Ciclases/metabolismo , Animais , Cardiotoxicidade/etiologia , Feminino , Coração/embriologia , Humanos , Gravidez , Receptores Adrenérgicos beta/metabolismoRESUMO
In 2023, six decades have elapsed since the first experimental work on the heart muscle was published, in which a member of the Institute of Physiology of the Czech Academy of Sciences participated as an author; Professor Otakar Poupa was the founder and protagonist of this research domain. Sixty years - more than half of the century - is certainly significant enough anniversary that is worth looking back and reflecting on what was achieved during sometimes very complicated periods of life. It represents the history of an entire generation of experimental cardiologists; it is possible to learn from its successes and mistakes. The objective of this review is to succinctly illuminate the scientific trajectory of an experimental cardiological department over a 60-year span, from its inaugural publication to the present. The old truth - historia magistra vitae - is still valid. Keywords: Heart, Adaptation, Development, Hypoxia, Protection.
Assuntos
Academias e Institutos , Pesquisa Biomédica , Humanos , História do Século XX , Animais , História do Século XXI , Academias e Institutos/história , Pesquisa Biomédica/história , Pesquisa Biomédica/tendências , Coração/fisiologia , Fisiologia/história , Cardiologia/história , Cardiologia/tendências , República TchecaRESUMO
Perinatal hypoxemia may have serious long-term effects on the adult cardiovascular system and may lead to sex-dependent changes in cardiac tolerance to acute ischemia in adult life. The aim of the study was to answer the question whether gonadectomy of the male and female rats in the early phase of ontogenetic development affects the late effect of perinatal hypoxia. Pregnant Wistar rats were placed into a normobaric hypoxic chamber (12 % O(2)) 7 days before the expected date of delivery. Newborn pups were kept in the chamber with their mothers for another 5 days after birth. After hypoxic exposure all animals were kept for 3 months in room air. Some of the pups were gonadectomized right after removal from the hypoxic chamber. Ventricular arrhythmias were assessed on isolated perfused hearts. Castration did not influence arrhythmogenesis in the adult normoxic or perinatally hypoxic female hearts. Nevertheless, the number of arrhythmias was decreased in perinatally hypoxic gonadectomized males. In conclusion, we have shown that perinatal normobaric hypoxia increased cardiac tolerance to acute ischemia in adult male rats; however, it had no late effect in females. Gonadectomy did not affect arrhythmogenesis in both normoxic and hypoxic female hearts, whereas in males significantly decreased the number of arrhythmias.
Assuntos
Coração/fisiopatologia , Hipóxia/complicações , Traumatismo por Reperfusão Miocárdica/etiologia , Efeitos Tardios da Exposição Pré-Natal , Taquicardia Ventricular/etiologia , Complexos Ventriculares Prematuros/etiologia , Fatores Etários , Envelhecimento , Animais , Animais Recém-Nascidos , Modelos Animais de Doenças , Feminino , Coração/embriologia , Coração/crescimento & desenvolvimento , Hipóxia/fisiopatologia , Masculino , Traumatismo por Reperfusão Miocárdica/fisiopatologia , Traumatismo por Reperfusão Miocárdica/prevenção & controle , Orquiectomia , Ovariectomia , Gravidez , Ratos , Ratos Wistar , Fatores Sexuais , Taquicardia Ventricular/fisiopatologia , Taquicardia Ventricular/prevenção & controle , Fatores de Tempo , Complexos Ventriculares Prematuros/fisiopatologia , Complexos Ventriculares Prematuros/prevenção & controleRESUMO
Our present focus on the hypoxic immature heart is driven by clinical urgency: cyanotic congenital cardiac malformations remain the single largest cause of mortality from congenital defects and ischemic heart disease is no more the disease of the fifth and older decades but its origin as well as risk factors are present already during early ontogeny. Moreover, the number of adult patients operated for cyanotic congenital heart disease during infancy steadily increases. This group approaches the age of the rising risk of serious cardiovascular diseases, particularly ischemic heart disease. Experimental results have clearly shown that the immature heart is significantly more tolerant to oxygen deficiency than the adult myocardium. However, the mechanisms of this difference have not yet been satisfactorily clarified; they are likely the result of developmental changes in cardiac energy metabolism, including mitochondrial function. The high resistance of the newborn heart cannot be further increased by ischemic preconditioning or adaptation to chronic hypoxia; these protective mechanisms appear only with decreasing tolerance during development. Resistance of the adult myocardium to acute oxygen deprivation may be significantly influenced by perinatal hypoxia. These results suggest that the developmental approach offers new possibilities in the studies of pathogenesis, prevention and therapy of critical cardiovascular diseases.
Assuntos
Doenças Cardiovasculares/prevenção & controle , Coração/fisiopatologia , Hipóxia/fisiopatologia , Miocárdio/metabolismo , Oxigênio/metabolismo , Adaptação Fisiológica , Fatores Etários , Animais , Doenças Cardiovasculares/metabolismo , Doenças Cardiovasculares/fisiopatologia , Metabolismo Energético , Feminino , Coração/crescimento & desenvolvimento , Humanos , Hipóxia/metabolismo , Precondicionamento Isquêmico Miocárdico , Masculino , Mitocôndrias Cardíacas/metabolismo , Fatores SexuaisRESUMO
Normal increase in hemodynamic load during early postnatal life is associated with heart growth and maturation of membrane structures that is accompanied by remodeling of membrane protein and lipid components. This review describes remodeling of phospholipids (PL) in rat myocardium during normal postnatal development and during accelerated cardiac growth induced by additional workload (aorta constriction, chronic hypoxia and hyperthyroidism) imposed on the heart early after birth. Normal physiological load after birth stimulates the development of membrane structures and synthesis of PL. While hyperthyroidism accelerates these processes, pressure overload has an inhibitory effect. These changes primarily influence the maturation of mitochondrial membranes as cardiolipin is one of the most affected PL species. The most sensitive part of PL structure in their remodeling process are PL acyl chains, particularly polyunsaturated fatty acids that are the key components determining the basic physicochemical properties of the membrane bilayer and thus the function of membrane-bound proteins and membrane-derived signaling lipid molecules. It is evident that PL remodeling may significantly influence both normal and pathological postnatal development of myocardium.
Assuntos
Coração/crescimento & desenvolvimento , Hemodinâmica , Miocárdio/metabolismo , Fosfolipídeos/metabolismo , Adaptação Fisiológica , Fatores Etários , Animais , Ácidos Graxos Insaturados/metabolismo , Coração/fisiopatologia , Cardiopatias/metabolismo , Cardiopatias/fisiopatologia , Mitocôndrias Cardíacas/metabolismo , Membranas Mitocondriais/metabolismo , Conformação Molecular , Fosfolipídeos/química , RatosRESUMO
The effect of the chronic and acute antioxidant tempol (superoxide dismutase mimetic) treatment on cardiac ischemic tolerance was investigated in adult male Wistar rats. The first experimental group was given tempol (1 mM) in drinking water for three weeks, the second group received tempol (100 mg/kg, i.v.) 10 min before test ischemia, and control rats received the same volume of solvent. Anesthetized open-chest animals (pentobarbitone 60 mg/kg, i.p.) were subjected to 20-min coronary artery occlusion and 3-h reperfusion for infarct size determination. Ventricular arrhythmias were monitored during ischemia and at the beginning (5 min) of reperfusion. Acute tempol administration shifted the time profile of ischemic arrhythmias to the later phase and significantly increased the number of ischemic and reperfusion premature ventricular complexes, respectively (504 +/- 127 and 84 +/- 21) as compared with the chronically treated group (218 +/- 36 and 47 +/- 7) or controls (197 +/- 26 and 31 +/- 7). Acute tempol-treated rats exhibited a tendency to decrease infarct size (P = 0.087). The mechanism of proarrhythmic tempol action during ischemia and reperfusion remains to be elucidated.
Assuntos
Antioxidantes/efeitos adversos , Arritmias Cardíacas/fisiopatologia , Óxidos N-Cíclicos/efeitos adversos , Isquemia Miocárdica/fisiopatologia , Traumatismo por Reperfusão Miocárdica/fisiopatologia , Animais , Antioxidantes/metabolismo , Pressão Sanguínea/fisiologia , Frequência Cardíaca/fisiologia , Peróxido de Hidrogênio/metabolismo , Masculino , Infarto do Miocárdio/patologia , Ratos , Marcadores de SpinRESUMO
Statins are powerful lipid-lowering drugs, widely used in patients with hyperlipidemia and coronary artery disease. It was found, however, that statins appear to have a pleiotropic effect beyond their lipid-lowering ability. They exert anti-inflammatory, antithrombotic and antioxidant effects, increase nitric oxide production and improve endothelial dysfunction. The aim of our study was to examine the effect of chronic and acute treatment with simvastatin on the contractile function of the isolated perfused rat heart after ischemia/reperfusion injury. Contractile function was measured on isolated rat hearts, perfused according to Langendorff under constant pressure. The hearts were subjected to 20 min of global ischemia, followed by 40 min of reperfusion. To investigate the acute effect, simvastatin at a concentration of 10 micromol/l was added to the perfusion solution during reperfusion. In chronic experiments the rats were fed simvastatin at a concentration of 10 mg/kg for two weeks before the measurement of the contractile function. Acute simvastatin administration significantly increased reparation of the peak of pressure development [(+dP/dt)(max)] (52.9+/-8.2 %) after global ischemia, as compared with the control group (28.8+/-5.2 %). Similar differences were also observed in the time course of the recovery of [(+dP/dt)(max)]. Chronic simvastatin was without any protective effect. Our results reveal that the acute administration of simvastatin during reperfusion, unlike the chronic treatment, significantly reduced contractile dysfunction induced by ischemia/reperfusion injury. This supports the idea of possible cardioprotective effect of statin administration in the first-line therapy of the acute coronary syndrome.
Assuntos
Cardiotônicos/administração & dosagem , Inibidores de Hidroximetilglutaril-CoA Redutases/administração & dosagem , Contração Miocárdica/efeitos dos fármacos , Traumatismo por Reperfusão Miocárdica/prevenção & controle , Sinvastatina/administração & dosagem , Função Ventricular Esquerda/efeitos dos fármacos , Animais , Circulação Coronária/efeitos dos fármacos , Modelos Animais de Doenças , Esquema de Medicação , Masculino , Traumatismo por Reperfusão Miocárdica/fisiopatologia , Perfusão , Ratos , Ratos Wistar , Pressão Ventricular/efeitos dos fármacosRESUMO
This review deals with the capability of the heart to adapt to chronic hypoxia in animals exposed to either natural or simulated high altitude. From the broad spectrum of related issues, we focused on the development and reversibility of both beneficial and adverse adaptive myocardial changes. Particular attention was paid to cardioprotective effects of adaptation to chronic high-altitude hypoxia and their molecular mechanisms. Moreover, interspecies and age differences in the cardiac sensitivity to hypoxia-induced effects in various experimental models were emphasized.
Assuntos
Aclimatação/fisiologia , Altitude , Hipóxia/metabolismo , Miocárdio/metabolismo , Oxigênio/sangue , Fatores Etários , Animais , Pressão Atmosférica , Doença Crônica , Hipóxia/complicações , Isquemia/etiologia , Isquemia/metabolismo , Traumatismo por Reperfusão Miocárdica/etiologia , Traumatismo por Reperfusão Miocárdica/metabolismoRESUMO
Clinical and experimental studies have repeatedly indicated that overloaded hearts have a higher vulnerability to ischemia/reperfusion injury. The aim of the present study was to answer the question whether the degree of tolerance to oxygen deprivation in hearts of spontaneously hypertensive rats (SHR) may be sex-dependent. For this purpose, adult SHR and their normotensive control Wistar Kyoto (WKY) rats were used. The isolated hearts were perfused according to Langendorff at constant pressure (proportionally adjusted to the blood pressure in vivo). Recovery of contractile parameters (left ventricular systolic, diastolic and developed pressure as well as the peak rate of developed pressure) was measured during reperfusion after 20 min of global no-flow ischemia in 5 min intervals. Mean arterial blood pressure was measured by direct puncture of carotid artery under light ether anesthesia in a separate group of animals. The degree of hypertension was comparable in both sexes of SHR. The recovery of contractile functions in SHR males and females was significantly lower than in WKY rats during the whole investigated period. There was no sex difference in the recovery of WKY animals; on the other hand, the recovery was significantly better in SHR females than in SHR males. It may be concluded that the hearts of female SHR are more resistant to ischemia/reperfusion injury as compared with male SHR. This fact could have important clinical implications for the treatment of cardiovascular disease in women.
Assuntos
Hipertensão/fisiopatologia , Traumatismo por Reperfusão Miocárdica/fisiopatologia , Animais , Pressão Sanguínea , Feminino , Hipertensão/complicações , Masculino , Contração Miocárdica/fisiologia , Traumatismo por Reperfusão Miocárdica/complicações , Ratos , Ratos Endogâmicos SHR , Ratos Endogâmicos WKYRESUMO
Cytochrome-c oxidase (COX) activity of the rat heart was two- to sevenfold activated when the membrane integrity was disrupted by hypotonic swelling, freezing-thawing, or a detergent, indicating that a large portion of COX capacity in intact mitochondria is not active. The effect of detergent was tested in heart mitochondria isolated from 1-, 5-, 15-, 29-, and 60-d-old rats; activation by detergent was up to 20-fold in 1-d-old animals, whereas in mitochondria from 60-d-old rats it was only 7-fold. Our data indicate that the rat heart exhibits significant developmental changes dependent on downregulation of COX activity in the neonatal period.
Assuntos
Envelhecimento/metabolismo , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Regulação Enzimológica da Expressão Gênica/fisiologia , Mitocôndrias Cardíacas/enzimologia , Miocárdio/enzimologia , Envelhecimento/efeitos dos fármacos , Animais , Animais Recém-Nascidos , Células Cultivadas , Detergentes/administração & dosagem , Regulação para Baixo/efeitos dos fármacos , Ativação Enzimática/efeitos dos fármacos , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Coração/efeitos dos fármacos , Masculino , Mitocôndrias Cardíacas/efeitos dos fármacos , Ratos , Ratos WistarRESUMO
We examined the effect of MCC-134, a novel inhibitor of mitochondrial ATP-sensitive K(+) (mitoK(ATP)) channels and activator of sarcolemmal ATP-sensitive K(+) (sarcK(ATP)) channels, on cardioprotection conferred by adaptation to chronic hypoxia. Adult male Wistar rats were exposed to intermittent hypobaric hypoxia (7000 m, 8 h/day, 5-6 weeks) and susceptibility of their hearts to ventricular arrhythmias and myocardial infarction was evaluated in anesthetized open-chest animals subjected to 20-min coronary artery occlusion and 3-h reperfusion on the day after the last hypoxic exposure. MCC-134 was administered intravenously 10 min before ischemia and 5 min before reperfusion in a total dose of 0.3 mg/kg or 3 mg/kg divided into two equal boluses. The infarct size (tetrazolium staining) was reduced from 59.2+/-4.4 % of the area at risk in normoxic controls to 43.2+/-3.3 % in the chronically hypoxic group. Chronic hypoxia decreased the reperfusion arrhythmia score from 2.4+/-0.5 in normoxic animals to 0.7+/-0.5. Both doses of MCC-134 completely abolished the antiarrhythmic protection (score 2.4+/-0.7 and 2.5+/-0.5, respectively) but only the high dose blocked the infarct size-limiting effect of chronic hypoxia (54.2+/-3.7 %). MCC-134 had no effect in the normoxic group. These results support the view that the opening of mitoKATP channels but not sarcKATP channels plays a crucial role in the mechanism by which chronic hypoxia improves cardiac tolerance to ischemia/reperfusion injury.
Assuntos
Transportadores de Cassetes de Ligação de ATP/agonistas , Adaptação Fisiológica/efeitos dos fármacos , Adaptação Fisiológica/fisiologia , Bloqueadores dos Canais de Cálcio/farmacologia , Hipóxia/fisiopatologia , Imidazóis/farmacologia , Mitocôndrias Cardíacas/efeitos dos fármacos , Traumatismo por Reperfusão Miocárdica/prevenção & controle , Canais de Potássio Corretores do Fluxo de Internalização/agonistas , Sarcolema/metabolismo , Tioamidas/farmacologia , Animais , Pressão Sanguínea/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Técnicas In Vitro , Canais KATP , Masculino , Infarto do Miocárdio/patologia , Infarto do Miocárdio/prevenção & controle , Traumatismo por Reperfusão Miocárdica/patologia , Ratos , Ratos Wistar , Sarcolema/efeitos dos fármacosRESUMO
Adaptation to intermittent high altitude hypoxia (IHAH) increases tolerance of the isolated neonatal rat heart to ischemia and potentiates protection induced by ischemic preconditioning. In addition to the protective effect, IHAH significantly reduces growth of the animals. The aim of the present study was, therefore, to find out whether low body weight per se might influence cardiac sensitivity to oxygen deprivation. Low body weight was induced either by IHAH (barochamber, 8 h/day, 5000 m) from postnatal day 1 to 10 (HLBW), or by a higher number of sucklings per mother (14 instead of 8), again from postnatal day 1 to 10 (NLBW). Control animals (8 littermates per mother) were kept under normoxic conditions (Controls). The recovery of developed force following 40 min of global ischemia was measured in isolated hearts from 10-day-old rats by perfusing them in the Langendorff mode with Krebs-Henseleit solution at constant pressure, temperature and rate. Ischemic preconditioning was induced by three 3-min periods of global ischemia, each separated by 5-min periods of reperfusion. Low body weight in HLBW and NLBW groups was accompanied by increased hematocrit, and decrease in absolute heart weight (both wet and dry) and developed force. On the other hand, higher hydration, increased cardiac tolerance to ischemia and potentiation of protection by ischemic preconditioning were observed in HLBW rats only. This experimental group also exhibited the highest relative heart weight. It may be concluded that low body weight alone does not influence cardiac tolerance to ischemia in neonatal rats.
Assuntos
Animais Recém-Nascidos/fisiologia , Peso ao Nascer/fisiologia , Coração/fisiopatologia , Isquemia Miocárdica/fisiopatologia , Doença da Altitude/fisiopatologia , Animais , Peso Corporal/fisiologia , Retardo do Crescimento Fetal/fisiopatologia , Testes de Função Cardíaca , Hematócrito , Hipóxia/fisiopatologia , Tamanho da Ninhada de Vivíparos/fisiologia , Contração Miocárdica/fisiologia , Tamanho do Órgão/fisiologia , Ratos , Ratos WistarRESUMO
The incorporation of 14C-proline into collagenous and non-collagenous proteins of the right and left ventricular myocardium was investigated in rats exposed to intermittent high altitude hypoxia. Experimental results have shown that even in control animals significant differences exist in the concentration and synthesis of individual protein fractions between the right and left ventricular myocardium. Long-term exposure to intermittent high altitude hypoxia induced a significantly increased concentration of collagenous and non-collagenous proteins in both ventricles. The incorporation of 14C-proline was not affected at this period (ie period of stabilised hypertrophy) in either of the fractions studied.
Assuntos
Doença da Altitude/metabolismo , Hipóxia/metabolismo , Miocárdio/metabolismo , Biossíntese de Proteínas , Animais , Cardiomegalia/metabolismo , Colágeno/biossíntese , Ventrículos do Coração/metabolismo , Masculino , Prolina/metabolismo , Proteínas/isolamento & purificação , RatosRESUMO
OBJECTIVE: The aim was to determine left and right ventricular functional reserves and collagen concentration during the development of cardiac hypertrophy and after its regression. METHODS: Two experimental models of cardiac hypertrophy (chronic thyroxine or isoprenaline treatment of adult rats) were compared 24 h and five weeks after the agent was last given. Pressure changes in the left (right) ventricle before and after acute aortic (pulmonary artery) ligation were recorded in open chest anaesthetised animals. The difference in dP/dtmax after and before ligation was regarded as the functional reserve. The total collagen concentration was determined in both ventricles separately by means of hydroxyproline. RESULTS: Left and right ventricular weight increased by 20% and 30% respectively in the two models employed. In the thyroxine treated group, the functional reserve of the left ventricle rose very noticeably, whereas in the isoprenaline treated group it decreased. The right ventricular functional reserve did not differ from that in the controls in either of the two groups. The collagen concentration rose in the left ventricle in the isoprenaline group only. Five weeks after the last administration of the agent, cardiac mass and ventricular function did not differ from the control values in either of the models studied; the only exception was the incomplete regression of left ventricular hypertrophy and persistent structural and functional impairment of the left ventricle in the isoprenaline treated group. CONCLUSIONS: Our results indicate that hearts undergoing a comparable degree of experimental hypertrophy may have different functional and structural properties; significant differences were found between the right and left ventricular response. Regression of hypertrophy together with a reversal of ventricular function usually occurs unless the myocardium has received severe structural damage.
Assuntos
Cardiomegalia/fisiopatologia , Função Ventricular/fisiologia , Animais , Cardiomegalia/metabolismo , Colágeno/análise , Modelos Animais de Doenças , Ventrículos do Coração/química , Isoproterenol , Masculino , Ratos , Ratos Wistar , Tiroxina , Função Ventricular Esquerda/fisiologia , Função Ventricular Direita/fisiologiaRESUMO
Counting of isolated cardiomyocytes has demonstrated that their number was 16.8 +/- 0.6 10(6) in both ventricles of weanling rats (28 days after birth), growing in litters of four (fast-growing). In rats growing in litters of 16 (slow-growing), the myocyte number was 11.8 +/- 0.8 10(6). In the control group (8 sucklings per litter), there were 14.2 +/- 10(6) cardiomyocytes. The fast-growing rats had more octoploid cells than slow-growing ones. Considering ploidy and cell number, the total number of myocyte genomes in fast-growing animals was 45% higher than in slow-growing ones. The total content of contractile proteins in fast-growing weanling animals was higher by 28% while sarcoplasmic proteins were 8% higher. This lack of correspondence between the number of myocyte genomes and muscle protein content was even more pronounced at the age of 110 days. The results are compared with the cytophotometric data concerning the lack of correspondence between the total protein content in a myocyte and its DNA amount and chromosome number, i.e., total dosage of the myocyte genes.
Assuntos
Proteínas Musculares/análise , Miocárdio/química , Retículo Sarcoplasmático/química , Animais , Contagem de Células , Proteínas Contráteis/análise , Proteínas Contráteis/genética , DNA/análise , Proteínas Musculares/genética , Ploidias , Ratos , Ratos Endogâmicos/crescimento & desenvolvimentoRESUMO
Exercise stimulates increases in heart rate (HR), stroke volume (SV) and cardiac output (CO). These adaptive mechanisms are strongly dependent on the type of exercise. Both rowing and cycling are widely used for physical training worldwide; however, evidence regarding the differences in major hemodynamic parameters during rowing and cycling remains insufficient. Ten healthy male volunteers were randomly assigned to perform either a rowing or cycling exercise. After 20 min rest, the group who had rowed first performed the cycling exercise and vice versa. Exercise was performed at a power-to-weight ratio of 2 W/kg for 2 min. HR, SV, CO and blood pressure (BP) were measured noninvasively using pulse-wave analysis at baseline and immediately after each exercise. HR, SV and CO were significantly higher after exercise than at rest. Whereas HR was comparable between rowing and cycling, SV and CO were significantly higher after rowing than after cycling. BP was comparable among all three measurements. Rowing increased SV and CO to a greater extent than cycling, whereas HR and BP were not influenced by the type of exercise. Our data suggest that rowing leads to more extensive stimulation of cardiac contractility and/or decreases in peripheral vascular resistance compared with cycling.
Assuntos
Ciclismo/fisiologia , Débito Cardíaco/fisiologia , Exercício Físico/fisiologia , Volume Sistólico/fisiologia , Pressão Sanguínea/fisiologia , Humanos , Masculino , Consumo de Oxigênio/fisiologia , Educação Física e Treinamento , Resistência Vascular/fisiologia , Adulto JovemRESUMO
It has been suggested that increase in acute nitric oxide (NO) or cyclic guanosine monophosphate production may be involved in cardioprotection induced by chronic hypoxia (CH). We studied the effect of NO donor molsidomine and phosphodiesterase type 5 inhibitor sildenafil on myocardial ischemia/reperfusion (I/R) injury in rats adapted to CH. Male Wistar rats were exposed to continuous hypoxia in a normobaric chamber (10 % O(2), 4 weeks). Rats received either saline, molsidomine (10 mg/kg body weight, i.v.) or sildenafil (0.7 mg/kg body weight, i.v.) 30 min before ischemia. Control rats were kept under normoxia and treated in a corresponding manner. Adaptation to CH increased the myocardial ischemic tolerance. Acute treatment with either molsidomine or sildenafil significantly reduced infarct size in normoxic rats and further enhanced cardioprotection induced by CH. However, the cardioprotective effect of CH on I/R injury was not additive to the cardioprotection provided by the drugs.
Assuntos
GMP Cíclico/fisiologia , Hipóxia/metabolismo , Isquemia Miocárdica/metabolismo , Óxido Nítrico/fisiologia , Transdução de Sinais/fisiologia , Animais , Doença Crônica , Masculino , Ratos , Ratos WistarRESUMO
Although there are abundant data on ischemic postconditioning (IPoC) in the adult myocardium, this phenomenon has not yet been investigated in neonatal hearts. To examine possible protective effects of IPoC, rat hearts isolated on days 1, 4, 7 and 10 of postnatal life were perfused according to Langendorff. Developed force (DF) of contraction was measured by an isometric force transducer. Hearts were exposed to 40 or 60 min of global ischemia followed by reperfusion up to the maximum recovery of DF. IPoC was induced by three cycles of 10, 30 or 60 s periods of global ischemia/reperfusion. To further determine the extent of ischemic injury, lactate dehydrogenase (LDH) release was measured in the coronary effluent. Tolerance to ischemia did not change from day 1 to day 4 but decreased to days 7 and 10. None of the postconditioning protocols tested led to significant protection on the day 10. Prolonging the period of sustained ischemia to 60 min on day 10 did not lead to better protection. The 3x30 s protocol was then evaluated on days 1, 4 and 7 without any significant effects. There were no significant differences in LDH release between postconditioned and control groups. It can be concluded that neonatal hearts cannot be protected by ischemic postconditioning during first 10 days of postnatal life.