High energy phosphate stores in the hearts of genetically dystrophic hamsters

Positive action of propionyl-L-carnitine on mechanical performance of papillary muscle from Syrian hamsters with hereditary dilated cardiomyopathy

Propionyl-L-carnitine has been shown to exert a beneficial effect on cardiac function in different experimental models of cardiomyopathy in the rat, most likely by improving cardiac metabolism and energy production. We have previously shown that, in a strain of hamsters with hereditary dilated cardiomyopathy (BIO TO.2), the mechanical activity of papillary muscle (length-tension, velocity of shortening, shortening, work and power relationship) is significantly depressed when compared to the same parameter in normal hamsters (BIO F1.B). The repeated oral treatment with propionyl-L-carnitine (60 mg/kg per os for 7 weeks) to BIO TO.2 hamsters had a significant positive inotropic effect, as indicated by an increase in developed tension up to the levels observed in papillary muscles from normal hamsters. This action is most likely associated with metabolic effects similar to those observed in rats.

Prevention of hereditary cardiomyopathy in the Syrian hamster with chronic verapamil therapy

The cardiomyopathic Syrian hamster develops genetically determined cardiac necrosis that invariably leads to premature death from congestive heart failure or arrhythmia. This hamster is a valuable model of human disease because it has many features in common with clinical dilated, congestive cardiomyopathy. Previous studies have shown that therapy for several weeks with the calcium channel blocking drug verapamil or the alpha-1 adrenoceptor blocking drug prazosin can prevent myocardial necrosis due to microvascular spasm. Other investigations have demonstrated the positive effects of verapamil in the early stages of disease. It is not clear, however, whether continued treatment can prevent the long-term expression of the cardiomyopathy or whether the disease is genetically predetermined. To address this question, hamsters were treated with oral verapamil for 7 to 8 months during the necrotizing, compensatory hypertrophy and early failure stages of disease. Analysis of myocardial pathologic and biochemical variables demonstrated that continuously treated animals were generally similar to unaffected control hamsters; discontinuous therapy led to partial protection. These findings demonstrate that virtually complete prevention of this hereditary disease is feasible; these results may have important implications for the treatment of human cardiomyopathy.

L-carnitine treatment improves cardiac performance and restores high-energy phosphate pools in cardiomyopathic Syrian hamster

Hamsters with either the dilated (BIO 53.58) or hypertrophic (BIO 14.6) form of cardiomyopathy and an inbred control strain of hamster (F1B) were treated for 6 months with high-dose L-carnitine (1 g/kg/day i.p.). After treatment, the animals were killed and their hearts perfused by the isolated working technique. Mechanical performance (as indicated by the double product of heart rate and left ventricular [LV] peak systolic pressure) of both carnitine-treated cardiomyopathic groups was increased significantly above their respective sham-treated groups. Associated with these increases in mechanical performance were significant increases in both peak-positive LV dP/dt (index of contractility) and peak negative dP/dt (index of relaxation) in both carnitine-treated myopathic groups. Serum carnitine levels were increased 10-15 times within 2 hours after injection of L-carnitine in all 3 groups. Myocardial free-carnitine levels were increased twofold in both control and dilated myopathic hearts above their respective sham-treated groups, restoring the level in the dilated hearts comparable to those of controls. Myocardial carnitine levels in the hypertrophic group were not significantly affected by treatment. Total high-energy phosphate stores, i.e., ATP plus creatine phosphate, were restored to control levels by L-carnitine treatment in both cardiomyopathic groups. Levels of the breakdown products of ATP were maintained primarily in the more readily convertible adenosine diphosphate and adenosine monophosphate forms in all three treated groups. These changes resulted in significantly higher ratios of (ATP)/(ADP + AMP + adenosine) and (creatine phosphate)/(creatine) in the treated hearts. This is the first study demonstrating that high-dose L-carnitine treatment results in improved cardiac performance and increased myocardial total high-energy phosphate stores in the Syrian hamster model with one of two distinct forms of cardiomyopathy, i.e., dilated or hypertrophic. The mechanisms for these effects of exogenous L-carnitine treatment cannot be totally explained by changes in oxidative energy metabolism.

Evaluation of the hereditary Syrian hamster cardiomyopathy by 31P nuclear magnetic resonance spectroscopy: improvement after acute verapamil therapy

The relation between metabolic and functional derangement in various cardiomyopathies has not been well characterized. This information was specifically sought in a spontaneous cardiomyopathic model. Metabolic and hemodynamic parameters were obtained in glucose-perfused beating hearts of 180-200-day-old cardiomyopathic Syrian hamsters and age-matched healthy animals. This period in the cardiomyopathic hamster lifetime is intermediary between the necrotic phase and the appearance of heart failure. We used 31P nuclear magnetic resonance spectroscopy to analyze energy metabolites and intracellular pH. Cardiomyopathic hamsters had significantly higher mole fraction values for inorganic phosphate, lower phosphocreatine mole fraction as well as lower phosphocreatine/inorganic phosphate and adenosine triphosphate/inorganic phosphate ratios. Analysis of pH indicated the presence of regions of increased acidity within the heart of myopathic hamsters. Cardiomyopathic hamsters also had significantly lower left ventricular pressure, coronary flow, and myocardial oxygen consumption. Separate groups of normal and myopathic hamsters were given verapamil for 24 hours (one injection of 4 mg/kg s.c. followed by 1.2 g/l in drinking water). Verapamil-treated myopathic hamsters had evidence of markedly improved mitochondrial function when compared with untreated animals. Left ventricular pressure and coronary flow rose to normal levels. Replacing glucose by pyruvate in the perfusate of myopathic hamsters results in a marked increase in left ventricular pressure, coronary flow, and oxygen consumption with a moderate rise in phosphocreatine. Thus, 180-200-day-old cardiomyopathic hamster heart is characterized by evidence of decreased mitochondrial function, by areas of increased acidity within the heart, and by reduced left ventricular function.(ABSTRACT TRUNCATED AT 250 WORDS)