STREPTOZOTOCIN-INDUCED CARDIOMYOPATHY IN DIABETIC RATS

Microscopic quantitative cardiomyopathy was previously reported in spontaneous diabetic biobreeding (BB) rats, but the nature of the lesions remains obscure. To further study the specificity of cardiomyopathy in streptozotocin-diabetic rats and discuss the existence of diabetic heart disease, we compared 40 streptozotocin-diabetic rats (D group) with 40 normal control rats (C group) at various durations in plasma glucose, fructosamine, plasma lipid, left ventricular enzyme contents and alterations of myocardial cells and coronary artery tree under electron and light microscope respectively. In 4 weeks, D rats showed myocardial mitochondrial swelling and degeneration, whereas at 8 weeks, myocardial enzyme contents markedly decreased, and myocardial lesions were more conspicuous with disruption of myocardial cells, formation of myocardial contraction bands, dilatation of intercalated discs, deposition of glycogen granules, etc. At 11 weeks, microscopic changes were essentially similar, whereas the decrease of enzyme contents became more conspicuous. During the 11 weeks, persistent and marked hyperglycemia and elevation of fructosamine were observed, however, no abnormalities were found along the coronary artery tree in the D rats. The results indicated that cardiomyopathy is diabetes specific, and exists independently as one of the three important components of diabetic heart disease.