MORPHOLOGICAL INVESTIGATIONS OF THE MYOCARDIUM OF CARDIOMYOPATHIC HAMSTERS DURING THE POSTNATAL-DEVELOPMENT AND EXPERIMENTAL HYPOXIA - A QUANTITATIVE ULTRASTRUCTURAL-STUDY

The hereditary cardiomyopathy of the Syrian hamster (strain BIO 8262) as a model of human cardiomyopathy was investigated during postnatal d evelopment using ultrastructural morphometric analysis. The aim of the study was to establish basic ultrastructural morphometric data of car diomyocytes of this model during all stages of the disease in comparis on to corresponding stages of normal development, and to compare the u ltrastructural resistance of normal and myopathic myocardium against a cute hypoxic stress. The postnatal development of this cardiomyopathy is characterized by focal myolytic lesions already in the first postna tal days, extended myofibrillic and mitochondrial damage developing af ter the 1(st) month, and features of hypertrophy. disarray of myofibri ls, thickening, and clumping of z-lines after the 4(th) month. Morphom etric parameters of myopathic cardiomyocytes differing from these of t he control are diminished volume density of myofibrils by about 10 % o f the control values in middle age, slightly increased volume density of sarcoplasmic reticulum and t-tubules in the 1(st) months, significa nt increase of them after the 3(rd) month, and significant alterations of many mitochondral parameters indicating degenerations (numeric den sity, volume density, average volume, volume density of cristae, and o f destroyed areas, and ratio of surface to volume density of mitochond rial cristae). Acute isobaric hypoxia was applied to myopathic and hea lthy hamsters of corresponding age (at day 100). Evaluation of ultrast ructural morphometric parameters of cardiomyocytes revealed that espec ially mitochondria were more affected by hypoxia in the myopathic anim als. The average mitochondrial volume was significantly more increased in the myopathic condition, the ratio of surface to volume density of cristae significantly diminished. Our ultrastructural -morphometric s tudy has shown, that morphometric parameters in general can be assigne d to the stages of cardiomyopathy, and that the ultrastructural differ ences are best expressed about the 4(th) month.