Hearts from the rabbits in which left coronary artery had been occluded for 10, 15, 30,45, 60, 120 and 240min were examined. The control rabbits were studied, too. The results showed that evidence of damage to myocardial cells was present at 10min after occlution,and became progressively more severe with time. The ratio of mitochondrial fraction to cell volume(Vm/Vc)increased progressively after 30min of the onset of ischemia. It increased from 30 to 45 and 45 to 60min and the figure was 28% and 60% respectively. However, it increased slightly at 60 to 120min. Area of crista inner membrane per unit mitochondrial voluine(Smi+mc/Vm)was lower slightly within 30min of ischemia. At 30 to 45 and 45 to 60min the index decreased markedly and was 15% and 17%. It remained constant within 60 and 120 min. SDH was demonstrated histochemically by NBT technique and measured histophotometrically by image analysis instrument(IAI). Results showed that SDH activity was not decreased,but increased slightly within 30min of ischemia. The activity was lower significantly at 45,60, 120 and 240min after onset of ischemia and it was the lowerest value at 240 min of ischemia.
