Ultrastructural and histochemical changes of mitochondria in global ischemic cardiac muscle of rat.

Ultrastructural changes of mitochondria and histochemical changes of the cytochrome oxidase of mitochondria during global ischemia and in reperfused rat heart were observed under transmission electron microscope. The ultrastructural changes of mitochondria were evaluated by scoring the mitochondrial damages and by densitometry of the mitochondria as a marker of the density of the granules of the mitochondrial matrix. For demonstrating the cytochrome oxidase activity, 3,3'-diaminobenzidine (DAB) reaction was used. Histochemical modifications of the cytochrome oxidase activities were evaluated by using a scoring system of localization of the cytochrome oxidase and by densitometry of the mitochondria. In the ischemic groups, ultrastructural changes, such as a decrease of mitochondrial matrix granules and disruption of cristae, were observed from 60 min. ischemia. However, no particular ultrastructural changes were observed from 60 min. to 240 min. ischemia. In reperfusion, after 60 min. ischemia, the ultrastructures were recovered, but they were not recovered in reperfusion after 120 min. ischemia. The cytochrome oxidase activities did not change until 120 min. ischemia. However, in 240 min. ischemic groups the cytochrome oxidase was sparsely localized. Histochemical changes of cytochrome oxidase activities may lag behind the ultrastructural changes of mitochondria.