Heterogeneity of cell response to early anoxia and reoxygenation in rat heart

Heterogeneous cell injury and increased tissue calcium levels were observed in the isolated rat hearts perfused with anoxic medium for 5, 10, 15, 20, 25 and 30 min. These changes were intensified after reoxygenation of the anoxic hearts. The cell injury was quantitated using a score of 0, 1, 2 or 3 (0 being normal and 3 being severe injury). All four classes of cells were present even after 5 min of anoxia. The injury and calcium content increased with increase in duration of anoxia. Reduction in the percentage of injured cells was observed on reoxygenation of hearts perfused with anoxic medium for 5 to 20 min. However, reoxygenation of hearts initially perfused with anoxic medium for 25 to 30 min resulted in a higher percentage of injured myocytes. Beneficial effects of reoxygenation were observed in the anoxic hearts when the percentage of cells with an injury score of 1 and glycogen deposit were high, coupled with low calcium levels.