Histochemical study of effects of hypoxia and isoproterenol on rat myocardium

Environmental hypoxia caused myocardial degeneration in rats. The changes appeared within 2 hours and were most severe at 14 to 18 hours, decreasing thereafter, even under the continuing hypoxia. Focal necrosis, however, became apparent in areas of degeneration at 12 hours and was later replaced by scar. The findings are similar to those resulting from injection of isoproterenol. This was a cytochemical and histologic study. The changes noted relate to unmasking of intracellular phospholipid and to disturbance of hydrogen-transport systems. These important constituents of the cells may be severely compromised before any abnormality is apparent histologically. Thus, some partial explanation is offered for the discrepancy commonly apparent in anatomically normal yet malfunctioning myocardium.