Effects of anoxia on the isolated perfused rat heart: histological, histochemical and electron-microscopic observations

A study to evaluate hematoxylin-basic fuchsin-picric acid (HBFP) and some other conventional stains in the demonstration of early anoxic lesions of the perfused rat heart has been undertaken. The extent of the anoxic injury was readily demonstrable electron-microscopically and in semithin sections by light microscopy, and at 1.5--2 hours practically all myocardial cells showed irreversible changes. The HBFP method was unreliable, giving false positive and false negative results both in the control and anoxic specimens. No clear changes were seen in the four histochemical dehydrogenase reactions applied, whereas damaged myocytes lost some of their affinity to eosin. Contraction bands were frequently seen in the anoxic hearts stained by the phosphotungstic acid-hematoxylin method. However, their presence was not in a linear accordance with the extent of the lesion. The perfusion model is not directly comparable to the myocardial infarct caused, for example, by ligating the coronary artery but, however, the present results suggest the difficulty of demonstrating the very early anoxic myocardial lesion by means other than electron microscopy.