Subacute myocardial hypoxia in the rat. An electron microscopic study of the left ventricular myocardium

Electron microscopic analysis of left ventricular myocardium from rats made hypoxic for 2h, 10 and 30 days showed focal intracellular oedema as the only alteration in acute severe hypoxia (6% oxygen). No mitochondrial lesions were seen. In chronically hypoxic hearts (9% oxygen) the mitochondrial structure also remained normal. Morphometric analysis has showed a significant increase in capillary density and in the number of mitochondria. The mean diameter of the latter seems to be smaller in hypoxic than in control hearts.