Incorporation and distribution of 3H oleic acid in the isolated, perfused guinea-pig heart made hypoxic.

Improved methods of autoradiography and lipid extraction have been used to study the influence of hypoxia on the fate of radioactive fatty acids in the isolated guinea pig heart. Evidence is provided that hypoxia causes a shift of the rate-limiting step from transport into the cell to oxidation in the mitochondria. This leads to an increased radioactivity in myocardial free fatty acid and in the cytosol. Radioactivity in the mitochondria is decreased and disappears more slowly. At the same time, there is an increased radioactivity in lipid droplets and in triacylglycerol. There is no evidence of a specific location of radioactivity in the sacroplasmic reticulum.