A comparison of the short-term incorporation of erucic acid and oleic acid in the perfused guinea-pig heart.

A comparison was made of the incorporation of radioactive erucic acid and oleic acid in the isolated perfused guinea pig heart, 2, 15 and 30 min after a radioactive pulse. The complementary techniques of (a) freeze-clamping followed by lipid extraction and thin layer chromatography and (b) electron microscope autoradiography were used. The incorporation of 3H-erucic acid into esterified lipids was much slower than that of 3H-oleic acid. Less radioactive CO2 was produced by hearts perfused with 14C erucic acid then by hearts perfused with 14C oleic acid. There was no significant effect of erucic acid on the relative areas of subcellular organelles in the autoradiographs and, in particular, there was no increase in the volume of lipid droplets. However, the incorporation of radioactivity into lipid droplets was much greater with 3H-oleic acid than with 3H-erucic acid, consistent with the higher incorporation into tissue triacylglycerol. Although oxidized less than oleic acid, erucic acid was readily transported to the mitochondria. High levels of radioactivity in free fatty acid in the hearts perfused with erucic acid suggest that a low rate of activation of the fatty acid to acyl-CoA limits both oxidation and the formation of triacylglycerol. Electron microscopy of the hearts perfused with erucic acid revealed a widespread, and quantitatively demonstrable general movement of lipid droplets towards the surface of the cell. This was occasionally accompanied by a local rupturing of the sarcolemma, possibly prior to expulsion of the lipid droplet from the cell.