Thyroxine stimulates the acylation of lysophosphatidylethanolamine in rat heart

The acylation of cardiac lysophosphatidylethanolamine (LPE) was examined in rats treated with thyroid hormone. Rats were treated for five consecutive days with thyroxine (250 microg/kg) and controls were treated with saline. On the sixth day after an overnight fast, the hearts were removed and perfused in the Langendorff mode with 0.1 mM [1-14C]oleic acid. Radioactivity incorporated into phosphatidylethanolamine (PE) was increased 1.5-fold (P < 0.025) compared to controls. Radioactivity incorporated into phosphatidylcholine was not effected. The pool size of phosphatidylethanolamine and de novo biosynthesis of this phospholipid from [3H(G)]serine or [1,2-14C]ethanolamine were unaltered by thyroxine treatment. Treatment of rats with thyroxine resulted in a 1.5-fold (P < 0.025) increase in the relative percent of oleic acid in cardiac phosphatidylethanolamine. Thyroxine treatment resulted in a 1.8-fold (P < 0.025) increase in cardiac microsomal acyl-coenzyme A:1-acyl glycerophosphorylethanolamine acyltransferase activity compared to controls whereas, phospholipase A, acyl-coenzyme A hydrolase and fatty acyl-coenzyme A synthase activities were unaltered. The results demonstrate that the reacylation of cardiac LPE is regulated by thyroid hormone.