Regulation of phospholipid remodelling by thyroid hormones in the rat heart

Abstract

Membrane bound phospholipids require a distinct fatty acid composition. This is achieved through the deacylation-reacylation cycle that involves the breakdown of the parent phospholipid to a fatty acid and its lysophospholipid derivative by a phospholipase A activity. Subsequently, phospholipids are resynthesized through the action of an acyltransferase that attaches acyl-Coenzyme A thioesters to the lysophospholipid. This cycle must be carefully regulated so that the correct fatty acid composition of the phospholipids are maintained, otherwise the normal functioning of the membrane and membrane bound enzymes could be jeopardized. Thyroid hormones have profound effects on the heart. Since it is established that thyroid hormones regulate many lipid metabolizing enzymes, it is possible that the deacylation-reacylation cycle of certain phospholipids may also be regulated by thyroid hormones. The effect of a thyroid condition on phospholipid fatty acid metabolism was examined in isolated rat hearts perfused in Langendorff mode for 30 min with (1-$\rm\sp{14}C\rbrack oleic$ acid (18:1) bound to albumin in a 1:1 molar ratio. Since the most dramatic effects of thyroid condition in the perfused rat heart were directed towards phosphatidylethanolamine, the de novo biosynthetic pathways of phosphatidylethanolamine were examined in hearts perfused for 30 min with (1,2-$\rm\sp{14}C\rbrack ethanolamine$ or $\rm\lbrack\sp3H(G)\rbrack serine.$ (Abstract shortened by UMI.)