Adenylate cyclase activity, membrane fluidity and fatty acid composition of rat heart in essential fatty acid deficiency

Abstract

Three groups of male, weanling, Sprague-Dawley rats were fed diets containing 7% hydrogenated coconut oil, 6.6% hydrogenated coconut oil + 0.4% corn oil, or 7% corn oil for 8-17 weeks. These diets provided 0% (EFAD group), 0.5% (MEFAD group) or 5% (CONTROL group) of the total energy as linoleic acid, respectively. Crude plasma membranes were prepared from heart and assayed for adenylate cyclase activity. Both basal and fluoride-stimulated activity was lower in the membranes from EFAD and MEFAD rats than that of the controls. The double bond index of total lipids and phospholipids, and fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) were not appreciably different in the membranes from the three dietary groups. The fatty acid composition of total phospholipids of the membranes, however, was quite different and indicative of biochemical changes typical of an EFA deficiency. Feeding of the control diet to the EFAD or MEFAD rats for up to 6 weeks did not alleviate completely the changes in adenylate cyclase activity although the fatty acid patterns were restored to the normal levels. There was also a decrease in the number of [3H]-DHA binding sites in heart of EFAD rats as compared with their controls. The results suggest that the changes induced by EFA deficiency in the acyl group composition of membrane phospholipids and in the number of beta-adrenergic receptors may be important in regulating adenylate cyclase activity in the heart.