Adenylate cyclase activity, [3H]-dihydroalprenolol binding and fatty acid composition of rat heart membranes in essential fatty acid deficiency

Three groups of male, weanling, Sprague-Dawley rats were fed essential fatty acid (EFA) deficient (EFAD), marginally EFA-deficient (MEFAD) or control diets up to 17 weeks. Plasma membranes from heart of EFAD and MEFAD rats had lower basal and fluoride-stimulated adenylate cyclase activity as compared with the controls. The double bond index of total lipids and phospholipids, and fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene were not appreciably different in the membranes from the 3 dietary groups. The fatty acid composition of total lipids and phospholipids showed changes typical of an EFA deficiency. The feeding of control diet to the EFAD rats for 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 β -adrenergic receptors in heart of EFAD rats as compared with controls. The results suggest that, in addition to membrane fluidity, changes in the number of β -adrenergic receptors and other metabolic changes induced by EFA deficiency may be important in regulating adenylate cyclase activity in heart