Effect of reversal of diet-induced changes in acyl group composition of cardiac membrane lipids on adenylate cyclase activity in rats

Abstract

The purpose of the present investigation was to determine if the diet-induced changes in cardiac adenylate cyclase activity and membrane lipids can be reversed. Three groups of male weanling Sprague-Dawley rats were fed purified diets containing different fats: 9% butter (Btr) + 1% corn oil (CO) (group 1), 10% CO (group II), and 9% ethyl ester concentrate of n-3 fatty acids (EEC) + 1% CO (group III). After 5 weeks of feeding, rats from each group were killed. Cardiac membranes were prepared and assayed for adenylate cyclase activity. The fatty acid composition of membrane total phospholipids was also determined. The remaining rats in group I were divided into four subgroups and fed the following diets for the reversal study: 9% Btr + 1% CO (group Ia), 9% EEC + 1% CO (group 1b), 10% CO (group Ic), and 7% Btr + 2% EEC + 1% CO (group Id). Rats in groups II and III were maintained on their original diets. Rats were killed 5 weeks after changing the dietary regimes, and membranes were prepared from heart and analyzed for their fatty acid composition of total phospholipids. Adenylate cyclase activity (basal, fluoride- and forskolin-stimulated) was also measured. The enzyme activity was lower in membranes of rats in group Ia than those in groups II or III. Whereas the diet-induced changes in fatty acid composition were essentially reversed by dietary modification (groups Ib and Ic), the changes in adenylate cyclase activity were only partially reversed.