EFFECT OF REVERSAL OF DIET-INDUCED CHANGES IN ACYL GROUP COMPOSITION OF CARDIAC MEMBRANE-LIPIDS ON ADENYLATE-CYCLASE ACTIVITY IN RATS

The purpose of the present investigation was to determine if the diet- induced changes in cardiac adenylate cyclase activity and membrane lip ids 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 conc entrate of n-3 fatty acids (EEC) + 1% CO (group III). After 5 weeks of feeding, rats from each group were killed. Cardiac membranes were pre pared and assayed for adenylate cyclase activity. The fatty acid compo sition of membrane total phospholipids was also determined. The remain ing rats in group I were divided into four subgroups and fed the follo wing diets for the reversal study: 9% Btr + 1% CO (group la), 9% EEC f 1% CO (group Ib), 10% CO (group Ic), and 7% Btr + 2% EEC + 1% CO (gro up Id). Rats in groups II and III were maintained on their original di ets. Rats were killed 5 weeks after changing the dietary regimes, and membranes were prepared from heart and analyzed for their fatty acid c omposition of total phospholipids. Adenylate cyclase activity (basal, fluoride- and forskolin-stimulated) was also measured. The enzyme acti vity was lower in membranes of rats in group la than those in groups I I or III. Whereas the diet-induced changes in fatty acid composition w ere essentially reversed by dietary modification (groups Ib and Ic), t he changes in adenylate cyclase activity were only partially reversed.