Linoleate incorporation into rat liver membranes phospholipids: effect on plasma membrane ATPase activities and physical properties.

Plasma membrane phospholipids were modified by incubation in the presence of linoleyl-CoA with or without added lysolecithin (LPC) for various length of time. In the absence of LPC, a maximum of 10 nmoles linoleyl-phosphatidylcholine (PC) were synthesized and the ATPase specific activities were not affected whereas in the presence of LPC, when linoleyl-PC synthesis rose from 10 to 80 nmoles, the ATPase activities were decreased. The decrease was similar in the Na,K- or in the Mg-dependent-ATPase and reached maximally 30-40%. LPC by itself did not modify the ATPases. A concomitant decrease in DPH polarization was observed when linoleate was incorporated into phospholipids. We concluded that the decreased ATPase specific activities may be due to an increased fluidity of membranes produced by linoleyl- PC synthesis. We compare this modulation of ATPases by the membrane fluidity with the specific effect of linoleyl- PC species on adenylate cyclase.