Effects of vasopressin on the synthesis of phosphatidylethanolamines and phosphatidylcholines by isolated rat hepatocytes.

The effect of vasopressin on the biosynthesis of phosphatidylcholines and phosphatidylethanolamines was investigated in freshly isolated rat hepatocytes in suspension. Treatment of hepatocytes with vasopressin inhibits the incorporation of [Me-14C]choline into phosphatidylcholines in a dose-dependent manner. The hormone does not affect the uptake, phosphorylation or oxidation of choline. Pulse-chase studies indicate that CTP:cholinephosphate cytidylyltransferase might be subject to hormonal regulation by vasopressin. In contrast with the inhibitory effect of vasopressin on the synthesis of phosphatidylcholines, this hormone stimulates the incorporation of [1,2-14C]ethanolamine into phosphatidylethanolamines in a dose-dependent manner. Pulse and pulse-chase studies with labelled ethanolamine show that the conversion of ethanolaminephosphate to CDPethanolamine as well as the formation of phosphatidylethanolamines from CDPethanolamine and diacylglycerol are enhanced. Determination of the effect of vasopressin on the activity of the enzymes of the synthesis de novo of phosphatidylethanolamines demonstrates an increase of the activity of ethanolaminephosphotransferase, probably as a result of the increased amount of diacylglycerol in vasopressin-treated cells.