“…Triacylglycerols, phosphatidic acid or other phospholipids could also be precursors of diacylglycerol. Evidence that vasopressin or Ca2 + affect some of the reactions involved in the conversion of these lipids into diacylglycerol has been obtained (Allan & Michell, 1977;Williamson et al, 1980;Sugden & Williamson, 1981;Alemany et al, 1982;Pollard & Brindley, 1984). Comparison of the fatty acid composition of the diacylglycerols formed in the presence of vasopressin with that of triacylglycerols (Akesson, 1969), the observations that vasopressin increases the rate of fatty acid esterification (Williamson et al, 1980) and the amount of [32P]phosphatidic acid in cells prelabelled with [32P]P; (Thomas et al, 1983;Litosch et al, 1983), and the failure of glucagonwhichlhas been shown to alter hepatic triacylglycerol metab-olism (reviewed by Saggerson & Bates, 1981;Pelech et al, 1983)] to induce a transient change in diacylglycerols suggest that stimulation by vasopressin of the net conversion of triacylglycerol or phosphatidic acid into diacylglycerol is unlikely.…”