Adenosine triphosphate (ATP) and other nucleotides stimulate the hydrolysis of phosphatidylethanolamine in intact fibroblasts

Addition of adenosine triphosphate (ATP) to [14C]ethanolamine-prelabeled NIH 3T3 fibroblasts resulted in rapid formation of [14C]ethanolamine from the prelabeled cellular phosphatidylethanolamine (PtdEtn) pool. After 2-min exposure, 10 microM ATP had near maximal effects on PtdEtn hydrolysis. Several other nucleotides, including UTP, ITP, and the stable ATP analog adenosine 5'-O-(3-thiotriphosphate) (ATP gamma S), also had stimulatory effects on PtdEtn hydrolysis with a potency comparable to that observed with ATP. The same nucleotides which acted on PtdEtn hydrolysis also had similar stimulatory effects on the hydrolysis of phosphatidylcholine (PtdCho) in [14C]choline-labeled cells. In isolated membranes, Mg2+ greatly enhanced the stimulatory effects of ATP and ATP gamma S, but not of other nucleotides, on the hydrolysis of PtdEtn and PtdCho. Results indicate that in isolated membranes, both ATP and ATP gamma S stimulate phospholipid hydrolysis by two different mechanisms, but in intact cells only one of these mechanisms appears to be responsive to externally added nucleotides.