LIPID SIGNAL-TRANSDUCTION PATHWAYS IN ANGIOTENSIN-II TYPE-1 RECEPTOR-TRANSFECTED FIBROBLASTS

A stable Chinese hamster ovary fibroblast line expressing the rat vasc ular type 1a angiotensin II (ANG II) receptor was used to study the li pid-derived signal transduction pathways elicited by type 1a ANG II re ceptor activation. ANG II caused a biphasic and dose-dependent increas e in diacylglycerol (DAG) accumulation with an initial peak at 15 s (1 81 +/- 11% of control, P < 0.02) and a second sustained peak at 5-10 m in (214 +/- 10% of control, P < 0.02). The late DAG peak was derived f rom phosphatidylcholine (PC), and the formation was blocked by ethylen e glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. ANG II also increased phosphatidic acid (PA) production nearly fourfold by 7 .5 min. In the presence of ethanol, ANG II markedly increased phosphat idylethanol (PEt) formation, indicating activation of phospholipase D (PLD). ANG II was shown to increase the mass of three separate PA spec ies, one of which apparently originated from DAG kinase action on PC-p hospholipase C (PLC)-produced DAG, providing evidence for PC-PLC activ ity. ANG II also formed a third PA species, which originated neither f rom PLD nor from DAG kinase. These results demonstrate that multiple l ipid signals propagated via collateral stimulation of PLC and PLD are generated by specific activation of the vascular type 1a ANG II recept or.