THE ROLE OF PHOSPHOLIPASE-C IN ARGININE-VASOPRESSIN SECRETION BY RAT HYPOTHALAMI IN-VITRO

THE role of phosphatidylcholine (PC) and phosphatidylinositol (PI) spe cific phospholipase C (PLC) enzymes in the release of immunoreactive a rginine vasopressin (ir-AVP) from rat hypothalami in vitro was examine d. PC-PLC (0.05-0.1 U ml(-1)) increased ir-AVP release but PI-PLC (0.0 1-0.5U ml(-1)) did not. The response to a submaximal concentration of PC-PLC (0.075 U ml(-1)) was inhibited by the protein kinase C (PKC) in hibitor Ro 31-8220 (40 mu M) and by removal of extracellular Ca2+ but was unaffected by the nitric oxide (NO) precursor L-arginine (1 mM), t he NO synthase inhibitor N-omega-nitro-L-arginine benzyl ester (1 mM) and the phospholipase A(2) (PLA(2)) inhibitors quinacrine (100 mu M) a nd dexamethasone (1 mu M). The results suggest that PC-PLC plays an im portant role in AVP secretion. The responses to PC-PLC appear to be me diated by PKC but not by changes in NO synthase or PLA(2) activity.