P-109. U-73122, a phospholipase c antagonist inhibits effects of growth hormone on calcium in rat hepatocytes

Abstract

Bovine growth hormone (bGH) induces calcium transients in rat hepatocytes. To investigate the role of phospholipase C (PLC) in these hormone-stimulated calcium signals, the effects of U-73122 (1-[6-[[17β-3-methoxyestra-1,3,5(10)-trien-17-yl] amino] hexyl]-1 H-pyrrole-2,5-dione), an inhibitor of phospholipase C, and its inactive analog, U-73343 (1-[6-[17β-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1 H-pyrrolidine-2,5-dione), were determined. Intracellular calcium transients were measured in single rat hepatocytes microinjected with the photoprotein aequorin. Exposure to U-73122 inhibited bGH stimulated calcium transients. U-73343 elicited no effects. Also we show here that an inhibitor of dyacylglycerol kinase (R 59 022) inhibits free Ca oscillations induced by growth hormone. In conclusion, these results support the hypothesis that PLC plays a role in the calcium transients elicited by bGH and a negative feedback effect of protein kinase C on free Ca oscillations GH-induced.