Mechanism of shear-induced prostacyclin production in endothelial cells

Human umbilical vein endothelial cells at confluence were subjected to steady shear flow. It was previously shown that flow induced a burst in prostacyclin production followed by a sustained stimulation of production several fold higher than basal levels (1). In the presence of EGTA, prostacyclin production was inhibited in the steady state phase by 74%. Preincubation of endothelial cells with quin2/AM, used here as an intracellular calcium chelator, also inhibited the production of prostacyclin (83%). Inhibition of intracellular calcium mobilization had no significant effect. Incubation of cells with nifedipine, a voltage operated channel blocker, had no effect on shear induced prostacyclin production, whereas ibuprofen decreased shear induced prostacyclin production. RHC-80267, a diacylglycerol lipase inhibitor, inhibited 66% of shear induced PGI2 production. Our results suggest that both extracellular and intracellular Ca2+ are necessary and the phospholipase C pathway may be the main source for liberating arachidonic acid in shear induced prostacyclin production.