Effect of endothelin-1 on phospholipase D activity in osteoblast- like cells

We examined the effect of endothelin-1 (ET-1) on phosphatidylcholine-hydrolyzing phospholipase D activity in osteoblast-like MC3T3-E1 cells. ET-1 stimulated the formation of choline (EC₅₀ 10 nM) as well as that of inositol phosphates (EC₅₀ 1.2 nM). The effects of ET-1 and 12-0-tetradecanoylphorbol-13-acetate, a protein kinase C-activating phorbol ester, were additive. Staurosporine enhanced the ET-1-induced formation of choline. NaF or pertussis toxin were ineffective. The results indicate that ET-1 activates phospholipase D independent of protein kinase C in osteoblast-like cells.