EFFECT OF ENDOTHELIN-1 ON PHOSPHOLIPASE-D ACTIVITY IN OSTEOBLAST-LIKECELLS

We examined the effect of endothelin-1 (ET-1) on phosphatidylcholine-h ydrolyzing phospholipase D activity in osteoblast-like MC3T3-E1 cells. ET-1 stimulated the formation of choline (EC(50) 10 nM) as well as th at of inositol phosphates (EC(50) 1.2 nM). The effects of ET-1 and 12- O-tetradecanoylphorbol-13-acetate, a protein kinase C-activating phorb ol ester, were additive. Staurosporine enhanced the ET-1-induced forma tion of choline. NaF or pertussis toxin were ineffective. The results indicate that ET-1 activates phospholipase D independent of protein ki nase C in osteoblast-like cells.