Inhibitory effect of 17 β -estradiol on prostaglandin E 2-induced phosphoinositide hydrolysis in osteoblast-like cells

Abstract

We examined the effect of estradiol on PGE 2-induced phosphoinositide hydrolysis and cAMP production in cloned osteoblast-like MC3T3-E1 cells. 17 β -Estradiol pretreatment significantly inhibited the formation of inositol phosphates induced by 10 μM PGE 2 in a dose-dependent manner between 1 pM and 10 nM. This effect of 17 β -estradiol was dependent on the time of pretreatment and submaximum inhibition was observed at 4 h. However, 17 β -estradiol had little effect on the formation of inositol phosphates induced by 20 mM NaF, a GTP-binding protein activator. The cAMP production induced by PGE 2 was not influenced by 17 β -estradiol. These results suggest that 17 β -estradiol modulates the signal transduction by PGE 2 and that the effect seems to be exerted between PGE 2 receptor and the GTP-binding protein coupled to phospholipase C in osteoblast-like MC3T3-E1 cells.