CELL MEMBRANE GPER AND ERα ON MYOMETRIUM: TWO DISTINCT RECEPTORS WITH DISTINCT SIGNALLING PATHWAYS

The “rapid” effects of oestrogens on myometrium mainly result by activating cell membrane oestrogen receptors: ERα and GPER (G protein coupled oestrogen receptor 1). In contrast to the contractile effect induced by G-1 (GPER agonist), effect involving the opening of L-type calcium channels, oestradiol (E 2 ) inhibited until arrest the spontaneous contractile activity and significantly decreased the contraction induced by high K + or oxytocin. The effects of E 2 were not blocked by G-15 (GPER antagonist). We concluded that the “rapid” effects E 2 -induced on myometrium are the result of cell membrane ERα activation and mainly consist of the inhibition of L-type calcium channels. It is a sticking difference between the genomic and non-genomic effect of E 2 on oxytocin-induced signalling pathway. Finally, it is very probable a masking/inhibition (modulator) effect of ERα on cell membrane GPER activity.