Oestriol and oestradiol increase cell to cell communication and connexin43protein expression in human myometrium

Oestradiol increases the protein expression of connexin43 (Cx43) gap juncti ons in myometrium but the effect of oestriol on gap junction expression has not been described previously. Oestriol is the most abundant free oestroge n in pregnant women and there is a marked surge in oestriol concentrations before term and idiopathic preterm labour. In order to determine whether oe striol may have a physiological action on the myometrium, cultured human my ometrial cells obtained from non-pregnant hysterectomy specimens were expos ed to 10 nmol/l oestradiol or oestriol, Intercellular communication between myometrial cells was investigated by microinjection of confluent cultured cells with the gap junction-permeant tracer Cascade Blue, There was a progr essive increase in coupling after exposure to oestradiol or oestriol (P < 0 .0005), An increase in Cx43 protein expression was demonstrated by immunocy tochemistry after 1 h (P < 0.01) and 3 days (P < 0.01) exposure, and by Wes tern blotting after 1 h (P < 0.01) and 3 days (P < 0.05) exposure, to both oestradiol and to oestriol, We conclude that oestriol increases gap junctio n communication in human myometrium by increasing gap junction expression. Elevated oestriol concentrations may thus play a role in the initiation of labour in women, by increasing cell-cell communication in the myometrium.