We investigated the gestational expression of androgen receptor (AR) and defined its regulation and that of its co-repressors, PSF and p54nrb, by steroid hormones and myometrial stretch in vivo in pregnant and non-pregnant rats. Our data demonstrate that, 1) myometrial AR expression decreases prior to term; 2) AR expression is up-regulated by MPA treatment and down-regulated by mechanical stretch; (3) myometrial PSF protein expression is down-regulated by estrogen signaling and by mechanical stretch, and up-regulated by androgen signaling; (4) while myometrial PSF mRNA expression is also down-regulated by stretch, the regulation by estrogen and P4 on PSF mRNA appear to be opposite to the effects on PSF protein. We conclude that the decreased androgen signaling in late pregnancy (as a result of decreased AR and PSF expression mediated by hormonal and mechanical signals) may contribute to the mechanisms leading to labor initiation.

We investigated the gestational expression of androgen receptor (AR) and defined its regulation and that of its co-repressors, PSF and p54nrb, by steroid hormones and myometrial stretch in vivo in pregnant and non-pregnant rats. Our data demonstrate that, 1) myometrial AR expression decreases prior to term; 2) AR expression is up-regulated by MPA treatment and down-regulated by mechanical stretch; (3) myometrial PSF protein expression is down-regulated by estrogen signaling and by mechanical stretch, and up-regulated by androgen signaling; (4) while myometrial PSF mRNA expression is also down-regulated by stretch, the regulation by estrogen and P4 on PSF mRNA appear to be opposite to the effects on PSF protein. We conclude that the decreased androgen signaling in late pregnancy (as a result of decreased AR and PSF expression mediated by hormonal and mechanical signals) may contribute to the mechanisms leading to labor initiation.