[Modulation of uterine contractile activity by steroid sex hormones. Review].

Sexual steroids play an important role in the regulation of contractile uterine activity. Progesterone has shown a relaxant effect on rabbit, rat and human uterus. In addition it has been reported that 5 beta-reduced metabolites are more potent than their precursor in the rat uterus. In the regard to their mechanism of action it is known they act by means of a non-genomic mechanism and it has not been identified a some data suggest steroids inhibit calcium influx to muscular cell by blockade of voltage- and/or receptor- operated channels. Regulation of uterine contractility by steroid hormones during sexual cycle and pregnancy suggest an important physiologic role by inducing a quiescent state necessary for maintaining of pregnancy.