[The effect of sex hormones on calcium ion transport in the myometrial cells in rabbits].

The effect of estradiol, progesterone, and testosterone on calcium ion transport was studied in the rabbit uterus. To investigate the effect of sex hormones on voltage-dependent calcium channels, the isolated uterus was incubated in Ca2(+)-free depolarizing K+ solution. In this solution cumulative dose-response curves to CaCl2 were obtained by increasing the Ca2+ concentration (10(-5)-10(-3) mol.l-1). A decrease of the maximal contractile response to CaCl2 was recorded after in vitro pretreatment with estradiol (1.8 x 10(-5) mol l-1), (6.4 x 10(-1) mol) and testosterone (5.8 x 10(-5) mol.l-1). The pD2 values were unchanged. The possibility of affecting calcium ion release from intracellular stores by sex hormones was observed indirectly on using Ca2(+)-free Tyrode's solution with 0.8 nmol EDTA. Contractile responses of the isolated uterus were induced by single application of norepinephrine (NE) in the dose of 2 x 10(-4) mol.l-1. Pretreatment with sex hormones decreased the contractile responses of the uterus to NE. The obtained results suggest an important involvement of calcium ions in the mechanism of action of sex hormones upon the myometrial smooth muscle.