Effect of estradiol, progesterone, and progestogens on calcium influx in cell cultures of human vessels

The effect of estradiol, progesterone, and three progestogens on calcium influx was investigated in cell cultures of human vessels under resting conditions. Estradiol significantly inhibited calcium influx in endothelial and smooth muscle cells at concentrations of 10(-6) and 10(-7) M. Neither progesterone nor the progestogens chlormadinone acetate, dienogest, and norethisterone showed a significant effect on calcium influx. In equimolar combinations with estradiol progesterone, chlormadinone acetate, and dienogest did not influence the effect of estradiol in either cell type tested. In contrast, norethisterone attenuated the effect of estradiol in both cell types. The effect of estradiol in smooth muscle cells signifies that estradiol could produce vasodilation by this mechanism. The significance of the effect on endothelial cells is less clear. Further research is required to elucidate whether estradiol is able to block activated cell calcium channels and, if so, which types of channel.