Increase by oestrogen of calcium entry and calcium channel density in uterine smooth muscle.

1 The effect of in vivo oestrogen treatment on both 45Ca influx in myometrial strips and the kinetics of [3H)-nitrendipine binding in the isolated plasma membrane (PM) was studied. 2 After four days of continuous oestrogen treatment of ovariectomized rats, 45Ca influx in both resting (unstimulated) and K-stimulated myometrium was substantially increased. 3 Oestrogen treatment significantly increased the density in PM of nitrendipine binding sites and also caused a slight and insignificant increase in the affinity for nitrendipine. 4 The data suggest that the increase in Ca entry following oestrogen treatment probably results from an increase in calcium channel density.