Interactions of 17 beta-estradiol and L-epinephrine on the rat uterus.

Abstract

Epinephrine diminished in vitro uptake of 3H-estradiol by the uterus of spayed rats treated with estradiol (2 µg) for 3 days. This effect was observed at 15 min in the cytosol and at 30 min in the nuclear fraction. Epinephrine did not show any action when incubated with uterine homogenates suggesting that in order to act this catecholamine requires an intact tissue or a complete cellular structure. The in vivo uptake of 3H-estradiol and determination of the number Binding sites of binding sites were performed in the uterus of rats treated with different amounts of estradiol and estradiol plus epinephrine for 3 days. Epinephrine alone had no effect, but epinephrine plus 0.4 µg of estradiol decreased uptake of 3H-estradiol and the number of binding sites, although the dose of 2 µg of estradiol increased these two parameters. The increase in estradiol uptake and the number of binding sites produced by epinephrine when the large dose of estradiol was utilized could be explained by the effects obtained by injecting estradiol alone; this shows that larger amounts of estradiol decreased uptake and number of binding sites. These results suggest that epinephrine decreases both in vitro and in vivo the influx of estradiol into the rat’s uterus.