Interference of gestagens and androgens with rat uterine oestrogen receptors

Abstract

The inhibitory effect of some gestagens and calusterone on the binding of oestradiol-17beta to its specific uterine receptors has been investigated in intact rats. Progesterone, medrogestone, clogestone, medroxyprogesterone acetate and calusterone reduce the specific oestradiol-receptor interaction in vitro; this effect is dose-dependent and does not differ significantly from one drug to the other. A more relevant decrease in the amount of oestradiol-17beta bound to specific receptors has been observed with calusterone. Progesterone, clogestone, medrogestone, medroxyprogesterone acetate and calusterone given orally induce a marked decrease (between 30 and 70% depending on the dose) in the binding capacity of oestradiol-17beta to specific uterine receptors in vivo. Results from a Scatchard plot analysis suggest that the interference with the binding of oestradiol-17beta caused by both progestogens and calusterone is due to a non-competitive interaction.

PIP: The inhibitory effect of some gestagens and calusterone on the binding of estradiol-17beta to its specific uterine receptors has been investigated in intact rats. Progesterone, medrogestone, clogestone, medroxyprogesterone acetate and calusterone reduce the specific estradiol-receptor interaction in vitro; this effect is dose-dependent and does not differ significantly from 1 drug to the other. A more relevant decrease in the amount of estradiol-17beta bound to specific receptors has been observed with calusterone. Progesterone, clogestone, medrogestone, medroxyprogesterone acetate and calusterone given orally induce a marked decrease (between 30 and 70% depending on the dose) in the binding capacity of estradiol-17beta to specific uterine receptors in vivo. Results from a Scatchard plot analysis suggest that the interference with the binding of estradiol-17beta caused by both progestogens and calusterone is due to a noncompetitive interaction.