INTERFERENCE OF GESTAGENS AND ANDROGENS WITH RAT UTERINE OESTROGEN RECEPTORS

Abstract

The inhibitory effect of some gestagens and calusterone on the binding of oestradiol-17β 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-17β 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-17β to specific uterine receptors in vivo. Results from a Scatchard plot analysis suggest that the interference with the binding of oestradiol-17β caused by both progestogens and calusterone is due to a non-competitive interaction.