Translocation of the testicular estradiol receptor is not an obligatory step in the gonadotropin-induced inhibition of C17-20-lyase.
We have investigated the effects of hCG and estradiol on the time course of the inhibition of C17-20-lyase and the depletion of the estradiol cytosol receptor in testicular tissue of male rats. In hCG-treated animals the first significant decrease in C17-20-lyase activity was observed 16 h after injection of the hormone. The C17-20-lyase activity decreased further during the following 56 hours. Estradiol-cytosol receptor levels were significantly decreased 7 hours after the hCG injection, and after a nadir at 16 hours increased to 130% of control values at 72 hours. In contrast, in the estradiol-treated animals the first significant inhibition of C17-20-lyase activity could be observed only after 24 h, while a 95% depletion of estradiol-cytosol receptor levels was observed already within 1 h after administration of the hormone. These results demonstrate that a rapid estradiol-induced depletion of the estradiol receptor as such does not necessarily result in a subsequent immediate inhibition of the C17-20-lyase. The rapid inhibition of this enzyme after hCG indicates, therefore, that other mechanisms are involved.
D000446:Aldehyde-Lyases / Q000037:antagonists & inhibitors*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D003600:Cytosol / Q000378:metabolism; D004958:Estradiol / Q000378:metabolism* / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011959:Receptors, Estradiol; D011960:Receptors, Estrogen / Q000187:drug effects / Q000378:metabolism*; D013254:Steroid 17-alpha-Hydroxylase; D013737:Testis / Q000187:drug effects / Q000378:metabolism*
D006063:Chorionic Gonadotropin; D011959:Receptors, Estradiol; D011960:Receptors, Estrogen; D004958:Estradiol; D013254:Steroid 17-alpha-Hydroxylase; D000446:Aldehyde-Lyases