Human chorionic gonadotropin causes an estrogen-mediated induction of rat ovarian carbonyl reductase

We earlier reported that human chorionic gonadotropin (hCG) stimulates rat ovarian carbonyl reductase (CR) activity and content, and that estrogen enhances the stimulatory effect. The present study was performed to determine the mode of action of the gonadotropin. Cycloheximide (CHX) and actinomycin D (AD) were given to estradiol-pretreated immature rats 6 h before hCG treatment. The enzyme activity was measured with three substrates, and the enzyme content was determined by the method of Western-blot analysis using anti-rat ovarian CR anti-serum as the first antibody. Both protein inhibitors significantly prevented hCG from increasing the enzyme activity and content in estradiol-pretreated ovary. These results indicate that rat ovarian CR is induced by LH via the action of estrogen.