Abstract
The effects of estrogens on ovarian aromatase activity were investigated in vitro using granulosa cells from immature hypophysectomized estrogen-primed rats. The cells were cultured for 3 days in an androgen-free medium in the presence of follicle-stimulating hormone (FSH), with or without the specified estrogen. After washing, the cells were reincubated for 5 h with 10(-7) M androstenedione, and the formation of estrogens was measured. Estrogen production by control and diethylstilbestrol-treated cells was negligible, while FSH stimulated aromatase activity. Furthermore, concomitant treatment with diethylstilbestrol led to dose-dependent increases in the FSH-induced aromatase activity with an ED50 value of 4 X 10(-9) M and an apparent Vmax value 12- to 16-fold higher than those induced by FSH alone. The direct stimulatory effect of estrogens was time-dependent and was not accounted for by increases in cell protein. Various native and synthetic estrogens also augmented the FSH induction of aromatases (native estrogens: estradiol-17 beta = estrone greater than estradiol-17 alpha greater than estriol; synthetic estrogens: hexestrol greater than moxestrol greater than ethinyl estradiol much greater than chlorotrianisene and mestranol). The effect of estradiol-17 beta was dose-dependent with an ED50 value of 9 X 10(-9) M, which is within the physiological levels of follicular estradiol-17 beta. Although treatment with androgens also enhanced the FSH-induced aromatases, treatment with a progestin (R5020) or a mineralocorticoid (aldosterone) was without effect. Thus, estrogens directly augment the stimulation of granulosa cell aromatase activity by FSH. Follicular estrogens may activate intraovarian autoregulatory positive feedback mechanisms to enhance their own production, resulting in selective follicle maturation and the preovulatory estrogen surge.
Highlights
The cells were cultured for3 days in anandrogen-free [8],the possible involvement of estrogens has notbeen studmedium in thepresence of follicle-stimulating hormone (FSH), with or without the specified estrogen
Effect of Other SteroidHormones on the FSH Induction of Aromatase Activity-To examine the specificity of the stimulatory effect of diethylstilbestrol, granulosa cells were cultured for 3 days in the presence or absence of FSH (10 ng/ml) with or without M of diethylstilbestrol, dihydrotestosterone, R1881, or aldosterone (Fig. 2)
Induction of Aromatase Activity-To evaluate the effect of treatment with synthetic estrogens on the FSH inductionof aromatase activity,granulosa cells were cultured for 3 days in the presence or absence of FSH (10 ng/ml) with or without increasing concentrations (10"o-10-7 M) of various synthetic estrogens(Fig. 5, A and B )
Summary
L-glutamine(2mM),penicillin (100units/ml) andstreptomycin sulfate To evaluate the effect of treatment with diethylstilbestrol (a (100 pg/ml). To examine the degree of cross-reactivity of the various test compounds in the estrogen radioimmunoassay, granulosa cells were cultured in the presence or absence of FSH, with or without increasing concentrations (10""-10-7 M) of the test compounds. After 3 days, the cells were washed twice with 2-ml portions of medium and reincubated for an additional 5 h with or without androstenedione, thereby estimating the relative contribution of the endogenous estrogens and of the test compounds tothe total estrogen immunoreactivity. C, cellular protein content was determined after the 5-h incubation using controls; DES, diethylstilbestrol
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