Estrogen Regulation of Follicle Stimulating Hormone in Cell Cultures of Sheep Pituitaries1,2

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Abstract
Cell cultures of ovine pituitaries were maintained for up to 3 wk. A specific double antibody radioimmunoassay was used to measure FSH [follicle stimulating hormone] in the media and cells. The rate of FSH synthesis increased in the cultures during the first 4-6 days to a level of approximately 50 ng/day per 106 cells, generally remained constant for 2 wk and then decreased. The FSH produced in vitro migrated similarly to highly purified ovine FSH on P-60 polyacrylamide gel filtration columns and had a biological potency essentially identical to that of the highly purified FSH standard. Addition of 17.beta.-estradiol (E2) at 10-9 M on days 2 or 6 of incubation decreased FSH synthesis > 95% within 30 h. Time-course analysis revealed that the effect of E2 can be observed as early as 6 h after treatment. FSH synthesis resumed after removal of E2 and reached control levels within 6 days. The lowest effective dose of E2 was 10-11 M; E2 at 5 .times. 10-11 M maintained FSH production at approximately 50% of the control levels. Diethylstilbestrol was as active, estriol was 1/10th as active, and 17.alpha.-estradiol was 1/100th as active as E2. Progesterone (P), 5.alpha.-pregnane-3,20-dione (5.alpha.DHP), 20.alpha.-hydroxy-pregn-4-en-3-one (20.alpha.-OHP), testosterone, 5.alpha.-dihydrotestosterone and corticosterone had no effect on FSH levels. Estrogen is probably capable of playing a major role in FSH synthesis and release by action directly at the pituitary level.
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