Estrogen Regulation of Follicle-Stimulating Hormone Productionin Vitro:Species Variation*

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Abstract
Pituitary cell cultures were used to investigate factors, such as species, sex, and age, which might be associated with differences in FSH regulation by estrogens. 17β-Estradiol at 10-9 M inhibited spontaneous secretion of FSH in sheep, pig, and cow cell cultures (65–95%), had no detectable effect on rabbit cell cultures, and stimulated spontaneous secretion of FSH in rat cell cultures (1.5- to 5-fold). These differential effects of 17β-estradiol were not due to changes in cell division; gonadotrophs id not divide in culture, and general cell division was unaffected by 17β-estradiol. Differences in 17β-estradiol action on FSH secretion were not associated with age or sex. Spontaneous secretion of FSH from pituitary cell cultures also varied according to species and was ranked: rabbit ≅ sheep > pig > rat » cow. Secretion and synthesis of FSH were tightly coupled in at least three of these species. Nonestrogenic steroids, such as androgens, progestins and corticosterone, exhibited only minor effects on spontaneous secretion of FSH in either male or female sheep cell cultures. These results clearly show that estrogens are capable of altering FSH secretion and synthesis differentially in pituitary cell cultures from different species. It is possible that the differences noted in pituitary cell cultures from various species also exist in vivo.