Follicular fluid stimulation of estrogen secretion by immature porcine granulosa cells.

Fluid from large (6-12 mm) porcine follicles (LFFl) enhanced estrogen secretion by granulosa cells from small (1-2 mm) antral porcine follicles during 3-day incubations. Shorter incubations with LFFl or of any length with fluid from small follicles were inconsistent in elevating estrogen secretion. Estrogen was undetectable in freshly collected cells. Addition of 0.14-0.7 micrograms/ml androgens increased estrogen secretion but addition of androgen in a concentration equivalent to that in charcoal-treated LFFl (140 pg/ml) did not. FSH stimulated progesterone but not estrogen secretion. Pretreatment with FSH did not enhance LFFl stimulation of aromatase activity, nor did pretreatment with LFFl influence FSH action on aromatase. These observations suggest the presence of an aromatase stimulator in fluid from nonatretic follicles. By stimulating estrogen production the factor might contribute to follicle development and prevent an increase of the androgen/estrogen ratio which has been proposed to influence atresia.