Aromatase activity in human granulosa cells during follicular development and the modulation by follicle-stimulating hormone and insulin.

Granulosa cells were isolated from follicles that ranged in size from 0.4 to 2.0 cm in diameter, obtained from patients during the follicular phase of the menstrual cycle. Aromatase activity, assessed by the release of tritiated water from [1 beta-3H]testosterone, was undetectable in follicles with a diameter of less than 1.0 cm; thereafter, there was a direct correlation between aromatase activity and follicular diameter. When cultured in the presence of 200 ng of National Institutes of Health follicle-stimulating hormone-15 per milliliter, aromatase activity was stimulated in cells isolated from all sizes of follicles from 0.4 to 1.5 cm. Insulin (500 ng/ml) further augmented follicle-stimulating hormone (FSH)-induced aromatase activity, as evidenced both by an increase in 17 beta-estradiol production and by the release of tritiated water from [1 beta-3H]testosterone by granulosa cells. This study further delineates the role of FSH in estrogen production during human follicular development and suggests that insulin or insulin-like growth factors may play a role in modifying the FSH-dependent cellular differentiation of human granulosa cells.