Stimulatory action of follice-stimulating hormone on estradiol-17 beta secretion by hypophysectomized rat ovaries in organ culture.

Ovaries of rats explanted in organ culture 2-3 days after hypophysectomy at 26 days of age synthesize ans secrete estradiol-17beta into the culture medium at approximately linear rates for 48 h. Addition of testosterone (5 times 10- minus 7M) to the culture medium occasionally caused small increases of up to 50 percent in rate of estradiol production. Significant increases (60-200 percent) in estradiol secretion resulted from addition of two different FSH preparations, in concentrations as low as 0.25 mug/ml in the absence of testosterone. In the presence of testosterone, the same FSH preparation caused much more marked increases in estradiol secretion of up to 900 percent. In the absence of testosterone, two different luteinizing hormone preparations failed to increase estradiol secretion significantly, although in the presence of testosterone, small increases were sometimes observed. It is concluded that FSH regulates estradiol biosynthesis in the hypophysectomized rat ovary by a specific stimulatory action on the aromatizing enzyme system.