EFFECTS OF GONADOTROPINS ON STEROID-SECRETION BY INFANTILE AND JUVENILE MOUSE OVARIES INVITRO

The steroidogenic potential of ovaries from infantile and juvenile mice was analyzed using organ culture with defined medium. In initial experiments, pieces of ovaries from 2, 7, 11, 15 and 20 day old B6D2F1 mice were cultured in medium without added hormones or with 2 .mu.g biological grade FSH [follitropin] (NIAMDD-rat FSH-B-1)/ml for 48 h, and the media were subsequently analyzed by RIA [radioimmunoassay] for progesterone [P], testosterone [T], 17.beta.-estradiol [E2] and androstenedione. Ovaries from 2 day old mice did not secrete detectable quantities of these steroids and secretion was not stimulated by FSH. In the other 4 age groups, biological grade FSH greatly increased the secretion of all 4 steroids compared with the controls. The remaining experiments focused on the 7 day old mice. To determine whether FSH or contaminating LH [lutropin] in the biological grade FSH stimulated steroid secretion, pieces of 7 day old ovaries were cultured in medium without added hormones or with 100 ng/ml of the following purified gonadotropins: LH (NIAMDD-rat LH-I-4), FSH (NIAMDD-rat FSH-I-3) and LH plus FSH. Although purified FSH slightly stimulated T and P secretion, purified LH stimulated T and P secretion to the same extent as the biological grade FSH and the combination of LH plus FSH. Both purified LH and FSH stimulated E2 secretion (P < 0.005), but the combination of the 2 purified gonadotropins stimulated significantly more (P < 0.005) estradiol secretion than either alone. Ovaries incubated with FSH plus T, but not with FSH plus DHT ([dihydroxytestosterone] a nonaromatizable androgen), secreted levels of E2 comparable to those produced in the presence of FSH and LH. In 7 day old mouse ovaries, LH promotes E2 production by stimulating the synthesis of androgen precursor, which is subsequently aromatized in response to FSH. Light and EM examination of fresh and cultured ovaries from 7 day old mice showed that follicles contained 1 or 2 layers of granulosa cells surrounded by a clearly defined theca. No differentiated interstitial tissue was observed. In immature mouse ovaries 7 days of age or older, steroid production in vitro can be stimulated with gonadotropins; as early as 7 days of age, LH and FSH interact to promote E2 production.