HORMONAL-REGULATION OF ACTIVITIES OF 17-BETA-OL-DEHYDROGENASES, AROMATASE AND 4-ENE-5-ALPHA-REDUCTASE IN IMMATURE RAT OVARIES

Female rats were hypophysectomized at 21 days of age, and after 3 days, the hypophysectomized rats in groups of 3-20 were injected daily with 10 μg of NIH-LH-S19, 10-100 μg of NIAMD-Rat-FSH-B-1, 20 μg of oestradiol-17β or saline for 3 days. Ovarian homogenates from these rats and intact rats at 27 days of age were incubated with [14C]-4-androstene-3,17-dione, [14C]-oestrone, [7-3H]-4-androstene-3,17-dione or [7-3H]-progesterone and enzyme activities and metabolism of progesterone were estimated. The activities of 5α-reductase, testosterone and oestradiol 17β-ol-dehydrogenases and aromatase decreased significantly 6 days following hypophysectomy. A distinct response to LH but not to FSH in the 5α-reductase activity in the hypophysectomized rat ovary was found. On the other hand, the activities of 17β-ol-dehydrogenases and aromatase in the hypophysectomized rat ovary were stimulated (10 to 200 times) by FSH but not by LH. No stimulation of these enzyme activities by oestradiol- 17β was involved. The formation of oestradiol-17β from progesterone could be demonstrated only in the FSH-injected rat ovary. These results show that the 5α-reductase activity is regulated by LH and the activities of 17β-oldehydrogenases and aromatase are regulated by FSH in immature rat ovaries. It is also suggested that nonresponse to LH and response to FSH of the uterus of hypophysectomized immature rats can be explained in part by the present results. © 1979.