Effects of steroids and gonadotropins on follicular development in the hypophysectomized hamster.

Abstract

AbstractTo determine the rate of follicular development in long‐term hypophysectomized (H) hamsters, single IP injections of 3H‐thymidine were given six days after H and autoradiographs were prepared from animals killed on days 6–15. Only follicles in stages 1 (2–3 layers of granulosa cells), 2 (4–5 layers) and 3 (6–7 layers) were present and there were fewer follicles than in intact, cyclic hamsters. The entire population of follicles in stages 1 and 2 was replaced every five to six days in hypophysectomized hamsters, whereas in cyclic hamsters, complete turnover takes eight days (Chiras and Greenwald, '77).Other groups of H hamsters were treated on days 4–6 with either estradiol benzoate (EB — 10 μg), progesterone (P — 1 mg) or EB and P and then given 3H‐thymidine at 0900 hours of day 6 and killed one hour later. Steroid treatment affected early stages of follicular development: EB stimulated growth of these follicles; P alone had little effect; given with EB, P acted as an antagonist.Other H hamsters were treated with FSH (100 μg), LH (10 μg), FSH + LH, PMS (30 IU) or saline vehicle at 0900 hours six days post‐hypophysectomy. They were injected with 3H‐thymidine at 2100 hours on day 6 and killed one hour later. LH‐ and saline‐treated animals had approximately the same number of follicles; however, there were no stage‐3 follicles in the LH‐treated group and the percentage of labelled follicles in stages 1 and 2 was significantly lower after LH treatment. FSH enhanced follicular development and thymidine uptake. Twice as many stage‐3 follicles were seen in FSH‐treated animals as controls; stage‐4 follicles (>8 layers of granulosa cells) were also encountered after FSH treatment. Labelling Index (LI) and Intensity (L. Int.) for the FSH‐treated group were the highest of all treatments. LH antagonized some of the effects of FSH. PMS resulted in follicular growth similar to that achieved by FSH; however, PMS markedly depressed LI and L. Int., which was probably due to the LH‐like component of PMS. These results demonstrate that the gonadotropins affect the development of small follicles. FSH stimulates growth; LH depresses follicular growth when administered alone and antagonizes some of the effects of FSH.Hamsters pretreated with EB or P on days 4–6 and then given a single, subcutaneous (SC) injection of FSH at 0900 hours on day 6, were treated with 3H‐thymidine at 2100 hours on day 6 to assess the interaction of steroids and FSH. EB pretreatment caused the development of stage‐5 follicles (early antral follicles) but did not increase thymidine uptake (measured by LI and L. Int.) in the small follicles above that attained by FSH alone. P pretreatment diminished thymidine uptake in small follicles, but did not reduce their number.These results demonstrate that in the hamster the population of small follicles, i.e., the often misnamed “pituitary‐independent” follicles, can be influenced quantitatively and qualitatively by steroids and gonadotropins.