Ovaries of neonatal rats were transplanted on the day after birth into ovariectomized (high gonadotrophin levels) or ovariectomized-hypophysectomized adult female rats (extremely low gonadotrophin levels). Although transplantation caused a reduction of the number of growing follicles in all transplants, it did not seem to induce a clearly abnormal course of follicle development. After 15 days of development, the hormone-rich transplants contained a greater number of follicles larger than type 4 and a smaller number of oocytes with diameters less than 21 micrometers, than did the hormone-poor transplants. In the transplants with high hormone levels, the smallest follicles (types 2--3a) showed advanced transition of flattened into cuboidal follicle cells and oocyte growth. It is concluded that in these experimental conditions gonadotrophins, presumably especially FSH, seem to have a stimulatory effect on early follicle cell development and early oocyte growth.
SUMMARYTo determine whether the high FSH levels present before day 20 in female rats are of importance for normal follicular development, the effect of depression of FSH levels on numbers of medium and large follicles was studied. Two Injection of antiserum to FSH from day 7 till day i i resulted in a decreased number of large follicles on day 12 . The same treatment given from day i till day 15 or from day r 5 till day 19 did not induce this effect, although one injection on day I or day r 5 induced atresia in many large follicles one day later. This acute effect seems to be compensated within five days.The present results support the view that the high gonadotrophin levels (especially FSH) before day 20 are a requirement for normal follicular development.
To investigate the significance for ovarian maturation of the high FSH levels present in immature female rats before Day 20 after birth, the effect of suppression of these high FSH levels by repeated injections of 5cs-dihydrotestosterone propionate (DHTP)
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