Molecular distribution profiles for FSH in anterior pituitary extracts or serum of infantile female rats (10–12 days of age), as determined by exclusion chromatography, were compared to those of prepubertal (27 days) or adult (70 days) rats. The elution position of pituitary FSH at the different ages studied was essentially the same, indicating the absence of major differences in average apparent molecular size. Characterization of serum FSH revealed a preponderance of FSH components of larger molecular size. However, the elution position of serum FSH was similar at all ages studied. Small quantitative differences were found between pituitary FSH potencies assessed by RIA or by bioassay. However, at the two ages studied (12 and 27 days) the immunoassay/bioassay ratios were similar. Pituitary FSH of both infantile and older female rats showed a dose-response curve in the ovarian hCGaugmentation assay parallel to that of NIH-FSH-S11. Ovaries from 29 day old rats transplanted to other prepubertal animals (23 days of age), i.e., an age in which serum FSH levels have already declined, failed to show follicular or interstitial development 7 days later. By contrast, ovaries transplanted to 8 day old female rats, i.e., an age in which serum FSH is elevated and still rising, showed interstitial stimulation and development of antral follicles. Lyophilized serum of 12 day old rats microinjected into the periovarian space of HCGtreated rats induced an increase in ovarian weight significantly greater than that produced by serum of older rats. The results indicate that both pituitary FSH and the elevated circulating FSH levels detected by RIA in the infantile female rat possess a biological activity compatible with the expected activity based on RIA studies. In addition, the molecular forms of FSH in infantile rats appear to be similar to those of older animals.
ASJC Scopus subject areas