Changes in the Isoelectric Focusing Profile of Pituitary Follicle-stimulating Hormone in the Developing Male Rat 1

Abstract

Pituitary glands, hypothalami, and trunk blood were obtained from male rats at 5, 15, 18, 21, and 29 days of age, on the day of balanopreputial separation (Days 42-45), and during adulthood. The forms of follicle-stimulating hormone (FSH) present within each pituitary were separated by polyacrylamide gel isoelectric focusing. Serum and pituitary gonadotropins, hypothalamic luteinizing hormone-releasing hormone (LHRH), and the profile of FSH forms across the isoelectric focusing gel were determined by radioimmunoassay. No change in the relative proportions of FSH forms were observed between 5 and 21 days of age. Likewise, only slight changes in serum and pituitary gonadotropin levels and hypothalamic LHRH content were observed at these times. After 21 days of age, dramatic increases in serum and pituitary gonadotropin levels were observed. Similarly, a shift in FSH forms within the pituitary to more basic and bioactive forms was observed at this time. These results demonstrate that, during the transition through puberty in the male rat, not only the absolute amount, but also the isoelectric focusing profile, of FSH change.

Structural and Functional Roles of FSH and LH as Glycoproteins Regulating Reproduction in Mammalian Species

“…This is consistent with data from rats where an increase in bioactive forms of FSH within the pituitary was observed during the transition through puberty [96,97]. However, in heifers Stumpf et al [29] failed to detect a change in the distribution of either LH or FSH isoforms in pituitaries collected during sexual maturation.…”

Active immunization of cattle against partly purified follicular fluid from sheep

“…Cummins et al (1986) pointed out that differences in FSH secretion after immunization of ewes could be observed in an homologous RIA, but not in a heterologous assay. This may reflect differences in the molecular species of FSH secreted, as has been reported for the rat (Foulds & Robertson, 1983;Chappel & Ramaley, 1985), hamster (Chappel, 1981) and monkey (Chappel et al, 1984). The modulation of such forms of FSH in cattle and sheep may provide a further role for inhibin, and for other mechanisms of controlling differen¬ tial LH and FSH secretion.…”

Bioactive Follicle-Stimulating Hormone Levels in Serum and Urine of Male and Female Rats from Birth to Prepubertal Period1

“…FSH from pituitaries of monkeys before and after castration displayed differing bio-to immuno-FSH activities and had different molecular sizes. Discrepancies in FSH B/I ratios were also reported in pituitaries of rats under many endocrine states using in vivo and in vitro FSH bioassays (Diebel et al, 1973;Muchopadhyay et al, 1979;Chappel et al, 1983a;Chappel and Ramaley, 1985). Recently, FSH bioactivities in human serum have been analyzed with the present cultured granulosa cell assay (Dahl et al, 1986(Dahl et al, , 1987aTenover et al, 1987), or a cultured Sertoli cell assay (Padmanabhan et al, 1987).…”