Sexual Maturation in Female Rats: Time-Related Changes in the Isoelectric Focusing Pattern of Anterior Pituitary Follicle-Stimulating Hormone 1

Abstract

Anterior pituitary glands (AP) were obtained from female rats at 5, 15, 18, 21 and 29 days of age, at the time of vaginal opening (VO) and during adulthood on proestrus. The multiple species of follicle-stimulating hormone (FSH) present within the AP were separated by the technique of polyacrylamide gel isoelectric focusing (PAG-IEF) and measured with the NIAMDD rat FSH radioimmunoassay kit. AP's obtained from immature female rats prior to VO contained elevated levels of total FSH as well as all of the species of AP FSH observed in adult rats (and hamsters). However, the majority of the FSH immunoactivity migrated to the most acidic portion of the gel (isoelectric point [pI] value=4.2-3.8). At the time of VO and during adulthood, a decrease in total AP FSH was observed. In addition, a shift in the relative proportions of certain FSH species occurred. The AP's of adult animals contained relatively greater amounts of more basic (pI values 6.0-5.0) forms of FSH compared with immature animals. When each of the AP FSH species isolated from adult animals was tested in a radioligand receptor assay, the most acidic (pI=4.2-3.8) failed to interact with the receptor preparation, while those with pI values from 6 to 4.7 were able to compete with [125I]-labeled FSH for receptor binding in a parallel fashion. Thus, the observed shift in the PAG-IEF FSH profiles to more basic (and biologically active) forms may represent a change in the composition of AP FSH that serves an important role in the maturation process leading to ovulatory cyclicity.

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.…”

Circulating FSH isoform patterns during recurrent increases in FSH throughout the oestrous cycle of heifers

“…2 (Padmanabhan 1988;Wide and Naessen, 1994) and men (Matikainen et al, 1994 (Chappel et al, 1983;Wide 1989). Many studies using GnRH antagonists (Kessel et al, 1988;Mortola et al, 1989;Matikainen et al, 1992), GnRH agonist (Kessel et al, 1988) …”

Efficacy of a combined protocol of urinary and recombinant follicle-stimulating hormone used for ovarian stimulation of patients undergoing ICSI cycle

“…It has been shown that gonadotropin isoforms influence a variety of biological activities, cellular growth and development, steroidogenesis and protein synthesis [37][38][39]. Because of their structural differences, FSH isoforms differ in their ability to bind to target cell receptors surviving in the circulation and induce a biological response in vivo and in vitro [40][41][42][43][44]. Evident differences between recombinant and urinary FSH were recognized, rFSH contains a higher proportion of less acidic isoforms, whereas urinary FSH contains a higher proportion of acidic forms.…”