Electrofocusing fractionation of follicle stimulating hormone in pituitary cell culture extracts from male and female rats

Abstract

Three-day pituitary cell cultures from adult male and female rats were incubated for 4 h in the presence of 10 nM LHRH and the molecular heterogeneity of FSH was assessed in the media of LHRH-stimulated cells and in cell extracts from unstimulated cells using an electrofocusing technique. The pi distribution of FSH showed a high degree of similarity between cell media and cell extracts of each sex although differences were observed between sexes. Pituitary cell cultures from male rats were also incubated in the presence of 10 −8 M testosterone and 10 −8 M estradiol and the pI distribution of FSH from media after LHRH stimulation was determined. No significant differences in the pI profiles were observed. Incubation with charcoal-treated bovine follicular fluid (an inhibin source) resulted in a significant reduction in recovered FSH activity in the pH region 3.61-3.92 although this decrease did not markedly alter the pI profile of FSH. Close similarities were observed in the pI distribution of FSH of pituitary cell culture extracts and pituitary gland extracts from intact animals of both sexes, however, differences in pi distribution were noted in pituitary extracts in the male but not the female following gonadectomy. It is concluded that (1) stored FSH is released from the pituitary without major modification to its structure as assessed from its pI profile, (2) sex differences in the pI profile of FSH in pituitary extracts are retained in culture and following LHRH-stimulated release, (3) the pI distribution of FSH is not affected by testosterone or estradiol and only minimally by inhibin in short-term cultures. It is thus suggested that the failure to observe in vitro an effect of steroids on the pI profile of FSH is due either to the limited duration of the culture period employed or to the possibility that steroids exert their effect on the pituitary through an indirect mechanism.