EFFECTS OF OVARIECTOMY AND FECB(B) GENOTYPE ON THE MEDIAN CHARGE AND CIRCULATING HALF-LIFE OF PITUITARY FSH ISOFORMS OF EWES

This study investigated the effects of short-term (20 days) ovariectom y, the effects of FSH assay (radioimmunoassay, receptor assay or in vi tro bioassay) and of FecB(B) genotype on the characteristics of pituit ary FSH from Booroola ewes. Pituitary extracts were obtained from ovar iectomized homozygous carriers (BB) and non-carriers (++, n = 8 per ge notype) and ovary-intact controls (n = 4 per genotype). The extracts ( n = 4 per genotype per treatment) were subjected to agarose suspension electrophoresis and the eluates were assayed by the three FSH methods . There were significant effects of ovariectomy (P < 0.01) and assay s ystem (P < 0.05) but not of genotype on the median charge of FSH isofo rms. The mean +/- SEM migration rates for FSH in intact and ovariectom ized ewes were 0.469 +/- 0.006 and 0.439 +/- 0.006 albumin mobility un its, respectively (P < 0.01), indicating a shift to more basic isoform s after short-term ovariectomy. When the pituitary extracts were subje cted to anion-exchange HPLC, there was a significant (P < 0.01) shift to more basic isoforms in the ovariectomized ewes as shown using agaro se electrophoresis, and no gene effects were noted. When the pituitary extracts (n = 4-8 per group) were injected into mature female mice, t here were no significant effects of ovariectomy or genotype on the cir culating half-lifes of the pituitary FSK isoforms. These results indic ate that after short-term ovariectomy, the increase in plasma FSH conc entrations is accompanied by a shift in the median charge of pituitary FSH isoforms without any observable change in their metabolic clearan ce rates. Moreover, the FecB(B) gene has little effect on the median c harge or half-life of pituitary FSH.