Purification of a bioactive FSH-releasing factor (FSHRF).
Before the advent of radioimmunoassay (RIA), FSH-releasing factor (FSHRF) appeared to be separable from LH-releasing hormone (LHRH) by chromatography followed by bioassay for FSH. In this study, we re-examined hypothalamic extracts for the existence of an FSHRF distinct from LHRH, utilizing the Steelman-Pohley bioassay as well as RIA for identification of FSH. Acid extracts of rat hypothalamic fragments were chromatographed on Sephadex G-25. LH- and FSH-releasing activities of each fraction were assessed by bio- and immunoassay of FSH and immunoassay of LH released after incubation with hemipituitaries from adult male rats. The immunoreactive LHRH(IR-LHRH) concentration of each fraction was also measured by RIA. In order to evaluate the FSH-releasing activity of LHRH, three doses of synthetic LHRH were tested and FSH-releasing activity determined by bio- and immunoassay. By RIA, the FSH-releasing activity of each column fraction could be accounted for by IR-LHRH contamination. However, greater FSH-releasing activity than could be predicted by IR-LRH contamination was detected by Steelman-Pohley assay in fractions eluted prior to the LHRH peak in 2 separate fractionations. These fractions from the second fractionation were pooled and eluted from a CMC column with ammonium acetate buffers. Again greater FSH-releasing activity than could be accounted for by IR-LHRH was detected prior to the IR-LHRH peak by Steelman-Pohley assay. These results agree with early work from our laboratory and suggest the presence of a bioactive FSHRF in hypothalamic extracts.
D000818:Animals; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D007987:Gonadotropin-Releasing Hormone / Q000302:isolation & purification*; D007031:Hypothalamus / Q000032:analysis*; D008297:Male; D010903:Pituitary Gland, Anterior / Q000032:analysis; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains
D007987:Gonadotropin-Releasing Hormone