title: Human follicular fluid contains a follicle-stimulating hormone (FSH) receptor binding inhibitor which has FSH agonist activity, is immunologically similar to FSH, but can be distinguished from FSH.
abstract: We have previously reported the presence in human follicular fluid (hFF) of a high (greater than 5000) mol wt FSH receptor binding inhibitor (FSH-BI). This hFF FSH-BI was further purified by removal of material insoluble in acidified acetone (pH 4.1) but soluble in diethyl ether (pH 10.5), followed by molecular sieving through Sephacryl S-100. FSH-BI activity eluted from S-100 with an elution volume similar to that of hFSH, but could be distinguished from hFSH on the basis of a differential sensitivity to acid inactivation. Human FSH was inactivated in acetone at pH 4.1 (1 h, 25 C), whereas hFF FSH-BI retained activity under these conditions. Human FF FSH-BI also demonstrated FSH-like agonist activity, defined as the ability to stimulate basal levels of estradiol synthesis in cultured rat Sertoli cells. Human FSH-BI strongly cross-reacted to a commercially available monoclonal antibody used to measure serum hFSH. Indeed, recovery of FSH immunologic activity was significantly greater (134-fold on a mass basis) after partial purification, indicating that antibody recognition sites were apparently masked in unfractionated hFF. In summary, large mol wt hFSH-BI has been partially purified from hFF and found to be similar in size to pituitary hFSH and to have FSH-like agonist activity in vitro. Although distinguishable from pituitary hFSH on the basis of stability to acid, hFSH-BI appears immunologically related to pituitary hFSH so that measurements of hFSH levels in hFF using immunologic techniques should be interpreted with caution.
authors.affiliation: Department of Biochemistry, Albany Medical College, New York 12208.
authors.forename: D W
authors.initials: DW
authors.lastname: Lee
authors.forename: W J
authors.initials: WJ
authors.lastname: Butler
authors.forename: P M
authors.initials: PM
authors.lastname: Horvath
authors.forename: R M
authors.initials: RM
authors.lastname: Shelden
authors.forename: L E
authors.initials: LE
authors.lastname: Reichert
mesh_terms: D000096:Acetone / Q000494:pharmacology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D002352:Carrier Proteins; D002478:Cells, Cultured; D002850:Chromatography, Gel; D003429:Cross Reactions / Q000276:immunology; D004958:Estradiol / Q000096:biosynthesis; D005260:Female; D005640:Follicle Stimulating Hormone / Q000037:antagonists & inhibitors* / Q000276:immunology / Q000502:physiology; D015571:Follicular Fluid / Q000737:chemistry* / Q000502:physiology; D006020:Glycopeptides / Q000032:analysis* / Q000276:immunology / Q000502:physiology; D006801:Humans; D008297:Male; D011869:Radioligand Assay; D051381:Rats; D011919:Rats, Inbred Strains; D012708:Sertoli Cells / Q000187:drug effects / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; C484018:FSH-BI protein, human; D006020:Glycopeptides; C063151:follicle-stimulating hormone-suppressing protein, rat; D000096:Acetone; D004958:Estradiol; D005640:Follicle Stimulating Hormone