title: Radioimmunoassay of inhibin based on synthetic human inhibin alpha-chain peptide.
abstract: Polyclonal rabbit antisera were produced against cyclic human inhibin [(Cys6, Tyr7) alpha-(6-30)NH2] peptide, covalently conjugated to bovine serum albumin. The tyrosine residue introduced at position 7 facilitated the oxidative incorporation of radiolabel (125I) to yield a tracer with specific activity of 73.9 Ci/g. These reagents were used to develop a homologous equilibrium radioimmunoassay for human inhibin, with polyethylene glycol, 200 g/L, serving as the separation phase. At a detection limit of 2 micrograms/L (n = 7), immunoactive inhibin was detectable in human pre-ovulatory follicular fluid (128 micrograms/L), seminal plasma (2374 micrograms/L), amniotic fluid (66 micrograms/L), and placental extract (347 micrograms/L). We also demonstrated inhibin immunoreactivity in biological fluids from other mammalian species: macaque, chimpanzee, porcine, and bovine, but not rodent (guinea pig). Although the antisera were raised against a nonbioactive inhibin peptide, immunoglobulins fractionated on Protein A-Sepharose neutralized the bioactivity of human ovarian inhibin. Further characterization of inhibin immuno- and bioactivity was undertaken with immobilized heparin, divalent metal cations, and dye ligands. Only heparin-Sepharose distinguished between immuno- and bioactive inhibin.
authors.affiliation: Department of Obstetrics and Gynaecology, Royal North Shore Hospital, St. Leonards, NSW, Australia.
authors.forename: M J
authors.initials: MJ
authors.lastname: Sinosich
authors.forename: S
authors.initials: S
authors.lastname: Sieg
authors.forename: A
authors.initials: A
authors.lastname: Zakher
authors.forename: N
authors.initials: N
authors.lastname: Ling
authors.forename: D M
authors.initials: DM
authors.lastname: Saunders
authors.forename: Z
authors.initials: Z
authors.lastname: Rosenwaks
authors.forename: G D
authors.initials: GD
authors.lastname: Hodgen
mesh_terms: D000653:Amniotic Fluid / Q000737:chemistry; D000818:Animals; D000941:Antigens / Q000276:immunology; D001681:Biological Assay; D002845:Chromatography; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D015571:Follicular Fluid / Q000737:chemistry; D006801:Humans; D007106:Immune Sera; D007265:Inhibins / Q000032:analysis* / Q000276:immunology / Q000494:pharmacology; D007457:Iodine Radioisotopes; D008297:Male; D010446:Peptide Fragments / Q000276:immunology; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism; D010920:Placenta / Q000737:chemistry; D011863:Radioimmunoassay / Q000379:methods*; D051381:Rats; D012661:Semen / Q000737:chemistry; D012710:Serum Albumin, Bovine / Q000276:immunology
chemical_list: D000941:Antigens; D007106:Immune Sera; D007457:Iodine Radioisotopes; D010446:Peptide Fragments; D012710:Serum Albumin, Bovine; D007265:Inhibins; D005640:Follicle Stimulating Hormone