DEVELOPMENT OF A 2-SITE SOLID-PHASE IMMUNOCHEMILUMINESCENT ASSAY FOR MEASUREMENT OF DIMERIC INHIBIN-A IN HUMAN SERUM AND OTHER BIOLOGICAL-FLUIDS

Inhibin is a heterodimeric glycoprotein that inhibits the secretion of follitropin from the pituitary and has been isolated in two distinct forms composed of a common a subunit and either a beta(A) or beta(B) s ubunit. Utilizing paired monoclonal antibodies specific to the alpha a nd beta(A) subunit, we have developed an immunochemiluminescent assay for dimeric inhibin-A. The assay is capable of quantifying free and bo und inhibin-h in human serum and follicular fluid. The limit of detect ion is 10 ng/L. Related proteins exhibit little cross-reactivity or in terference, Recovery is excellent. Whereas samples from men and postme nopausal women are near the detection limit of the assay, inhibin-A is higher in the luteal than the follicular phase of normally cycling wo men, 20-fold higher during in vitro fertilization treatment, and simil ar to 200-fold greater in pregnancy. The assay measures inhibin-a in f ollicular fluid from a variety of other species.