Journal of Clinical Endocrinology & Metabolism, Vol 67, 438-443, Copyright © 1988 by Endocrine Society

ARTICLES

Comparison of inhibin immunological and in vitro biological activities in human serum

DM Robertson, CG Tsonis, RI McLachlan, DJ Handelsman, R Leask, DT Baird, AS McNeilly, S Hayward, DL Healy and JK Findlay
Department of Anatomy, Monash University, Clayton, Victoria, Australia.

A comparison of serum inhibin levels in men and women was undertaken using a sensitive sheep pituitary cell in vitro bioassay and a newly developed heterologous RIA. The RIA was based on an antiserum raised to bovine 31K inhibin using [125I]31K inhibin as tracer. Bovine inhibin alpha- and beta-subunits, bovine activin-A, transforming growth factor- beta, and Mullerian inhibitory substance did not cross-react in the RIA. In both assays, dilutions of serum gave response lines parallel to that of the partially purified human follicular fluid inhibin preparation used as standard. Negligible levels of both bio (B)- and immuno (I) activities were found in serum from women with premature ovarian failure or castrated men. In ovulation-induced cycles, serum B inhibin levels increased progressively from the early to the late follicular phase and remained at the late follicular phase level during the early and midluteal phases. Serum I inhibin levels also rose during the follicular phase, but declined during the early luteal phase before increasing again in the midluteal phase. As a consequence, inhibin B:I ratios varied during the treatment cycle, with high ratios in early follicular (2.86) and early luteal (2.25) phases and a low ratio in the midluteal phase (1.09). Similar changes in serum B:I ratios also occurred during the midcycle and midluteal phases of normal cycles. The B:I ratio was lower (0.35) in normal men. We conclude that the largely similar pattern of inhibin biological and immunological activities in serum obtained during a variety of physiological conditions support the validity of the RIA procedure, and the B:I ratio of serum inhibin varies during the follicular and luteal phases of the cycle and is low in men. Potential reasons for these changes in B:I ratio include the presence of interfering substances in either the bioassay or the RIA, the presence of inhibin isoforms, and/or modulation of secreted forms by sex steroids.

This article has been cited by other articles:

				M. L. Looper, J. A. Vizcarra, R. P. Wettemann, J. R. Malayer, T. D. Braden, R. D. Geisert, and G. L. Morgan Influence of estradiol, progesterone, and nutrition on concentrations of gonadotropins and GnRH receptors, and abundance of mRNA for GnRH receptors and gonadotropin subunits in pituitary glands of beef cows J Anim Sci, January 1, 2003; 81(1): 269 - 278. [Abstract] [Full Text] [PDF]

				D. M. Robertson, T. Stephenson, E. Pruysers, P. McCloud, A. Tsigos, N. Groome, P. Mamers, and H. G. Burger Characterization of Inhibin Forms and Their Measurement by an Inhibin {alpha}-Subunit ELISA in Serum from Postmenopausal Women with Ovarian Cancer J. Clin. Endocrinol. Metab., February 1, 2002; 87(2): 816 - 824. [Abstract] [Full Text] [PDF]

				T. M. Lovell, P. G. Knight, N. P. Groome, and R. T. Gladwell Changes in Plasma Inhibin A Levels During Sexual Maturation in the Female Chicken and the Effects of Active Immunization Against Inhibin {{alpha}}-Subunit on Reproductive Hormone Profiles and Ovarian Function Biol Reprod, January 1, 2001; 64(1): 188 - 196. [Abstract] [Full Text]

				T. M. Lovell, P. G. Knight, N. P. Groome, and R. T. Gladwell Measurement of Dimeric Inhibins and Effects of Active Immunization Against Inhibin {alpha}-Subunit on Plasma Hormones and Testis Morphology in the Developing Cockerel Biol Reprod, July 1, 2000; 63(1): 213 - 221. [Abstract] [Full Text]

				S. Ramaswamy, G. R. Marshall, A. S. McNeilly, and T. M. Plant Dynamics of the Follicle-Stimulating Hormone (FSH)-Inhibin B Feedback Loop and Its Role in Regulating Spermatogenesis in the Adult Male Rhesus Monkey (Macaca mulatta) as Revealed by Unilateral Orchidectomy Endocrinology, January 1, 2000; 141(1): 18 - 27. [Abstract] [Full Text] [PDF]

				D. M. Robertson, N. Cahir, H. G. Burger, P. Mamers, P. I. McCloud, K. Pettersson, and M. McGuckin Combined Inhibin and CA125 Assays in the Detection of Ovarian Cancer Clin. Chem., May 1, 1999; 45(5): 651 - 658. [Abstract] [Full Text] [PDF]

				R. Hertan, P. G. Farnworth, K. L. Fitzsimmons, and D. M. Robertson Identification of High Affinity Binding Sites for Inhibin on Ovine Pituitary Cells in Culture Endocrinology, January 1, 1999; 140(1): 6 - 12. [Abstract] [Full Text]

				S. Christin-Maitre, C. Rongières-Bertrand, M.-L. Kottler, N. Lahlou, R. Frydman, P. Touraine, and P. Bouchard A Spontaneous and Severe Hyperstimulation of the Ovaries Revealing a Gonadotroph Adenoma J. Clin. Endocrinol. Metab., October 1, 1998; 83(10): 3450 - 3453. [Abstract] [Full Text]

				S. Ramaswamy, C. R. Pohl, A. S. McNeilly, S. J. Winters, and T. M. Plant The Time Course of Follicle-Stimulating Hormone Suppression by Recombinant Human Inhibin A in the Adult Male Rhesus Monkey (Macaca mulatta) Endocrinology, August 1, 1998; 139(8): 3409 - 3415. [Abstract] [Full Text] [PDF]

				T. M. Lovell, R. T. Gladwell, F. J. Cunningham, N. P. Groome, and P. G. Knight Differential Changes in Inhibin A, Activin A, and Total {alpha}-Subunit Levels in Granulosa and Thecal Layers of Developing Preovulatory Follicles in the Chicken Endocrinology, March 1, 1998; 139(3): 1164 - 1171. [Abstract] [Full Text] [PDF]