Biology of Reproduction, Vol 50, 1265-1276, Copyright © 1994 by Society for the Study of Reproduction

ARTICLES

Alterations in amounts of different forms of inhibin during follicular atresia

JL Ireland, TE Good, PG Knight and JJ Ireland
Department of Animal Science, East Lansing, Michigan 48824.

An inhibin immunoblot procedure was validated for measurement of inhibins (alpha beta) and inhibin alpha subunits in bovine follicular fluid (bFF) from individual follicles. Bovine FF was removed from nonovulatory follicles (> or = 6 mm in diameter) of cows during early diestrus. Ratio of progesterone (P) to estradiol (E) concentrations was used to classify follicles into three different stages of differentiation and atresia: estrogen-active (EA; PE ratio < 1), atretic (PE = 1-100), and highly atretic (PE = > 100). Bovine inhibin (bINH) was analyzed by an immunoblot procedure, an RIA that cross- reacts with inhibin alpha beta dimers and alpha subunits, and a two- site alpha beta dimer-specific immunoradiometric assay (IRMA). Immunoblots consistently detected 9 different bINH forms in bFF of each follicle. The average molecular mass for the bINH forms ranged from 29 to > 160 kDa, which was similar to those for purified bINH and bINH alpha subunits. The predominant bINH forms were > or = 122 kDa. Amounts of most bINH forms decreased several fold during atresia of EA follicles. However, the 34-kDa form increased 1.9-fold. To examine whether amounts of each bINH form varied independently during atresia, proportion of total bINH immunoblot activity represented by each bINH form was statistically analyzed. The results indicated that the proportion of total immunoblot activity for the 34-, 68-, and > 160-kDa bINH forms increased during atresia, whereas proportions for the 48-, 49-, and 122-kDa forms decreased. Alterations in amounts of most bINH forms were positively correlated with intrafollicular concentrations of E and negatively correlated with P. In contrast, the 34-kDa bINH form was negatively correlated with E, but positively correlated with P. Total bINH concentrations determined by RIA decreased 3-fold during atresia. However, amounts of most forms of bINH, except the 29-kDa form (r = 0.72), were relatively weakly correlated (r < 0.41) or not correlated with the RIA results. In contrast to RIA results, concentration of dimeric forms of bINH measured by IRMA increased 2.5- fold during atresia, but only the 34-kDa form of bINH was correlated (r = 0.77) with IRMA results.(ABSTRACT TRUNCATED AT 400 WORDS)

This article has been cited by other articles:

				J Buratini Jr., M.G.L Pinto, A.C Castilho, R.L Amorim, I.C Giometti, V.M Portela, E.S Nicola, and C.A Price Expression and Function of Fibroblast Growth Factor 10 and Its Receptor, Fibroblast Growth Factor Receptor 2B, in Bovine Follicles Biol Reprod, October 1, 2007; 77(4): 743 - 750. [Abstract] [Full Text] [PDF]

				M A Beg and O J Ginther Follicle selection in cattle and horses: role of intrafollicular factors. Reproduction, September 1, 2006; 132(3): 365 - 377. [Abstract] [Full Text] [PDF]

				F. Jimenez-Krassel, M. E. Winn, D. Burns, J. L. H. Ireland, and J. J. Ireland Evidence for a Negative Intrafollicular Role for Inhibin in Regulation of Estradiol Production by Granulosa Cells Endocrinology, May 1, 2003; 144(5): 1876 - 1886. [Abstract] [Full Text] [PDF]

				H. Kaneko, J. Noguchi, K. Kikuchi, J. Todoroki, and Y. Hasegawa Alterations in Peripheral Concentrations of Inhibin A in Cattle Studied Using a Time-Resolved Immunofluorometric Assay: Relationship with Estradiol and Follicle-Stimulating Hormone in Various Reproductive Conditions Biol Reprod, July 1, 2002; 67(1): 38 - 45. [Abstract] [Full Text] [PDF]

				E. C.L. Bleach, R. G. Glencross, S. A. Feist, N. P. Groome, and P. G. Knight Plasma Inhibin A in Heifers: Relationship with Follicle Dynamics, Gonadotropins, and Steroids During the Estrous Cycle and after Treatment with Bovine Follicular Fluid Biol Reprod, March 1, 2001; 64(3): 743 - 752. [Abstract] [Full Text]

				E.J. Austin, M. Mihm, A.C.O. Evans, P.G. Knight, J.L.H. Ireland, J.J. Ireland, and J.F. Roche Alterations in Intrafollicular Regulatory Factors and Apoptosis During Selection of Follicles in the First Follicular Wave of the Bovine Estrous Cycle Biol Reprod, March 1, 2001; 64(3): 839 - 848. [Abstract] [Full Text]

				M. Mihm, E.J. Austin, T.E.M. Good, J.L.H. Ireland, P.G. Knight, J.F. Roche, and a. J.J. Ireland Identification of Potential Intrafollicular Factors Involved in Selection of Dominant Follicles in Heifers Biol Reprod, September 1, 2000; 63(3): 811 - 819. [Abstract] [Full Text]

				C. Cariou-Guennoc, J.C. Poirier, B. Calas, A. Locatelli, J.L. Dacheux, and M.R. Blanc Evidence That Luteinizing Hormone-Releasing Hormone Statin from Ovine Rete Testis Fluid Is Immunologically Related to {alpha}C Inhibin Biol Reprod, June 1, 2000; 62(6): 1551 - 1563. [Abstract] [Full Text]