HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 70/5/1374    most recent biolreprod.103.026195v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal My Folders Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ginther, O.J. Articles by Beg, M.A. Search for Related Content PubMed PubMed Citation Articles by Ginther, O.J. Articles by Beg, M.A. Agricola Articles by Ginther, O.J. Articles by Beg, M.A.

Critical Role of Insulin-Like Growth Factor System in Follicle Selection and Dominance in Mares¹

Eutheria Foundation, Cross Plains, Wisconsin 53528

The role of the insulin-like growth factor (IGF) system in the deviation in growth rates among follicles (follicle selection) was studied in mares using an IGF binding protein (BP) to reduce the follicular-fluid concentrations of IGFs. The future dominant follicle (F1) was treated by intrafollicular injection at the expected beginning of deviation (F1 20 mm; Day 0). The experimental groups were control (no injection, n = 8), vehicle (injection of vehicle; n = 6), and BP (injection of 250 µg of recombinant human IGFBP-3; n = 6). A sample of follicular fluid was taken from F1 on Day 1 in all groups. Compared with the control group, IGFBP-3 reduced (P < 0.05) the follicular-fluid concentration of free IGF-1 by 90%; lowered (P < 0.05) the concentrations of estradiol, activin-A, inhibin-A, and vascular endothelial growth factor; and increased (P < 0.05) the concentration of androstenedione. The diameter of F1 decreased and the diameter of F2 increased after Day 0 in the BP group, compared with the control and vehicle groups. A greater (P < 0.05) increase in circulating concentrations of FSH between Days 0 and 1 occurred in the BP group than in the other groups and accounted for the increased growth of F2. Dominance and ovulation from F1 occurred from fewer (P < 0.03) mares in the BP group (1 of 6) than from the control and vehicle groups combined (11 of 14); the remaining mares in the BP group ovulated from F2. Results indicated that the IGF system has a critical intrafollicular role in the differential changes in concentrations of follicular-fluid factors between the future dominant and subordinate follicles, leading to the development of follicle dominance (selection) and ovulation in mares.

¹ Supported by the Eutheria Foundation, Cross Plains, WI. Project P4-OG- 03. E.L. and M.O. Gastal are on leave from the Departments of Veterinary and Animal Science, respectively, Federal University of Viçosa, Viçosa, Brazil.

² Correspondence: O.J. Ginther, Animal Health and Biomedical Sciences, 1656 Linden Drive, University of Wisconsin, Madison WI 53706. FAX: 608 262 7420; ginther{at}svm.vetmed.wisc.edu

This article has been cited by other articles:

				L K Doyle, C O Hogg, E D Watson, and F X Donadeu Seasonal effects on the response of ovarian follicles to IGF1 in mares Reproduction, November 1, 2008; 136(5): 589 - 598. [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]

				O J Ginther, E L Gastal, M O Gastal, and M A Beg In vivo effects of pregnancy-associated plasma protein-A, activin-A and vascular endothelial growth factor on other follicular-fluid factors during follicle deviation in mares Reproduction, April 1, 2005; 129(4): 489 - 496. [Abstract] [Full Text] [PDF]

				T.J. Acosta, E.L. Gastal, M.O. Gastal, M.A. Beg, and O.J. Ginther Differential Blood Flow Changes Between the Future Dominant and Subordinate Follicles Precede Diameter Changes During Follicle Selection in Mares Biol Reprod, August 1, 2004; 71(2): 502 - 507. [Abstract] [Full Text] [PDF]

				T.J. Acosta, M.A. Beg, and O.J. Ginther Aberrant Blood Flow Area and Plasma Gonadotropin Concentrations During the Development of Dominant-Sized Transitional Anovulatory Follicles in Mares Biol Reprod, August 1, 2004; 71(2): 637 - 642. [Abstract] [Full Text] [PDF]