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RESEARCH ARTICLE
Contents Vol 22(7)

Positive effect of FSH but not LH on early development of the dominant follicle in mares

C. M. Checura A B , M. A. Beg B , J. J. Parrish C and O. J. Ginther A B D
+ Author Affiliations
- Author Affiliations

A Eutheria Foundation, Cross Plains, WI 53528, USA.

B Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA.

C Department of Animal Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA.

D Corresponding author. Email: ginther@vetmed.wisc.edu

Reproduction, Fertility and Development 22(7) 1092-1099 https://doi.org/10.1071/RD09275
Submitted: 10 November 2009  Accepted: 19 February 2010   Published: 20 August 2010

Abstract

The effects of FSH, LH or both on follicular growth and intrafollicular free insulin-like growth factor (IGF)-1 and oestradiol were investigated in mares after the beginning of deviation (largest follicle ≥ 20 mm; Hour 0). A single treatment with a gonadotropin-releasing hormone antagonist (acyline) was given at Hour 3 to suppress the concentrations of FSH and LH. Five groups (n = 5 mares per group) were evaluated in the present study: (1) control; (2) acyline treated; (3) acyline + recombinant equine (re) FSH treated; (4) acyline + reLH treated; and (5) combined acyline + reFSH + reLH treated. Beginning at Hour 3, reFSH and reLH were given at 6-h intervals in eight decreasing or increasing doses, respectively. The reFSH and reLH prevented the acyline-induced decreases in FSH and LH, respectively. Diameters and concentrations of intrafollicular free IGF-1 and oestradiol of the two largest follicles at Hour 48 did not differ significantly between the control and acyline + FSH groups, but were reduced (P < 0.05) similarly in the acyline and acyline + LH groups. The combination of reFSH and reLH was no more effective than reFSH alone. The results demonstrate a role for FSH but not LH in the growth of the largest follicle and intrafollicular concentrations of free IGF-1 and oestradiol during the 48 h after the beginning of deviation in mares.

Additional keywords: follicular deviation, follicular selection, GnRH antagonist, intrafollicular IGF-1, intrafollicular oestradiol.


Acknowledgements

This work was supported by the Eutheria Foundation (projects P3-CC-07, P4-CC-07, P1-CC-08 and P2-CC-08). The authors thank Miller Palhao, Bernardo Rodrigues and Md Almamun for technical assistance, Richard Blye (National Institute of Child Health and Human Development, National Institutes of Health) for acyline and Mark Colgin (AspenBio Pharma) for the recombinant gonadotropins.


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