Follicular Dominance in Cattle Is Associated With Divergent Patterns of Ovarian Gene Expression for Insulin-Like Growth Factor (IGF)-I,IGF-II,and IGF Binding Protein-2 in Dominant and Subordinate Follicles |
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| Institution: | 1. Department of Animal Sciences, University of Missouri, Columbia, MO 65211, USA;2. Department of Veterinary Medicine and Surgery, University of Missouri, Columbia, MO 65211, USA;1. Laboratory for Veterinary Physiology and Biochemistry, Gamete Research Centre, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk, Belgium;2. Algemeen Medisch Laboratorium, AML, Emiel Vloorsstraat 9, B-2020 Antwerpen, Belgium;1. Laboratory of Biotechnology and Animal Reproduction, BioRep, Federal University of Santa Maria, Roraima Avenue 1000, 97105-900, Veterinary Hospital, Santa Maria, RS, Brazil;2. Department of Medical Clinic, Faculty of Medicine, Federal University of Santa Maria, Roraima Avenue 1000, 97105-900, Santa Maria, RS, Brazil;2. Vereinigte Informationssysteme Tierhaltung w.V. (VIT), 27283 Verden, Germany;3. Institute of Animal Breeding, Bavarian State Research Centre for Agriculture, 85586 Poing, Germany;1. Departamento de Zootecnia, Faculdade de Ciências Agrárias e Veterinárias, UNESP-Univ Estadual Paulista, Jaboticabal, SP, Brasil;2. Departamento de Zootecnia, Escola de Medicina Veterinária e Zootecnia, Universidade Federal da Bahia, Salvador, BA, Brasil;3. Departamento de Ecologia, Zoologia e Genética, Universidade Federal de Pelotas, Pelotas, RS, Brasil;1. Eutheria Foundation, Cross Plains, Wisconsin, USA;2. Pathobiological Sciences Department, School of Veterinary Medicine, University of Wisconsin–Madison, Madison, Wisconsin, USA |
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| Abstract: | A decrease in insulin-like growth factor (IGF) binding protein (BP) amount occurs within the follicular fluid of dominant ovarian follicles. At the same time, concentrations of follicular fluid IGF-I do not change. The mRNA for IGF-I, IGF-II, IGFBP-2, and IGFBP-3 in dominant and subordinate follicles were measured to determine if changes in IGF or IGFBP gene expression are associated with follicular dominance. Heifers were ovariectomized during a follicular wave, either during early-dominance (emerging dominant follicle, 9 mm diameter) or mid-dominance (established dominant follicle, 14–16 mm diameter). Follicles were classified as either dominant (DF), subordinate (SF), or not-recruited (NRF; small antral follicles). mRNA was localized by in situ hybridization and measured by image analyses. The IGF-I mRNA (granulosa cells) was greatest in DF and increased in DF, SF, and NRF from early- to mid-dominance. Likewise, IGF-II mRNA (theca cells) was greatest in DF compared with SF or NRF. The IGFBP-2 mRNA (granulosa cells), however, was nearly undetectable in DF, whereas adjacent SF expressed abundant IGFBP-2 mRNA. The NRF were not uniform in their IGFBP-2 expression because only 5 of 13 NRF had IGFBP-2 mRNA. The IGFBP-3 mRNA (granulosa cells) was found only in two NRF, suggesting that local synthesis is not a predominant source of follicular fluid IGFBP-3. These data show that changes in gene expression for IGFBP-2 are opposite to those for IGF-I or IGF-II. Increased IGF-I and IGF-II mRNA and decreased IGFBP-2 mRNA within the DF may be one mechanism leading to follicular dominance. The opposite pattern of IGFBP-2 gene expression in SF and some NRF may lead to follicular atresia. |
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