Submitted to: Biology of Reproduction Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: April 29, 2005
Publication Date: July 20, 2005
Citation: Echternkamp, S.E., Cushman, R.A., Christenson, R. 2005. Increased mRNA expression for FSH receptor in small antral follicles in the ovarian cortex of twin-producing cattle [abstract]. Biology of Reproduction. (Supplement):93. (Abstract #53) Technical Abstract: Cattle selected for the production of twin ovulations and births have enhanced preantral and antral follicular development and increased responsiveness to low dosages of FSH. However, differences in FSH secretion have not been found between selected (Twinner) and unselected (non-Twinner) cattle; Twinner females have greater IGF-I in blood and follicular fluid. The objective of this study was to compare mRNA expression for FSH receptor in small(< 5 mm) antral follicles from Twinner (n=12) and non-Twinner (n=14) cattle. Ovaries were collected from cyclic (d 5 or 6) cows at slaughter and pieces of cortical tissue were fixed in 4% formaldehyde, dehydrated in alcohol and embedded in paraffin. FSH receptor mRNA expression was evaluated by in situ hybridization analysis using 35SUTP-labelled cRNA antisense and sense probes synthesized from a 637-bp cDNA of bovine FSH receptor (Xu et al., 1995; Biol. Reprod. 53:951-957). Slides were exposed to Kodak NTB-2 emulsion for 4 wk. FSH receptor mRNA was localized within the granulosa cells of both preantral (especially, secondary) and antral follicles. Silver grain density was quantified in four areas within each antral follicle having an intact granulosa (range of 2 to 7 follicles/cow) using the Bioquant image analysis system. Antisense minus sense density measurements were averaged for the four replicates/follicle and the specific expression data were analyzed for a genetic effect using SAS Proc Mixed for repeated measurements. Expression of mRNA for FSH receptor was greater in the granulosa of small antral follicles from Twinner compared with non-Twinner cows (11.92±1.21 vs. 7.61±1.01% specific grains; P < 0.05). FSH receptor mRNA did not vary with follicle diameter (r = -0.12; P > 0.1). It is speculated that the increased antral follicular development in the Twinner cattle population is associated with greater numbers of FSH receptors, which may be associated with the increased IGF-I concentrations in blood and follicular fluid of Twinner females.