Submitted to: Biology of Reproduction Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: April 23, 1997
Publication Date: N/A
Patterns of pituitary gene expression for GnRH receptor and gonadotropin subunits during the bovine preovulatory period in normal cows (NORM; n=17) and cows selected for natural twin births (TWIN; n=18) were evaluated. Anterior pituitary glands were collected 0, 24, 48 or 72 h following treatment with 30 mg PGF2alpha (PG) on Day 17 or 18 of the estrous cycle to oinduce luteolysis (n=5-7 per time point). Polyadenylated RNA was prepared from pituitary tissues, its integrity was verified by Northern blot analysis, and steady-state amounts of mRNA encoding GnRH receptor, FSHbeta subunit, LHbeta subunit, and alpha subunit were quantified by slot blot analysis. In NORM cows, amount of GnRH receptor mRNA tended to be elevated (p<.10) at 24 h and was increased twofold (p<.02) at 48 h after treatment with PG but at 72 h, amounts were similar to those at 0 h. At 24, 48, and 72 h following induction of luteolysis, amounts of FSHbeta subunit mRNA in NORM cows were decreased (p<.01) to 31.3 +/- 2.1% of the amount in cows at 0 h. In contrast, amounts of mRNA encoding GnRH receptor and FSHbeta subunit in TWIN cows did not change following treatment with PG (p>.25). No significant change in amounts of mRNA encoding LHbeta or alpha subunits was observed in either NORM or TWIN cows after treatment with PG. Comparison between NORM and TWIN cows revealed that amounts of alpha subunit mRNA were greater in TWIN cows (p<.01). These results indicate that amounts of GnRH receptor mRNA increase and amounts of FSHbeta mRNA decrease during the bovine preovulatory period. However, similar patterns of gene expression were not observed in cows selected for natural twin births. These findings provide additional insight into possible mechanisms underlying ovarian follicular development in cattle selected for natural twin births.