Abstract: 52

EXPRESSION OF BOVINE ESTROGEN RECEPTOR- (bER) mRNA THROUGHOUT THE FIRST FOLLICULAR WAVE IN THE OVARY AND EFFECT OF LH INFUSION ON bER mRNA EXPRESSION OF SECOND WAVE FOLLICLES.

Mohan Manikkam^{1 *}, Bagna Bao¹ , Cheryl S Rosenfeld^{1 *}, Xiaohui Yuan² , Brent E Salfen^{1 *}, Michele D Calder¹ , Robert S Youngquist^{3 *}, Duane H Keisler^{1 *}, Dennis B Lubahn² , Henry A Garverick^{1 *}
Department of Animal Sciences, University of Missouri, Columbia, MO ¹
Department of Biochemistry & Child Health, University of Missouri, Columbia, MO ²
Department of Veterinary Medicine & Surgery, University of Missouri, Columbia, MO ³

Utilizing the ER cDNA protein-coding region we have previously cloned the bovine ER. Our objectives were to examine 1) bER mRNA expression in follicles throughout the first wave, and 2) effect of LH infusion into cows on bER mRNA expression during the second wave. In Experiment 1, heifers (4-5/time point) were ovariectomized at 12, 24, 36, 48, 60, 72, 84, 96, 144 or 216 h after emergence of the first follicular wave after estrus. In Experiment 2, Saline or LH was pulsed hourly (computer-controlled syringe pump) into cows (n=31; 5-6/treatment) at wave emergence for 2 or 4 days: Wave 1, Saline (W1S); Wave 2, Saline (W2S); or Wave 2, LH (25 µg/h; W2LH). Ovaries were removed on day 2 or 4 after wave emergence. Follicles were dissected, frozen and stored at -80°C for in situ hybridization. Expression of bER mRNA was localized in granulosa cells of healthy follicles. In Experiment 1, bER mRNA expression did not change with time points of the wave (r = -0.06; p = 0.47). However, bER mRNA expression decreased with type of follicle (very small [<4 mm], small [4 mm], growing [5-8 mm] and large [=9 mm]; linear regression coefficient, b= -1.91 ±0.86; p=0.02). Expression of bER in very small follicles was greater than in large follicles (p<0.05). In Experiment 2, expression of bER mRNA in follicles did not differ either between W1S and W2S (p = 0.70), between W2S and W2LH (p = 0.28) or between day 2 and day 4 of the follicular wave (p = 0.66). In summary, bER mRNA expression decreases with increasing follicular size. However, neither stage of the wave, nor pulsatile infusion of LH influences bER mRNA expression.

    This abstract is being presented on Sunday, August 1 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.