Expression of the bovine oestrogen receptor-beta (bER beta) messenger ribonucleic acid (mRNA) during the first ovarian follicular wave and lack of change in the expression of bER beta mRNA of second wave follicles after LH infusion into cows

摘要

In a previous study, the ER beta cDNA protein-coding region was utilised to clone bovine ER beta. The objectives in this study were to examine (1) ER beta mRNA expression in ovarian follicles throughout the bovine first follicular wave, and (2) effect of LH infusion into cows on bER beta mRNA expression during the second follicular wave. In experiment 1, heifers (4-5 per 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 oestrus. In experiment 2, saline or LH was pulsed hourly (computer-controlled syringe pump) into cows (n = 31; 5-6 per treatment) at wave emergence for 2 or 4 days: wave I-saline (W1S), wave 2-saline (W2S), or wave 2-LH (25 mug/h; W2LH). Ovaries were removed on day 2 or day 4 after wave emergence. Follicles, 2-19 mm in size, were dissected, frozen, and stored at -80 degreesC for in situ hybridisation with two bER beta cRNA probes, Expression of bER beta mRNA was localised in granulosa cells of healthy follicles. In experiment 1. bER beta mRNA expression did not change with time points of the wave showing no association of bER beta mRNA expression with follicular selection and dominance. However, bER beta mRNA expression decreased with increase in size of all follicles. Expression of bER beta mRNA was greater in very small follicles (2-4 mm) than in large (greater than or equal to9 mm) follicles. In experiment 2, expression of bER beta mRNA in follicles did not differ either between W1S and W2S or between W2S and W2LH. In summary, bER beta mRNA expression decreased with increasing follicular size. However, neither stage of the wave (selection or dominance), nor pulsatile infusion of LH influenced bER beta mRNA expression.