Episodic LH secretion patterns in the mare during the oestrous cycle
Evans, J.W.; Hughes, J.P.; Neely, D.P.; Stabenfeldt, G.H.; Winger, C.M.
Journal of Reproduction and Fertility. Supplement 1979(27): 143-150
1979
ISSN/ISBN: 0449-3087 PMID: 289783 Document Number: 145774
Jugular blood samples were obtained from 8 mares at 5- and/or 20-min intervals for 2-5 days during various phases of the oestrous cycle, and the plasma LH content was determined. An episodic pattern of LH release was observed in 1 or 3 mares sampled during the ovulatory period. Of the other 2 mares, one had a single secretory period and the other had several periods of fluctuating plasma LH concentration. During dioestrus, episodic secretion was observed in 2 mares sampled 11-13 days before and, in 1 mare, 9 days after ovulation. Episodic secretion was not observed (3 mares) during the 2-5 days before ovulation, but plasma LH concentrations fluctuated by as much as 6 ng/ml during a period of 3-4 h. Daily blood samples were obtained from 10 mares (1-8 oestrous cycles per mare) during which 22 single, 18 double and 2 luteal-phase ovulations occurred. Ovulation during dioestrus was accompanied by small increases in plasma LH (1-4 ng/ml), but many similar increases in LH were not accompanied by ovulation. No significant differences in LH secretory patterns were observed between females with single and multiple ovulations. In 1 mare, 4 ovulations occurred in the presence of a prolonged luteal phase; 3 were accompanied by increased LH concentrations, and the other occurred when the LH concentration was low.