Development of the mechanism regulating the preovulatory surge of luteinizing hormone in sheep.

Endocrinology
D L Foster, F J Karsch

Abstract

Development of the mechanism controlling cyclic LH secretion in the sheep was studied by examining the ability of estradiol to elicit LH surges in lambs at various ages. Silastic capsules containing estradiol were implanted sc for a 96-hour period at 3, 7, 12, 20, and 27 weeks of age. (First spontaneous ovulation occursss between 30 and 50 weeks). Although administration of estradiol failed to elicit a discharge of LH at 3 weeks of age, LH surges of progressively increasing magnitude (36 +/- 15, 73 +/- 28, 107 +/- 19 ng/ml) were elicited by estradiol as the lambs became older (7, 12, 20 weeks). By 27 weeks, the maximal serum LH level attained during the induced surge (123 +/- 29 ng/ml) was similar to that of the estrogen-induced LH surge in anestrous adults (179 +/- 23 ng/ml). Ovulation, however, did not occur in response to the induced LH surges. An additional experiment was performed to determine whether, as in the adult, progesterone can block the estradiol-induced LH discharge in the immature (12-week old) female. A sustained elevation of circulating progesterone to levels characteristic of the mid-luteal phase of the estrous cycle of the adult (3--4 ng/ml), beginning 24 h prior to insertion of the estradiol capsules, block...Continue Reading

Citations

Sep 1, 1991·The British Veterinary Journal·F M Moffor, R G Rodway
Aug 1, 1982·Theriogenology·L G Sheffield, A R Ellicott
Apr 13, 2000·Small Ruminant Research : the Journal of the International Goat Association·J P Greyling
Dec 15, 2010·Proceedings of the National Academy of Sciences of the United States of America·Christian MayerJon E Levine
Aug 1, 1996·Journal of Neuroendocrinology·R I WoodD L Foster
Jan 29, 2011·Reproduction : the Official Journal of the Society for the Study of Fertility·J S RedmondM Amstalden
Feb 14, 2012·Animal Reproduction Science·I ValasiG S Amiridis
Mar 20, 2010·Molecular and Cellular Endocrinology·Jeremy T Smith, Iain J Clarke
Feb 13, 2001·Endocrine Reviews·E Terasawa, D L Fernandez

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