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KMID : 1094020140310010025
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Journal of Veterinary Clinics
2014 Volume.31 No. 1 p.25 ~ p.30
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Effects of Priming Progesterone on the LH Surge Expressions in Ovariectomized Shiba Goats
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Kim Seung-Joon
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Abstract
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This study tested the hypothesis that the priming effects of progesterone on the timing of the LH surgeinduced by exogenous estradiol are more potentiated the negative feedback actions of progesterone on LH secretionby the existence of estradiol. In previous studies, the time interval from estradiol infusion until the peak of LH surgewas gradually and significantly extended by the different levels of progesterone treated before estradiol infusions. Longtermovariectomized Shiba goats that had received implants of estradiol capsules (Day 0) and three different progesteronesilastic packet inducing follicular, subluteal and luteal levels of progesterone were divided into three groups such asnon-P, low-P and high-P group. Blood samples were collected daily throughout the experiment for the analysis ofgonadal steroid hormone levels. On Day 7, all devices of progesterone and estradiol packets were removed but estradiolcapsules were maintained during the experiment, and blood samples were collected at 1 hr interval for 12 h from thetime of progesterone removals to determine peripheral changes of estradiol and progesterone concentration. Then allanimals were infused estradiol on the Day 7 after 13 h from the removals of progesterone devices with a peristalticpump into jugular vein at a rate of 3-6 μg/h for 36 h. For analysis of peripheral LH and estradiol concentration, bloodsamples were collected via another jugular vein at 2 h intervals for 52 h (from 4 h before the start of estradiol infusionto 48 h after the start of estradiol infusion). In all animals of the three groups treated with estradiol infusion, an LHsurge was expressed but the peak time of LH surge was different. This time interval was not extended by the differentlevels of progesterone treated before estradiol infusions and the difference was not significant during this intervalbetween the Low P and the High P groups. Progesterone pretreatment may contribute to regulating the neural systemthat is responded by estradiol, and estradiol existence potentiates the negative feedback effect of progesterone on GnRH/LH surge-generating system.
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KEYWORD
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estradiol, progesterone, Luteinizing hormone surge, ovariectomized goat
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