Preprogramming of luteal progestational function by preovulatory luteinizing hormone surge in cycling rats.

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  • 黄体形成ホルモン(LH)の大量放出によるラット発情周期黄体のProgesterone (P)分泌能の調節
  • 黄体形成ホルモン(LH)の大量放出によるラット発情周期黄体のProgesterone(P)分泌能の調節〔英文〕
  • オウタイ ケイセイ ホルモン LH ノ タイリョウ ホウシュツ ニ ヨル ラッ

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Abstract

Effects of hCG and anti-ovine LH serum (aLH) administration at the time of the preovulatory LH surge on both luteal progesterone secretion and subsequent vaginal cyclicity were investigated. In control 4-day cycling rats, blood progesterone (P) increased from 0400 hr on estrus (E) to 2300 hr on metestrus (M), then declined to a low level by 1800 hr on diestrus (D). A single iv injection of hCG (1.25 or 5 IU) at 1900 hr on proestrus (PE) suppressed the metestrous rise in blood P levels and prolonged the diestrous phase, in a dose-dependent manner, without affecting the numbers of oocytes released at ovulation. Attenuation of the LH surge by a single iv injection of aLH (0.3ml) at 1900 hr on day PE also had a similar effect. Injections of 0.1 ml aLH (ip, every 11-12 hr) from 0800 hr, but not from 0000 hr, on day E in the rats pretreated with hCG on day PE elevated blood P levels, from days E through D, above the values measured in control animals. The lutein cells from rats treated with hCG on day PE were found, by electron microscopy, to be in the process of structural luteolysis at as early as 2300 hr on day M, whereas luteinization appeared still insufficient in the lutein cells from the LH surge-attenuated animals even at this stage. These results confirm a previous finding that tonic levels of LH secreted during the postovulatory period cause luteolysis of a new crop of corpora lutea, and suggest that the magnitude of the ovulatory LH surge preprogrammes luteal function not only by potentiating luteal ability to secrete P but also by determinig the timing of the expression of luteal sensitivity to the suppressing effect of LH. The prolonged diestrous phase accompanied by suppressed luteal function observed in the animals treated with hCG alone on day PE suggests that the magnitude of the LH surge is probably involved also in regulation of the subsequent follicular growth and estrogen secretion.

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