Costoff A
Maturitas. 1985 Nov;7(4):351-65. doi: 10.1016/0378-5122(85)90059-3.
Estradiol-17 beta and estradiol-17 beta-progesterone were administered to aging female rats immediately after castration. Estradiol (1.6 micrograms) alone suppressed the castration hypersecretion of FSH in mature animals to 70% of the castration controls, but in 360-day-old and older animals, the inhibition was less than 10%. There was a decrease in the castration hypersecretion of LH by exogenous estradiol-17 beta with increasing age, but the pattern of suppression was similar in all animals, regardless of age. When a constant dose of estradiol-17 beta of 0.4 micrograms/kg body wt. was administered to castrate rats with varying doses of progesterone, it was shown that after 270 days of age the negative feedback effect of these steroids on FSH secretion was not found. Whereas, when progesterone of varying doses was administered with a constant dose of 0.8 micrograms/kg BW of estradiol-17 beta, it was shown that after 180 days of age the positive feedback effect of these steroids on FSH was absent. After 270 days of age the augmentation of LH secretion by estradiol-17 beta and a middle dose of progesterone was not apparent even though the negative feedback on LH was effective. A defect in positive and negative feedback effects of gonadal steroids on gonadotropin secretion may be causative to age-related changes in the estrous cycle of rats.
在切除卵巢后，立即对老龄雌性大鼠给予17β -雌二醇和17β -雌二醇 -孕酮。单独给予雌二醇（1.6微克）可将成熟动物因去势引起的促卵泡激素（FSH）分泌亢进抑制至去势对照组的70%，但在360日龄及以上的动物中，抑制率不到10%。随着年龄增长，外源性17β -雌二醇对促黄体生成素（LH）因去势引起的分泌亢进有降低作用，但在所有动物中，无论年龄大小，抑制模式相似。当给去势大鼠注射0.4微克/千克体重的恒定剂量17β -雌二醇，并搭配不同剂量的孕酮时，结果显示，270日龄后未发现这些类固醇对FSH分泌的负反馈作用。然而，当给大鼠注射不同剂量的孕酮，并搭配0.8微克/千克体重的恒定剂量17β -雌二醇时，结果显示，180日龄后未发现这些类固醇对FSH的正反馈作用。270日龄后，尽管17β -雌二醇和中等剂量孕酮对LH的负反馈作用有效，但它们对LH分泌的增强作用并不明显。性腺类固醇对促性腺激素分泌的正反馈和负反馈作用缺陷可能是大鼠发情周期年龄相关变化的原因。
