LONG-TERM NEGATIVE FEEDBACK EFFECTS OF ESTROGEN AND PROGESTERONE ON THE PITUITARY-GLAND OF THE LONG-TERM OVARIECTOMIZED EWE
LONG-TERM NEGATIVE FEEDBACK EFFECTS OF ESTROGEN AND PROGESTERONE ON THE PITUITARY-GLAND OF THE LONG-TERM OVARIECTOMIZED EWE
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DOI：
10.1677/joe.0.1200207
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发表时间：
1989-02-01
影响因子：
4
通讯作者：
NETT, TM
中科院分区：
文献类型：
--
作者：
CLARKE, IJ;CUMMINS, JT;NETT, TM
在切除卵巢的下丘脑-垂体分离母羊中，研究了生理剂量的雌二醇或雌二醇+孕酮长期治疗对血浆促性腺激素水平和垂体LH和促性腺激素释放激素（GnRH）受体含量的影响，每2 h（i. v.）给予250 ng GnRH脉冲。初步实验表明，3 cm长的硅橡胶植入物（s.c.）降低长期（> 6个月）卵巢切除母羊LH脉冲频率和脉冲幅度。在切除卵巢-下丘脑-垂体分离的母羊中进行了3周以上的主要实验，这些母羊在垂体手术后接受了1周的脉冲式GnRH替代。第1组（n = 5）在整个研究期间仅接受GnRH脉冲。第2组（n = 6）在第2周接受雌二醇治疗，第3周接受雌二醇+孕酮治疗，第3组（n = 6）逆转类固醇治疗。雌二醇降低（P < 0.05）平均（. ±. S.E.M.）第2组中脉冲中LH的幅度（从8.2 ±. 1.6至5.0 .+-。0.5μ g/l）和组3（从11.6 ±. 1.2至9.3 .+-。1.0μ g/l;）在第2组中观察到孕酮的附加作用，但在第3组中没有观察到。LH脉冲的幅度在对照母羊中没有变化。血浆FSH浓度降低约50%的雌二醇治疗，没有额外的影响孕酮。类固醇治疗对垂体LH含量或垂体GnRH受体水平无影响。我们的结论是，长期的雌二醇治疗，有或没有孕酮，降低血浆LH脉冲幅度的直接垂体效应，但这种影响的幅度小于在短期卵巢切除母羊的GnRH分泌在早期的研究中观察到的。血浆LH脉冲幅度的降低不是由于这些类固醇对GnRH受体数量的直接垂体效应。
The effects of long-term treatment with physiological doses of oestradiol or oestradiol plus progesterone on plasma gonadotrophin levels and pituitary content of LH and gonadotrophin-releasing hormone (GnRH) receptors were studied in ovariectomized-hypothalamo-pituitary disconnected ewes given 250 ng pulses of GnRH every 2 h (i.v.). A pilot experiment showed that 3 cm long Silastic implants (s.c.) reduced both LH pulse frequency and pulse amplitude in long-term (> 6 months) ovariectomized ewes. The main experiment was conducted over 3 weeks in ovariectomized-hypothalamo-pituitary disconnected ewes that had received pulsatile GnRH replacement for 1 week after pituitary surgery. Group 1 (n = 5) received GnRH pulses alone throughout the study. Group 2 (n = 6) received oestradiol in week 2 and oestradiol plus progesterone in week 3 and in group 3 (n = 6) the steroid treatments were reversed. Oestradiol reduced (P < 0.05) the mean (.+-. S.E.M.) amplitude of LH in pulses in group 2 (from 8.2 .+-. 1.6 to 5.0 .+-. 0.5 .mu.g/l) and group 3 (from 11.6 .+-. 1.2 to 9.3 .+-. 1.0 .mu.g/l;) an additional effect of progesterone was seen in group 2 but not group 3. The amplitudes of the LH pulses did not change in the control ewes. Plasma concentrations of FSH were reduced by approximately 50% by the oestradiol treatments with no additional effects of progesterone. There was no effect of steroidal treatment on pituitary content of LH or pituitary levels of GnRH receptors. We conclude that long-term oestradiol treatment, with or without progesterone, reduces plasma amplitudes of LH pulses by a direct pituitary effect, but the magnitude of this effect was less than that observed on GnRH secretion in short-term ovariectomized ewes in an earlier study. The reduction in plasma LH pulse amplitude is not due to a direct pituitary effect of these steroids on GnRH receptor number.