Celis M E
Acta Physiol Pharmacol Latinoam. 1985;35(3):281-90.
The aim of the present study was to determine the effect of alpha-MSH on serum LH in order to obtain some clues about the possible, mechanism by which the peptide modifies gonadotropin secretion. Intact female rats treated with alpha-MSH on diestrus 2 afternoon exhibited an increase in serum LH levels at 18 hr on proestrus and an elevated number of ova per rat the day of estrus when compared with saline-treated controls. Moreover, the peptide administered in chronically ovariectomized (CHR-OVX) rats treated with estradiol benzoate (EB) plus low doses of progesterone (P), increased LH in serum as well as P serum levels when compared with levels in CHR-OVX animals treated with EB plus P and saline solution instead of alpha-MSH. It has been shown that LH release is blocked by OVX and adrenalectomy (ADX) on the afternoon of proestrus; this blockade was reversed by an injection of alpha-MSH at the time of the operation. Measurements of P in ADX-OVX animals treated with alpha-MSH showed that P serum levels were maintained for longer periods of time when compared with the P serum levels of ADX-OVX animals treated with saline. On the other hand, alpha-MSH infused into CHR-OVX rats treated with low doses of EB, which can lower serum LH levels, lowered the serum LH even more, although the serum P levels were increased. Finally alpha-MSH did not affect the serum LH levels in diestrous rats. The present results demonstrated that alpha-MSH influences the release of LH by modifying the release and/or the degradation of P. This P, in turn, modifies LH serum concentrations, having either a stimulatory or inhibiting effect on the release of LH, apparently depending on the time period it remains high in serum.
本研究的目的是确定α-促黑素（α-MSH）对血清促黄体生成素（LH）的影响，以便获得有关该肽调节促性腺激素分泌的可能机制的一些线索。在动情周期第2天下午用α-MSH处理的完整雌性大鼠，与用生理盐水处理的对照组相比，在动情前期18小时时血清LH水平升高，并且在动情期当天每只大鼠的卵子数量增加。此外，与用苯甲酸雌二醇（EB）加低剂量孕酮（P）处理并用生理盐水而非α-MSH处理的慢性卵巢切除（CHR-OVX）大鼠相比，给用EB加P处理的CHR-OVX大鼠施用该肽会增加血清LH以及血清P水平。已经表明，在动情前期下午，卵巢切除（OVX）和肾上腺切除（ADX）会阻断LH释放；在手术时注射α-MSH可逆转这种阻断。对用α-MSH处理的ADX-OVX动物的P测量表明，与用生理盐水处理的ADX-OVX动物的P血清水平相比，P血清水平维持的时间更长。另一方面，向用低剂量EB处理的CHR-OVX大鼠中注入α-MSH，虽然血清P水平升高，但可进一步降低血清LH水平，尽管低剂量EB可降低血清LH水平。最后，α-MSH对动情期大鼠的血清LH水平没有影响。目前的结果表明，α-MSH通过改变P的释放和/或降解来影响LH的释放。反过来，这种P会改变LH的血清浓度，对LH的释放具有刺激或抑制作用，这显然取决于它在血清中保持高水平的时间段。
