Gröneveld D, Balm P H, Wendelaar Bonga S E
Department of Animal Physiology, Faculty of Science, University of Nijmegen, The Netherlands.
Peptides. 1995;16(5):945-9. doi: 10.1016/0196-9781(95)00063-p.
The effect of melanin-concentrating hormone (MCH) on the release of alpha-melanocyte stimulating hormone (alpha-MSH) from the tilapia pituitary gland was studied in vitro. In a superfusion set up, 10 nM to 1 microM synthetic salmon MCH caused a concentration-dependent inhibition of alpha-MSH release from tilapia neurointermediate lobes (NILs). Immunoneutralization of MCH in tilapia NILs further indicated that endogenous MCH has an inhibitory effect on the melanotropes. The release of monoacetylated alpha-MSH release was more strongly inhibited by MCH than that of des-, and diacetylated alpha-MSH, indicating that MCH modulates the secretory signal of the melanotropes in a quantitative and qualitative manner. A high concentration of MCH (10 microM) substantially increased the release of alpha-MSH. Further evidence in support of a stimulatory action of high concentrations of MCH was provided by the observation that the MCH analogue MCH(2-17) at 10 and 35 microM enhanced alpha-MSH release as well. Therefore, we conclude that the response of pituitary melanotropes to MCH is biphasic, as was reported previously for the effects of MCH on other targets in fish and mammals. Under physiological conditions the inhibitory action of MCH on fish melanotropes most likely dominates.
在体外研究了黑色素浓缩激素（MCH）对罗非鱼脑垂体中α-黑素细胞刺激素（α-MSH）释放的影响。在一个灌流装置中，10 nM至1 μM的合成鲑鱼MCH对罗非鱼神经中间叶（NILs）中α-MSH的释放产生浓度依赖性抑制。对罗非鱼NILs中的MCH进行免疫中和进一步表明，内源性MCH对促黑素细胞有抑制作用。与去乙酰化和双乙酰化的α-MSH相比，单乙酰化α-MSH的释放受到MCH的抑制作用更强，这表明MCH以定量和定性的方式调节促黑素细胞的分泌信号。高浓度的MCH（10 μM）显著增加了α-MSH的释放。观察到10和35 μM的MCH类似物MCH(2-17)也增强了α-MSH的释放，这为高浓度MCH的刺激作用提供了进一步的证据。因此，我们得出结论，垂体促黑素细胞对MCH的反应是双相的，正如之前报道的MCH对鱼类和哺乳动物其他靶标的影响一样。在生理条件下，MCH对鱼类促黑素细胞的抑制作用很可能占主导地位。
