期刊
COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY C-TOXICOLOGY & PHARMACOLOGY
卷 129, 期 2, 页码 75-84出版社
ELSEVIER SCIENCE INC
DOI: 10.1016/S1532-0456(01)00187-9
关键词
erythrophores; cAMP; chromatophores; fish; leucophores; melanin-concentrating hormone (MCH); melanophores; melanin-concentrating hormone (MCH) receptor; xanthophores
In melanophores of the peppered catfish and the Nile tilapia, melanin-concentrating hormone (MCH) at low doses (< 1 muM) induced pigment aggregation, and the aggregated state was maintained in the presence of MCH. However, at higher MCH concentrations (such as I and 10 muM), pigment aggregation was immediately followed by some re-dispersion, even in the continued presence of MCH, which led to an apparent decrease in aggregation. This pigment-dispersing activity at higher concentrations of MCH required extracellular Ca2+ ions. By contrast, medaka melanophores responded to MCH only by pigment aggregation, even at the highest concentration employed (10 muM). Since it is known that medaka melanophores possess specific receptors for cr-melanophore-stimulating hormone (alpha -MSH), the possibility that interaction between M:SH receptors and MCH at high doses in the presence of Ca2+ might cause pigment dispersion is ruled out. Cyclic MCH analogs, MCH (1-14) and MCH (5-17), failed to induce pigment dispersion, whereas they induced aggregation of melanin granules. These results suggest that another type of MCH receptor that mediates pigment dispersion is present in catfish and tilapia melanophores, and that intact MCH may be the only molecule that can bind to these receptors. Determinations of cAMP content in melanophores, which were isolated from the skin of three fish species and treated with 10 nM or 10 muM MCH, indicate that MCH receptors mediating aggregation may be coupled with Gi protein, whereas MCH receptors that mediate dispersion may be linked to Gs. The response of erythrophores, xanthophores and leucophores to MCH at various concentrations was also examined, and the results suggest that the distribution patterns of the two types of MCH receptors may differ among fish species and among types of chromatophore in the same fish. (C) 2001 Elsevier Science Inc. All rights reserved.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据