Analyses of the regulatory mechanisms of motile activities by factors other than neurotransmitters and hormones in teleost fish chromatophores

1.尼罗罗非鱼红细胞对365 nm、400 nm和600 nm的光直接产生色素聚集反应，而500 nm的光则诱导色素分散。用从尾鳍分离的红细胞培养液，研究了百日咳毒素、霍乱毒素、无Ca^2+、无Mg^2+的钾溶液等对红细胞光反应的影响。色素的聚集和分散反应分别与Gi和Gs有关。KT-PCR结果显示，红、绿色视蛋白基因在罗非鱼鳍中均有表达，但仅在红细胞存在的部位有表达。这些细胞的光反应取决于光强度，500 nm附近的光在诱导反射光的波长向更长波长移动方面最有效。环AMP的减少可能与光反应有关。RT-PCR结果显示视紫红质mRNA在红点鲑皮肤及视网膜中均有表达。但在肌肉组织中未检测到mRNA表达。利用离体鱼鳍和离体培养的色素细胞，研究了内皮素（ET）对鱼色素细胞的影响。ET-1、2和3可引起黑色素细胞的色素聚集和虹膜细胞的反射光波长向长波长移动，这可能是由cAMP通过Gi减少引起的。在白细胞体中，分散反应可能是由Gs介导的。经药理学分析和免疫荧光技术证实，色素细胞膜上存在ET_B受体。

1.Nile tilapia erythrophores respond directly to light at 365 nm, 400nm and 600nm by pigment aggregation, while light at 500 nm induces pigment dispersion. Using cultured erythrophores isolated from tail fins, the effects of pertussis toxin, cholera toxin, Ca^<2+> and Mg^<2+>-free K solution etc. on the photoresponses were examined. Pigment aggregation and dispersion responses were suggested to couple to Gi and Gs, respectively. KT-PCR showed the expression of mRNAs encoding red and green opsins in tilapia fins, only where erythrophores exist.2.Light-sensitive iridophores (light-reflecting chromatophores) in the skin of neon tetra were also analyzed. The photoresponses of these cells depended on the light intensity, and light near 500 nm was most effective in inducing the shift in wavelengths of reflected light toward longer wavelengths. The decrease in cyclic AMP may be related in the photoresponse. RT-PCR showed the expression of rhodopsin mRNA in the skin of neontetra, in addition to retina. However, the mRNA expression was not detected in muscle tissues. Cloning of cDNA of neon tetra rhodopsin was also performed.3.Using split tail-fin preparations and cultured chromatophores, the effects of endothelin(ET) on fish chromatophores were examined. ET-1,2 and 3 were found to cause pigment aggregation in melanophores and the shift in wavelengths of reflected light toward longer wavelengths in iridophores, which may be triggered by the decrease in cAMP via Gi. In leucophores, dispersion responses were induced probably mediated by Gs. By pharmacological analyses and immunofluorescence technique, it was suggested that ET_B receptors were present in the chromatophore membrane.