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

1.尼罗罗非鱼对365 nm、400 nm和600 nm的光有直接的色素聚集反应，而500 nm的光则引起色素的分散。以培养的尾鳍红细胞膜为材料，研究了百日咳毒素、霍乱毒素、Ca~(2+)和Gt~(2+)及无镁K~(2+)溶液等对光反应的影响。色素聚集反应和分散反应分别与GI和Gs偶联。KT-PCR显示编码红色和绿色视蛋白的mRNAs在罗非鱼鳍中的表达，只有在红细胞体存在的地方。2.还分析了霓虹鱼皮肤中的光敏虹膜生色团(光反射生色团)。这些细胞的光响应依赖于光的强度，500 nm附近的光最有效地诱导反射光的波长向更长的波长移动。环磷酸腺苷的减少可能与光反应有关。RT-PCR结果显示，除视网膜外，视紫红质在新生儿皮肤中也有表达。但在肌肉组织中未检测到该基因的表达。利用裂解尾鳍标本和培养的发色团，研究了内皮素(ET)对鱼类发色团的影响。研究发现，ET-1、2和3可引起黑素细胞色素聚集和虹膜细胞反射光波长向更长波长移动，这可能是由Gi引起的cAMP减少所致。在白血病细胞中，色散反应可能是由Gs介导的。药理分析和免疫荧光技术表明，发色细胞膜上存在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.