Analyses of direct action of light on fish chromatophores

3年来(1999-2001年)的研究结果如下：1)尼罗罗非鱼鳍中的红磷对光有反应。在400-400 nm和550-600 nm的光谱范围内，色素发生聚集，而在470-530 nm之间的波长范围内，分散加速。这种反应的程度取决于光的强度。在培养的红细胞膜中也观察到了同样的反应，表明光对这些细胞有直接作用。2)我们只在有红细胞膜的情况下才检测FINS中视觉色素的mRNA表达。根据GenBank中罗非鱼视锥蛋白基因序列设计了相应的聚合酶链式反应引物。RT-PCR检测到红色视蛋白和绿色视蛋白的mRNAs表达。以这些片段为探针，对尾鳍cDAN文库进行了筛选，并测定了Opsins的全序列。以红视蛋白的cRNA为探针进行原位杂交，研究了红视蛋白mRNA在红细胞膜中的分布，发现该探针在红细胞膜中被识别。3)使用百日咳毒素、霍乱毒素和其他化学物质，我们发现光响应的色素聚集或分散分别通过GI或Gs介导，分别导致细胞内cAMP水平的降低或增加。虽然我们检测了GT mRNA在罗非鱼鳍中的表达，但没有检测到这种表达。4)在霓虹灯四色虹膜中，最小有效光强度约为3.4lx。与500或600 nm的光相比，峰值波长为550 nm的光在诱导光响应(反射光的光谱峰值向更长波长移动)方面更有效。400 nm处的光效果较差。

Results obtained for 3 years (1999-2001) are summarized as follows :1) Erythrophores present in fins of Nile tilapia respond to light. In spectral regions of 400-400 nm and 550-600 nm, pigment aggregation occurs, while dispersion is accelerated at wavelengths between 470 and 530 nm. The degree of such responses depends on the light intensity. The same responses are observed in cultured erythrophores, suggesting the direct action of light on these cells.2) We examined the expression of mRNA of visual pigments in fins only where erythrophores are present. The PCR primers were designed corresponding to the sequences of tilapia cone opsins (GenBank). RT-PCR demonstrated the expression of mRNAs of two opsins, red opsin and green opsin. Using these cDNA fragments as probes, screening of tail fin cDAN library was performed, and total sequences of the opsins were determined. With in situ hybridization using cRNA of red opsin as probe, the distribution of red opsin mRNA was investigated and the probe was recognized in erythrophores. However, further study is required.3) Using pertussis toxin, cholera toxin and other chemicals, we found that pigment aggregation or dispersion in response to light are mediated through Gi or Gs, respectively, leading to a decrease or an increase in intracellular cAMP level, respectively. Although we examined the expression of Gt mRNA in tilapia fins, such expression was not detected.4) In iridophores of the neon tetra, the minimum effective intensity of light is about 3.4 lx. Light with a peak, wavelength of 550 nm is more effective in inducing the photoresponse (a shift in the spectral peak of reflected light to longer wavelengths) compared with light at 500 or 600 nm. Light at 400 nm is less effective.