Action spectrum of UV-induced mutation in skin

近年来，太阳光中紫外线（UV）成分的增加对人类皮肤癌的诱发作用越来越明显，因此，确定UV诱发皮肤癌的作用光谱对于评估人群中日光诱发皮肤癌的风险具有重要意义。利用细菌lacZ基因导入的转基因小鼠穆塔^<TM>（其已被广泛用于暴露于各种诱变剂的动物体内的诱导突变的体内测定），我们研究了在UVB和UVA区域附近的各种波长的单色UV光照射的小鼠背部皮肤的诱导突变。结果表明，小于或等于334 nm的紫外光照射可剂量依赖性地增加皮肤表皮基因组中lacZ突变体的频率。在紫外线照射的皮肤表皮中获得的突变诱导作用光谱显示，在小于或等于295 nm的波长处突变诱导效率最大，并且最大值与334 nm处的最大值之间相差10，000倍。这些结果表明，UVB对皮肤癌的主要贡献与人类皮肤的日光暴露有关，并且能够定量评估暴露于已知剂量的日光的人群中皮肤癌的风险。

It is important to determine the action spectrum of ultraviolet light (UV)-induced mutation in skin for risk evaluation of sunlightinduced skin cancer in human population because the recent increase of the UV component of sunlight has caused significant induction of human skin carcinoma. Utilizing a bacterial lacZ gene-introduced transgenic mouse Muta^<TM>, which has been widely used for in vivo assay of induced mutations in an animal body exposed to various mutagens, we studied the induced mutations in mouse dorsal skin irradiated with monochromatic UV light at various wavelengths ranging around UVB and UVA regions. We showed the UV lights less than or equal to 334 nm could increase dose-dependently the frequency of the lacZ mutants in skin epidermis genome. The obtained action spectrum of mutation induction in UV-irradiated skin epidermis showed the maximum efficiency of mutation induction at the wavelengths shorter than or equal to 295 nm and 10,000-fold differences between the maximum and that at 334 nm. These results indicate the major contribution of UVB to skin cancer with the sunlight exposure of human skin and enable an quantitative evaluation of the risk of skin cancer in human population exposed to sunlight of known dose.