Kavanagh G, Crosby J, Norval M
University Department of Dermatology, Royal Infirmary, Edinburgh, U.K.
Br J Dermatol. 1995 Nov;133(5):728-31. doi: 10.1111/j.1365-2133.1995.tb02746.x.
Urocanic acid (UCA) is found in the stratum corneum as the trans-isomer and, on ultraviolet (UV) irradiation, photoisomerization into cis-UCA takes place. Cis-UCA has been suggested to play a part in UV-induced immunosuppression. In the present study, the concentration of UCA and the percentage as cis-UCA at 10 different body sites of 20 normal volunteers were analysed. A large interindividual variation in total UCA concentration was found, but the mean UCA concentration in each site was similar, other than at the sole of the foot. There was little variation in the UCA content between sites normally exposed, and not exposed, to light, but the percentage of UCA in the cis form was clearly higher at exposed areas.
尿刊酸（UCA）以反式异构体的形式存在于角质层中，在紫外线（UV）照射下会发生光异构化形成顺式UCA。有人提出顺式UCA在紫外线诱导的免疫抑制中起作用。在本研究中，分析了20名正常志愿者10个不同身体部位的UCA浓度和顺式UCA所占百分比。发现总UCA浓度存在较大的个体间差异，但除脚底外，每个部位的平均UCA浓度相似。正常暴露于光和未暴露于光的部位之间，UCA含量变化不大，但暴露区域顺式UCA的百分比明显更高。
