CYTOTOXIC EFFECTS OF UVA-IRRADIATED RIBOFLAVIN SOLUTION AND THE DEGENERATION OF ELASTIC FIBER

核黄素溶液辐照产生较强的细胞毒性，过氧化氢酶可消除这种毒性，表明核黄素溶液的细胞毒性来源于过氧化氢。核黄素辐照溶液和HP浓度相同的辐照溶液具有相似的细胞毒性，支持了这一观点。用辣根过氧化物酶测定HP，其吸收光谱在与HP结合时发生变化。核黄素溶液在低氧条件下辐照后细胞毒性增强。这一增长是由于在接触的早期阶段HP产生得更快。如果核黄素溶液在缺氧或常氧条件下以足够剂量照射，两种溶液的细胞毒性相似。核黄素用玻璃过滤汞灯照射。DMPO检测诱导自由基。羟基自由基、核黄素自由基和超氧化物被捕获。羟基自由基在早期产生较多，核黄素自由基从照射2 min左右开始持续产生。弹力蛋白暴露于有核黄素或HP存在的UVA中。这些处理不影响处理后的弹性蛋白的消化率。将弹性蛋白与弹性蛋白酶溶解后，用不同浓度的HP处理。溶液浓度越高，弹性蛋白的吸收谱变化越快。溶解弹性蛋白的最终吸收光谱与允许自发变化的吸收光谱非常相似。

Irradiation of riboflavin solution produced strong cytotoxicity which was eliminated by the treatment of the irradiated solution with catalase, suggesting that the cytotoxicity was derived from hydrogen peroxide (HP) . This suggestion was supported by the similar cytotoxicities between the irradiated riboflavin solution and the same concentration of HP as the irradiated solution contained. Measurement of HP was carried out with horseradish peroxidase whose absorption spectrum changes when it binds to HP.The cytotoxicity of riboflavin solution increased when the solution was irradiated under hypoxic conditions. The increase was due to sooner production of HP at the early phase of exposure. If riboflavin solution was irradiated at sufficient doses under either hypoxic or normoxic conditions, the cytotoxicities of either solution were similar.Riboflavin was irradiated with a glass-filtered mercury lamp. Induced radicals were detected with DMPO.Hydroxyl radicals, ribofravin radicals, and superoxide were trapped. Hydroxyl radicals were produced much more at the early phase and riboflavin radicals constatly from about 2 min irradiation period.Elastin was exposed to UVA in the presence of riboflavin or to HP.These treatments did not affect the rate of elastase digestion of the treated elastin. After elastin was solubilized with elastase, it was treated with HP at various concentration. Solubilized elastin changed its pattern of absorption spectrum faster at the higher concentration. The final absorption spectrum of solubilized elastin was very similar to that which was allowed to change spontaneously.