Radiosensitization mechanism of riboflavin in vitro

Riboflavin, suggested to be a radiosensitizer, was studied in murine thymocytes and human hepatoma L02 cell line in vitro with MTT method and fluorescence microscopy. When the murine thymocytes treated with 5-400 μmol/L riboflavin were irradiated by 5 Gy 60Co γionizing radiation, the low concentration groups, i.e. treated with 5-50 μmol/L riboflavin, showed a different surviving fractions-time relating correlation compared with the high concentration groups, i.e. treated with 100-400 μmol/L riboflavin. The former had a high survival level at the end of irradiation, but which, after 4-h incubation, decreased rapidly to a low level. On the contrary, the high concentration groups showed a low survival level at the end of irradiation, and a poor correlation was found between the surviving fraction and the incubation time, after 4 h a little difference was observed. The results of fluorescence microscopy indicated that under low concentration conditions, the riboflavin localized mainly in nucleus (both pe     

Radiosensitization mechanism of riboflavin in vitro

Riboflavin, suggested to be a radiosensitizer, was studied in murine thymocytes and human hepatoma L02 cell line in vitro with MTT method and fluorescence microscopy. When the murine thymocytes treated with 5–400 μmol/L riboflavin were irradiated by 5 Gy ⁶⁰Co γ ionizing radiation, the low concentration groups, i.e. treated with 5–50 μmol/L riboflavin, showed a different surviving fractions-time relating correlation compared with the high concentration groups, i.e. treated with 100–400 μmol/L riboflavin. The former had a high survival level at the end of irradiation, but which, after 4-h incubation, decreased rapidly to a low level. On the contrary, the high concentration groups showed a low survival level at the end of irradiation, and a poor correlation was found between the surviving fraction and the incubation time, after 4 h a little difference was observed. The results of fluorescence microscopy indicated that under low concentration conditions, the riboflavin localized mainly in nucleus (both perinuclear area and inside of nuclear membrane), while under high concentration conditions, intensive riboflavin also localized around cytoplasmic membranes. Thus we can conclude: the riboflavin had radiosensitivity effect on DNA under low concentration conditions, and enhanced the damage to cytoplasmic membrane under high concentration conditions. Also the most effective concentration of riboflavin can be evaluated to be approximate 100 μmol/L.     

核黄素体外辐射增敏机理研究

采用MTT方法和荧光显微镜技术, 以小鼠胸腺细胞和人肝L02细胞株为研究对象, 对核黄素的体外辐射增敏作用进行研究. 在5 Gy ⁶⁰Co γ 射线辐照条件下, 低浓度(5~50 μmol/L)和高浓度(100~400 μmol/L)核黄素作用下的小鼠胸腺细胞存活率的时间依赖关系表现出明显的差异, 其规律为: 低浓度下, 细胞受g射线辐照后并不立刻大量死亡, 但随着时间的推移存活率迅速下降, 4 h后存活水平降低到较低的水平; 而高浓度下, 细胞立刻大量的死亡, 且随时间的变化, 细胞存活仅有微弱的下降. 荧光显微镜研究结果显示, 核黄素在细胞中的分布因高浓度和低浓度而有所不同, 低浓度时核黄素集中于细胞核区, 高浓度时细胞膜区也有较高的分布. 由此得到结论: 低浓度时(<50 μmol/L), 核黄素作用的位点在细胞核, 对DNA辐射损伤增敏; 高浓度时(>100 μmol/L), 核黄素辐射增敏的主要靶位点为细胞膜, 两者均显示出核黄素对细胞辐射损伤具有显著的增敏效应.