THE EFFECT ON THE KM FOR RADIOSENSITIZATION AT 0-DEGREES-C OF THIOL DEPLETION BY DIETHYLMALEATE PRETREATMENT - QUANTITATIVE DIFFERENCES FOUND USING THE RADIATION SENSITIZING AGENT MISONIDAZOLE OR OXYGEN
THE EFFECT ON THE KM FOR RADIOSENSITIZATION AT 0-DEGREES-C OF THIOL DEPLETION BY DIETHYLMALEATE PRETREATMENT - QUANTITATIVE DIFFERENCES FOUND USING THE RADIATION SENSITIZING AGENT MISONIDAZOLE OR OXYGEN
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DOI：
10.2307/3576058
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发表时间：
1984-01-01
影响因子：
3.4
通讯作者：
BUMP, EA
中科院分区：
文献类型：
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作者：
KOCH, CJ;STOBBE, CC;BUMP, EA
用150 μ M马来酸二乙酯在37 ℃预处理V79-WNRE细胞[中国仓鼠肺] 1小时。C引起细胞内谷胱甘肽水平降低至约对照水平的10-15%（0.5与5.0 nmol/106个细胞）。可以洗涤细胞使其不含马来酸二乙酯并保持在0 ℃。C几个小时，没有毒性和谷胱甘肽浓度没有增加，虽然谷胱甘肽浓度迅速增加到正常水平，在较高的温度。生存曲线被确定为O2或米索咪唑浓度的函数（后者在没有O2的情况下）。一种新的薄膜技术被用来避免由于放射化学或细胞O2消耗而引起的O2浓度变化。谷氨酸耗竭本身引起缺氧细胞的小但一致的放射增敏（剂量增强比为1.2）。然而，谷胱甘肽耗尽引起了深刻的变化，米索硝唑的放射增敏效率，减少约2倍的Km从0.6至0.09 mM。相比之下，只有2.5倍的减少被发现在Km的放射增敏O2与马来酸二乙酯预处理。这些结果表明，一个基本的问题与传统的理论的辐射敏感性，即一个一阶竞争与目标自由基之间的自由基固定与自由基修复物种的反应必须被考虑。这也表明，谷胱甘肽作为唯一的内源性保护物种的解释困难。
Pretreatment of V79-WNRE cells [Chinese hamster lung] with 150 .mu.M diethylmaleate for 1 h at 37.degree. C caused a decrease in intracellular glutathione levels to .apprx. 10-15% of control levels (0.5 vs. 5.0 nmol/106 cells). The cells could be washed free of diethylmaleate and held at 0.degree. C for several hours without toxicity and with no increase in glutathione concentration, although the glutathione concentration rapidly increased to normal levels at higher temperatures. Survival curves were determined as a function of O2 or misonidazole concentration (the latter in the absence of O2). A new thin-film technique was used to avoid changes in O2 concentration because of radiochemical or cellular O2 consumption. Glutathione depletion itself caused a small but consistent radiosensitization of hypoxic cells (dose enhancement ratio of 1.2). However, glutathione depletion caused a profound change in the radiosensitizing efficiency of misonidazole, with a decrease in Km of about 2-fold from 0.6 to 0.09 mM. In contrast, only a 2.5-fold decrease was found in the Km for radiosensitization by O2 with diethylmaleate pretreatment. These results suggest a fundamental problem with the conventional theory of radiosensitivity whereby a first-order competition for reaction with target radicals between radical-fixing vs. radical-repairing species must be considered. It also suggests difficulties in the interpretation of glutathione as the only endogenous protective species.