Specificity of Radioprotective and Cytotoxic Effects of Cysteamine in HeLa S 3 Cells: Generation of Peroxide as the Mechanism of Paradoxical Toxicity
1974; Radiation Research Society; Volume: 60; Issue: 2 Linguagem: Inglês
10.2307/3573964
ISSN1938-5404
AutoresYoshinari Takagi, Mikio Shikita, Toyozo Terasima, Sanya Akaboshi,
Tópico(s)Sulfur Compounds in Biology
ResumoCysteamine at 0.5-5 mM effectively kills ${\rm HeLa} {\rm S}_{3}$ cells, while it is much less toxic in higher concentration (30 mM). The toxicity develops gradually with time as peroxide generates in the medium. Addition of catalase and peroxidase to the culture inhibits the toxic effect of cysteamine. The results suggest that the paradoxical cell-killing action of cysteamine can be ascribed to the generation of the peroxide by the compound ( $2{\rm RSH}+{\rm O}_{2}={\rm RSSR}+{\rm H}_{2}{\rm O}_{2}$). In higher concentrations, cysteamine protects the cells by decomposing the produced peroxide ( ${\rm H}_{2}{\rm O}_{2}+2{\rm RSH}={\rm RSSR}+2{\rm H}_{2}{\rm O}$). Radioprotective effect of cysteamine is not directly related to the cytotoxic action of the compound. The magnitude of dose reduction factor (Y) is a linear function of logarithms of the concentration (X) of the compound (Y = 1.4 log X + 1.2). It is to be noted that the minimum effective concentration is about 0.7 mM and that the protective pow...
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