Role of Peroxide in the Radioprotective Action of Thiols in E. Coli

Author： Näslund Maria Fedorcsák I. Ehrenberg L.

ISSN： 1362-3095

Source： International Journal of Radiation Biology, Vol.29, Iss.6, 1976-06, pp. : 501-511

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Abstract

The radioprotective action of cysteamine (MEA) and cysteine in E. coli is due partly to autoxidatively generated hydrogen peroxide (H₂O₂). This effect, which predominates at low concentrations of the thiols (1-2 mM in neutral solution), is regularly correlated with a metabolic block, measured as inhibition of RNA synthesis. In experiments with E. coli 15 (autotroph) under exponential growth in complete medium, the role of H₂O₂ was demonstrated by (a) a decreased radioprotective action if catalase was present in the medium; (b) a radioprotective action of H₂O₂ added to the medium; (c) a decreased protective action in the absence of catalytically active copper; and (d) oxygen being required for the radioprotective action to develop. At higher concentrations of the thiols, their radioprotective action, and the accompanying metabolic block, are less dependent on H₂O₂ generation and presumably due to a different mechanism. The radioprotective action of H₂O₂ is possibly related to the radioprotective action in mammals of catalase inhibitors.

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