Tests for a Role of H 2 O 2 in X-Ray Mutagenesis II. Attempts to Induce Mutations by Peroxide

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Abstract
On the basis of the theory developed in the first paper of this series, the amount of exposure of micronuclei of Paramecium aurelia to H2O2 was calcu-lated for irradiation experiments and experiments in which the peroxide was added to the medium. The results show that exposures to peroxide many times the amount which mutagenic doses of radiation could produce are without detectable mutagenic effect whether the peroxide is used by itself or in conjunction with X-rays. High concentrations of peroxide for brief periods of time are also not mutagenic. It is concluded that the oxygen sensitive portion of X-ray mutagenesis is not the result of H2O2 formation but involves some other mechanism such as HO2 formation or reactions between damaged chromosomes and oxygen. The few cases in which H2O2 has been shown to play an important role in mediating X-ray damage do not involve low dose processes such as mutagenesis but high dose processes occurring under conditions in which H2O2 is not rapidly destroyed.