Radiomimetic Substances

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Abstract
The justification for the term "radiomimetic" is discussed at various levels of significance. (1) Pharmacological: mustard gas and related substances were tested for mutagenic action because of the resemblance between lesions caused by them and by X-rays. The parallelism between vesicants and mutagens is, however, not general. Much more general is the parallelism between mutagenic, carcinostatic and carcinogenic action. The common cause is their effect on the nucleus. (2) Cytogenetic level: The similarities between the effects of radiation and a number of chemicals are striking. But they are rather superficial, and there are also marked differences. The most interesting difference concerns the specificity with which certain mutagens seem to act on certain loci. Possible causes for this are discussed. (3) Biophysical level: the similarity between the effects of radiation and certain chemicals cannot legitimately be used to discredit the target theory of radiation. Conversely, it is very difficult to find evidence that any chemical is radiomimetic in the sense of being a "hit" poison. There are, however, theoretical reasons for assuming that many strong mutagens will act in this manner. (4) Chemical level: hydrogen peroxide, organic peroxides and formaldehyde in awueous solution are radiomimetic in the sense that they probably act in the same way as intermediaries in radiation mutagenesis. For other chemicals this is probably not the case. Mutagenic purines are definitely not radiomimetic in their chemical action, for they can be counteracted by antimutagens which are without effect on radiation mutagenesis.