Abstract
Adult inbred Swiss mice were given a single carcinogenic dose of methyl‐labelled methylnitrosourea in the range of doses which induces thymic lymphomas, lung adenomas and other random malignant tumours. DNA was extracted from pooled bone marrow, spleens, thymuses, kidneys, livers, or lungs within 1 h of injection and was hydrolysed and chromatographed to demonstrate the proportions of three products: 7‐methylguanine, 3‐methyladenine, and 6‐methoxyguanine. Disproportionately high relative amounts of 3‐methyladenine were found in the tissues thought to have a role in the genesis of thymic lymphomas. 6‐methoxyguanine, which Loveless (1969) postulates to be the product crucial for carcinogenesis, was detected in the DNA of all tissues examined. The possible usefulness of this approach to the study of carcinogenesis was thus demonstrated.

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