Additive effect in the induction of kidney tumours in rats treated with dimethylnitrosamine and ethylmethanesulphonate.

Wistar rats were treated with a single dose of 30 mg/kg of DMN or with single doses of 100, 200 or 300 mg/kg of EMS. Tumours of the kidney developed in a few animals receiving EMS and in 33% of the male and 63% of the female rats treated with DMN alone. In the animals receiving DMN and, 8 hours later, a single dose of 100, 200 or 300 mg/kg of EMS, an additive effect was observed in the induction of kidney tumours. This additive effect was more pronounced in female than in male rats. Morphologically, the tumours were of epithelial and mesenchymal type with a preponderance of the former type. The significance of alkylation of the nucleic acids of the kidney observed with these two compounds is discussed in relation to the present findings.