[Studies on dichlorvos (DDVP). III. Testing of dichlorvos for cocarcinogenic activity in mice].

In order to clarify whether or not Dichlorvos (DDVP)--which did not exert carcinogenic effects in mice in our experiments--is cocarcinogenic, male and female mice of the strain C57Bl/6/Bln were subcutaneously injected with the carcinogen N-Nitrosodiethylamine (NDEA) and received in addition DDVP orally. For comparison NDEA and DDVP alone was administered to other groups of mice. The combined application (NDEA + DDVP) did not result in increased incidences of tumors and preneoplastic lesions as compared with the NDEA-treated groups of mice. The incidence of focal (transitional cell) hyperplasias of the urinary bladder epithelium was increased in the groups treated with NDEA + DDVP as compared to the groups with single compound treatment. There were no development of tumors and no differences in the latency periods of tumors which could be attributed to the combined treatment with NDEA + DDVP. Under these experimental conditions DDVP was not cocarcinogenic in mice.