Study on the Carcinogenicity of Chlordimeform III. Long-Term Feeding Assay in Mice

Abstract

The carcinogenicity of purified Chlordimeform (CDM) was tested in a two-year feeding assay in male Swiss mice. Five groups, 50 each of weaning mice were used in the test. Besides one group of non-treated negative control and a positive control group (300 ppm p-Chloro-o-Toluidine), three dose levels of 20, 100 and 300 ppm of CDM were added into the feeds prepared every two weeks. On necropsy and pathological examination, no neoplastic growth was found in the natural control group, 31 tumor growths with 13 malignancies were found in the positive control group. The number of animals bearing neoplasms in the tested mice were as follows: 8 (0 malignancy); 22 (5) and 36 (16) respectively in the groups receiving the increasing level doses. The regression equation calculated is:

$${}^Y{(incidence of tumor)^{ = 0.0976 + 0.0022 X}}(ppm of CDM)$$

Major findings were hemangioma and hemangiosarcoma mostly located in the abdominal or peri-bladder adipose tissue varying from pinpoint to the size of an almond. Metastases in liver were seen in some of the specimens of the highest dose group. Dose-dependent pulmonary adenocarcinoma was also noticed (0,3,6), as were liver carcinoma, renal adenocarcinoma, intestinal carcinoma etc.