Failure to induce tumors in the large intestine of Capuchin monkeys (Cebusapella) by using 1,2-dimethylhydrazine

The purpose of this study was to produce tumors in the large intestine of C apuchin Monkeys (Cebus apella) by the administration of the colonotropic ca rcinogen 1,2-dimethylhydrazine (DMH). The subjects were 12. monkeys, all ma les, age 30 months, with a mean weight of 2.858 kg. The DMH was administere d subcutaneously to six of the monkeys at a dosage of 25 mg/kg of body weig ht once a week for 16 weeks; control monkeys received an equivalent volume of the stock solution without DMH. Twenty months after administration of th e first dose, the animals were sacrificed. None of the monkeys showed intes tinal tumors. Samples of the gastrointestinal tract were removed, fixed, an d stained according to standard histological techniques. Histological chang es were seen in all of the DMH-treated animals, these consisted of glandula r hyperplasia and hyperplasia of the epithelium overlying the lymphoid nodu les. In addition, foci of dysplasia were found in three of the animals. Our results suggest that the DMH induced preneoplastic changes, characterized by hyperplasia and dysplasia, in the mucosa of the large intestine.