[Effect of the rhythm of administration of 1,2-dimethylhydrazine on its carcinogenic action]

The regimen of DMH treatment with the same total dose influenced the realization of its carcinogenic effect. The most extensive intestinal tumours were observed when DMH was administered once a week in a dose of 21 mg/kg of body weight. Daily treatment in a dose of 3 mg per kg results in development of a less marked malignant tumour process restricted to the colon alone. However, under such conditions the liver displayed marked dystrophic and necrobiotic lesions and occasionally tumours as well. Frequent entry of the carcinogen in small doses into the organism led to a significant decrease of cytochrome P450 content in the liver microsomes. This apparently slowed down the DMH metabolism, its conversion into the proximal metabolite and the binding of the latter to the macromolecules of enterocytes.