Procarbazine hydrochlorate carcinogenesis in Osborne-Mendel rats.

3 mg/day procarbazine hydrochlorate, in a total dose of 300 mg, provoked tumours or raised their number in a variety of rat organs and tissues. 70.8% males and 92.5% females bore tumors against 16.6 and 33% of the controls. It is suggested that the lack of a specific target organ is due to the metabolic conversion of procarbazine to alkylating agents in the liver. The chemical structure, distribution of these agents within the organism and the different organ-specific enzyme activation and inhibition systems are probably responsible for the variable organotropism.