Antioxidants and cancer. IV. Initiating activity of malonaldehyde as a carcinogen.

Malonaldeh yde was applied once to the shaved backs of mice. After daily treatment with 0.1% croton oil, 52% of the mice had tumors at 30 weeks. In the same experiment, other mice were treated once with fi-propiolactone, glycidaldehyde, or 7,12-dimethylbenz[a]anthracene DMBA), and then daily with croton oil. These animals had 44, 40, and 95% tumors, respectively, at 30 weeks. Twelve mg malonaldehyde applied daily proved toxic, sometimes fatally so. Five animals also had carcinomas of their internal organs. After daily treatment with 0.36 mg malonaldehyde, no animals died of carcinoma. The predicted reactivity of malonaldehyde was confirmed; after 1 hour, only 1.9% of the applied malcaaldehyde was detectable. All skin treated with DMBA, benzo[a]pyrene, and 3-methylcholanthrene had increased