Metabolism of 1,2-dimethylhydrazine by cultured human colon.

The overall metabolism of 1,2-dimethylhydrazine, and organotropic colon carcinogen in rodents, has been studied using human colon explant cultures. The binding level of 1,2-dimethylhydrazine to DNA which in this study includes both reaction of metabolites with DNA and incorporation of radioactive metabolites into DNA, showed a 100-fold variation among the 120 people studied. When different anatomical colonic sites were compared, the highest mean binding levels were found in the ascending and sigmoid colon. No significant difference in the median and mean binding levels were observed in nontumorous colon obtained surgically from patients with colon cancer and colon obtained from immediate autopsy, but decreased mean binding levels were seen in tissues obtained by surgery from patients with non-cancerous colonic disorders. Several exogenous chemicals were found to modify the metabolism. When the colon explants were co-incubated with 1,2-dimethylhydrazine and these chemicals, the binding level of 1,2-dimethylhydrazine to DNA was (a) increased by either indole 3-carbinol or phenobarbital, (b) decreased with disulfiram, butylated hydroxytoluene, or taurodeoxycholic acid, and (c) unaltered by lithocholic acid.