Suppressing effect of croton oil on intestinal carcinogenesis induced by methylazoxymethanol acetate in rats.

The effect of croton oil on intestinal carcinogenesis by methylazoxymethanol acetate (MAM) was examined in ACI/N rats. Twenty seven male and 28 female ACI/N rats were given a single intragastric intubation of MAM at a dose of 25 mg/kg body weight, followed by croton oil at 0.25 ml/kg body weight, 3 times a week, by gastric intubation until the termination of this experiment (365 days). The animals had diarrhea with administration of the croton oil, but the diarrhea had no effect on their gain in weight. Rats from all groups surviving more than 216 days were counted as effective animals. Seventeen out of 54 effective rats which were treated with MAM and croton oil developed intestinal tumors and the incidence of the intestinal tumors was significantly less than that of the group treated with MAM alone (30 out of 50 rats, P less than 0.01). The average number of tumors per rat in the experimental group which was treated with MAM and croton oil (0.6 +/- 1.1) was also smaller than that in the group which was treated with MAM alone (1.0 +/- 1.8), although the difference was not significant. These results suggest that croton oil may suppress some tumor growth at the proper dose in intestinal carcinogenesis which is initiated by MAM.