Effect of Induced by Antibiotics on Incidence 1,2-Dimethylhydrazine of Rat Intestinal Tumors

ABSTRACT-The intestinal microftora has been shown to in-fluence the induction of chemical carcinogens responsible for intestinal tumors in animal models. For further exploration of this issue, male inbred F344 rats were administered a chemical carcinogen, l,2-dimethylhydrazine dihydrochloride (OM H), for 20 weeks. along with oral antibiotics, either tetracycline or erythro-mycin. to suppress the intestinal flora. Colon cancer incidence was lower in animals receiving antibiotics; 22 % of the erythro-mycin-treated rats and 20 % of the tetracycline-treated rats had colon tumors compared to untreated controls with a 74 % tumor incidence (P<0.002). Tumors in the small intestine also de-creased from an incidence of 48 % in the control animals to an incidence of 27 and 7%, respectively. tor the erythromycin- and tetracycline-treated rats. These findings suggested that the meta-bolic activity of the intestinal flora is related to cancer inductio