Effect of a chemically defined diet in liquid form on colon carcinogenesis in rats

The effects of ad libitum feeding of a chemically defined diet in liquid form on the incidence and histology of colon cancer induced by 10 weekly sc injections of 7.4 mg/kg of azoxymethane [(AOM) CAS: 25843-45-2] were investigated in W-rats. The chemically defined diet was adjusted once every 24 hours from 4 weeks before injection of the carcinogen to the end of the experiment at week 40. Oral administration of the defined diet resulted in significant increase in the incidence of colon cancer at week 40. Histologic examination showed that unlike adenocarcinomas with high mucin-producing activity, which were common in rats on pellet diet, most of the adenocarcinomas that developed in rats fed on defined diet were highly or well differentiated, with a typical glandular pattern. Administration of the chemically defined diet also resulted in marked colon mucosal hypoplasia and reduced gastrin levels in the serum at weeks 4 and 40.