PROMOTION OF COLON CARCINOGENESIS THROUGH INCREASING LIPID-PEROXIDATION INDUCED IN RATS BY A HIGH CHOLESTEROL DIET

To examine the influence of hypercholesteremia on 1,2-dimethylhydrazin e (DMH)-induced rat colon cancer, Sprague-Dawley rats received dietary cholesterol (CH, 0-2%) and cholic acid (CA, 0.25%) with or without DM H (20 mg/kg, s.c. injection) for 18 weeks. The rats receiving dietary cholesterol and cholic acid all significantly increased total serum ch olesterol and lipids but only a high cholesterol diet (2% CH plus 0.25 % CA) decreased the activity of glutathione peroxidase (GSH-Px) and in creased the formation of peroxides in the colon (P < 0.01). The rats t hat received the combination of DMH and high cholesterol diet enhanced these effects. At the end of the experiment, the diet group administe red DMH and high cholesterol (2% CH plus 0.25% CA) developed colon ade noma at 50% of incidence in pathological examination, but no colon ade noma formed in the rats treated with high cholesterol alone. It is sup posed that a non-carcinogenic agent like cholesterol may potentiate th e carcinogenicity of DMH in rats via an increase of lipid peroxidation and decrease in the activity of peroxidase in the target organ.