Dietary manipulation during experimental colorectal carcinogenesis: a morphological study in the rat.

The effect of the dietary manipulation of fat and fibre on the gross pathological, histopathological and scanning electron microscopic appearances of colonic mucosa was studied before and during experimental carcinogenesis in 232 male Albino Swiss rats. Carcinogen treated animals were given 12 consecutive weekly injections of Azoxymethane in a dose of 10 mg/kg per week. The animals were divided between four dietary groups (1: high fat high fibre, 2: low fat high fibre, 3: high fat low fibre and 4: low fat low fibre). The colorectal morphology was assessed at autopsy using standard histopathological techniques. In addition, scanning electron microscopic studies on selected samples were performed. A scoring system was introduced to allow a more accurate comparison of the surface architectural appearances. The high fat low fibre diet was associated with the greatest risk for macroscopic tumour production and the low fat high fibre diet with the lowest risk. Statistically significant differences between each of the dietary groups were noted with the exception of the comparison for tumour induction between the high fat high fibre and low fat high fibre dietary groups. Histopathological analysis confirmed the inter dietary relationships with respect to the extent of neoplastic change. The scanning electron microscopic study revealed that both dietary manipulation and carcinogen treatment influenced the surface characteristics. Control animals fed diet 2 (low fat high fibre) but not treated with carcinogen, showed the greatest deviation from the normal appearances. Animals treated with carcinogen and fed diet 3 (high fat low fibre) consistently showed the greatest surface abnormalities.