Dietary wheat bran modulates proliferating cell nuclear antigen-labeling index of the rat colorectum after treatment with 1,2-dimethylhydrazine

Abstract

We investigated whether dietary wheat bran (Wb) influences the proliferating cell nuclear antigen (PCNA)-labeling index (LI) of the colorectum of rats after the injection of 1,2-dimethylhydrazine (DMH). Male Wistar/ST rats were divided into four groups and given either a fiber-free diet or diets supplemented with Wb at the expense of the whole diet (5, 10 or 20 g/100 g diet). Then, they were subcutaneously injected with a single dose of DMH (20 mg/kg body weight) or the vehicle. At four weeks after the treatment, frozen sections of the colorectum were immunostained with anti-PCNA antibody (19F4). In the fiber-free group, DMH treatment significantly increased the PCNA-LI of the distal colon and rectum. Among the DMH treatment groups, the PCNA-LI of the distal colon in the Wb 5 g/100 g diet group was significantly lower than that in the fiber-free group. The PCNA-LI of the distal colon tended to increase as the amount of Wb supplemented was increased in the DMH-treated groups except for the fiber-free group. A similar trend was observed for the rectum. In conclusion, the ingestion of Wb diminished the increase in PCNA-LI in rat colorectum induced by DMH injection.