EFFECTS OF DIETARY FIBER ON DIMETHYLHYDRAZINE-INDUCED CHANGES IN PROSTANOID CONCENTRATIONS IN RAT COLONIC MUCOSA

1. This study was designed to elucidate the effects of guar gum, a die tary fibre, on changes in prostanoid contents induced by 1,2-dimethylh ydrazine, a carcinogenic agent, in rat colonic mucose. 2. Prostanoid c ontents were determined using high performance liquid chromatography; five prostanoids, namely 6-keto-prostaglandin F-1 alpha, prostaglandin F-2 alpha, prostaglandin E(2), prostaglandin D-2 and thromboxane B-2, were detected. 3. Four subcutaneous injections of dimethylhydrazine, 60 mg/kg every 6 days, increased the mucosal concentrations of prostag landin E(2) and thromboxane B-2 by approximately 50%. Other prostanoid s did not change significantly throughout the experiments. 4. In rats treated with dimethylhydrazine and a fibre diet a significant increase in thromboxane B-2 content was not observed, although a significant i ncrease in prostaglandin E(2) content was observed. These effects were observed in rats fed with fibre diet over 20 days but not observed in rats fed with fibre diet over 10 days. 5. From these results and the report that aspirin use at low doses is effective in the reduction of the risk of fatal colonic cancer, inhibiting thromboxane B-2 synthesis by fibre diet might be involved in the protective effect against the occurrence of colonic cancer.