DIETARY MODULATION OF COLONIC MUCOSAL UROKINASE ACTIVITY IN RATS

The amount and type of dietary fibre ingested influences colonic lumin al characteristics, especially the concentration of carbohydrate ferme ntation products such as butyrate. This study aimed to assess whether diets supplemented with fibres of differing fermentability (delivering different amounts of butyrate to the colon) influence mucosal activit ies of urokinase and brush border hydrolases, and epithelial turnover. Groups of five rats were fed one of four diets containing low (2%), h ighly fermented (guar 10% or oat bran 10%) or slowly fermented fibre ( wheat bran 10%) for 4 weeks. Activities of urokinase, alkaline phospha tase, dipeptidyl peptidase IV and maltase were measured in mucosal hom ogenates of proximal and distal colon and from rectum. Proliferative k inetics were assessed in distal and proximal colon by the metaphase ar rest technique. Hydrolase activities were similar across all four diet ary groups but a significant difference was found for urokinase (P = 0 .014). This was due to a reduction in urokinase activities of > 30% at the three sites in the wheat bran group compared with the other group s. Of proliferative indices, only crypt column height differed across the groups (P = 0.038) and was highest in rats fed wheat bran and lowe st in those fed the low fibre diet (P = 0.047). The proportion of mito ses in the top one-fifth of the crypt also differed across groups (P = 0.038) due to the high values in the distal colon of the low fibre gr oup. Thus, addition of a slowly fermented (but not highly fermented) f ibre to the diet of rats reduces net urokinase activity in large bowel mucosa and increases the Life span of colonic epithelial cells withou t changing activities of brush border hydrolases.