Effect of high-risk diets for colon carcinogenesis on intestinal mucosal and bacterial beta-glucuronidase activity in F344 rats.

The effect of high-protein (beef or soybean protein) and high-fat (beef fat, corn oil, or lard) diets on large intestinal bacterial and intestinal mucosal beta-glucuronidase was studied in female F344 rats maintained on these diets for two generations. Animals fed a 20% corn oil or 20% lard and 20% casein diet had a higher beta-glucuronidase activity in the contents of cecum and colon than did rats fed a 5% corn oil or lard and 20% casein diet. The cecal bacterial beta-glucuronidase activity was higher in animals fed diets with high levels of beef protein (40%) and beef fat (23%) or with high levels of soybean protein (39%) and corn oil (24%) than it was in rats fed diets containing 18.5% beef protein and 6.5% beef fat or 19% soybean protein and 5.4% corn oil. Animals fed diets containing high levels of beef protein and fat or high levels of soybean protein and corn oil had a higher small intestinal mucosal beta-glucuronidase activity than did the other groups. No significant difference was observed in the colonic mucosal beta-glucuronidase activity among the animals fed beef and soybean diets. It is concluded that diets high in fat and high or normal in protein are associated with elevated levels of bacterial beta-glucuronidase activity in the large intestine of rats.