Effects of a meal of fish oil or corn oil on bile flow and composition in rats previously adapted to diets containing fish oil or corn oil

Chronic feeding of diets rich in n-3 or n-6 fatty acids influences the fatty acid profile of biliary phospholipids. We have examined whether the fatty acid composition of a single meal affects the fatty acid composition of biliary phospholipids, bile flow and lipid composition. Adult male Sprague-Dawley rats were fed diets containing either corn oil or fish oil (MaxEPA) for a period of 2 weeks. At the end of the feeding period, rats were fitted with exteriorized cannulas in the duodenum and bile duct. They were then given intraduodenally a bolus of an emulsion of fish or corn oil plus sodium taurocholate. Bile was collected hourly for 6 hours. Both previous diet and the infused fat affected the fatty acid composition of bile. Bile secretion was higher in MaxEPA infused rats. Neither diet nor oil infused alone had an effect on the concentrations of biliary cholesterol or phospholipid but a significant interaction was observed between diet and oil infused. Both factors independently affected bile acid concentration. There was a decrease over time in the levels of cholesterol, phospholipid, and bile acids as well as the proportions of 18:1(n-9), 18:2(n-6), 20:4(n-6), 20:5(n-3) and 22:6(n-3) for all groups. An increase in 18:0 was observed over the 6 hour collection period, regardless of previous diet or oil infused. The results indicate that 1) 18:1(n-9), 20:5(n-3), and 22:6(n-3) in bile phospholipids are influenced by the previous diet and the fat infused, 2) the type of fat in the diet or a meal can alter bile flow and, 3) Combined, diet and infused fat had a significant effect on the concentrations of biliary cholesterol and phospholipids but independently affected bile acid secretion.