Effect of type and amount of dietary fat on bile flow and composition in rats

Abstract

The output of bile and biliary components (biliary salts, phospholipids, cholesterol) during the first hour after bile duct catheterization have been determined in conscious rats fed either a commercial diet or semi-purified diets containing 7 or 20 p. 100 of corn oil or 20 p. 100 of lard or mutton tallow. In those conditions, there was no significant difference in bile or biliary salts output among the various experimental groups. On the contrary, the output of cholesterol and, to a lesser extent, that of phospholipids augmented when the percentage of corn oil in the diet was increased from 7 to 20 p. 100 ; as compared to the former group, the output of these two components was lower in the lard and mutton tallow groups. Among the groups receiving the high-fat diets, absolute and relative biliary phospholipid concentrations were highest in the lard group, while the absolute biliary cholesterol concentration was identical in the lard and mutton tallow groups but lower than in the corn oil group. The relative bile salts concentrations were significantly different in the groups fed the semi-purified diets ; the highest value was found in the mutton tallow and corn oil groups (20 p. 100). The proportions of biliary lecithins, as compared to total phospholipids, were constant in the different groups, but the fatty acid patterns of biliary lecithins varied according to the diet fed. During the 6 hrs that the enterohepatic circulation was interrupted, biliary salts and phospholipid outputs decreased from the beginning of collection to the end, particularly when the initial value was higher ; the decrease of cholesterol output was noticeable only in rats fed corn oil. From these experiments, in which dietary protein content remained constant at 17 p. 100, we concluded that dietary fats generally interfere in the synthesis and secretion of biliary components ; feeding 20 p. 100 of corn oil in the diet particularly led to increased phospholipid and cholesterol excretion through the bile. In rats fed a 20 p. 100 lard diet, biliary phospholipid output and concentration increased while the bile flow rate tended to decrease.