EFFECT OF TYPE AND AMOUNT OF DIETARY-FAT ON BILE-FLOW AND COMPOSITION IN RATS

The output of bile and biliary components (biliary salts, phospholipids, cholesterol) during the 1st h after bile duct catheterization were determined in conscious rats fed a commercial diet or semi-purified diets containing 7 or 20% corn oil or 20% of lard or mutton tallow. There was no significant difference in bile or biliary salts output among the various experimental groups. The output of cholesterol and, to a lesser extent, phospholipids increased when the percentage of corn oil in the diet was increased from 7 to 20%; compared by the former group, the output of these 2 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 identifical in the lard and mutton tallow groups but lower than in the corn oil group. The relative bile salts concentrations were significant different in the groups fed the semi-purified diets; the highest value was found in the mutton tallow and corn oil groups (20%). The proportions of biliary lecithins 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 h 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. When dietary protein content remained constant at 17%, dietary fats generally interfere in the synthesis and secretion of biliary components; feeding 20% of corn oil in the diet particularly led to increased phospholipid and cholesterol excretion through the bile. In rats fed a 20% lard diet, biliary phospholipid output and concentration increased while the bile flow rate tended to decrease.