A method has been developed for the measurement of the hourly outputs into the duodenum of biliary lipids—cholesterol, bile acids, and phospholipids—in patients with an intact biliary system. This method employs duodenal intubation with two- or three-lumen tubes; liquid formula diets are infused at constant rates, and biliary lipid outputs are estimated by marker dilution techniques. Determinations can be made with either radioactive or nonradioactive markers. In this investigation, studies of biliary lipid output were carried out for periods of 18 to 30 hr. During the first 4 to 6 hr of formula infusion outputs were high due to gallbladder bile, but thereafter a steady state in output was achieved. Thus, it was concluded that during the steady state duodenal outputs corresponded to rates of hepatic secretion. In the steady state, outputs of cholesterol ranged from 28 to 85 mg per hr for different patients, and hourly variations in output were small. Average scretion rates of bile acids were much greater (234 to 1440 mg per hr), and larger fluctuations from hour to hour could probably be explained by variable rates of reabsorption of bile acids from the distal small intestine. Hourly outputs of phospholipids, which ranged from 311 to 578 mg per hr, showed less variability than did bile acids. When outputs of cholesterol, bile acids, and phospholipids were combined, a continuous pattern of total lipid composition of bile was obtained during the period of formula feeding. It was our conclusion that this method offers several advantages for the study of the metabolism of biliary lipids in man.
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