A surgical model for determination of true absorption and biliary excretion of manganese in conscious swine fed commercial diets.

Some trace elements, such as Mn, Cu and Zn, are absorbed and quickly resecreted into the gut through the bile. When this occurs, the unabsorbed nutrient and the absorbed and resecreted nutrient may mix in the gut, preventing quantitative calculation of either. We have developed a surgical model that prevents this complication. Pigs (20-40 kg) were fitted with cannulas in the bile duct, lumen of the duodenum, portal vein, ileocolic vein and jugular vein. After recovery for 6-8 d, pigs were given an oral dose of 9.25 mBq of 54Mn. The flow rate of blood past the portal vein was determined by infusion of P-amino hippuric acid into the ileocolic vein. Absorption was quantified by multiplying the concentration of 54Mn in the portal blood by the flow rate. Biliary excretion was determined by quantitative collection of bile, and previously collected bile was reinfused into the gut lumen. Urine and feces were also quantitatively collected. A postoperative time of 6-8 d was sufficient for pigs to recover from the effects of surgery and anesthesia, as assessed by several measures of metabolic function and food and water intake. True absorption was calculated to be 0.5%. 54Mn in the urine and bile began to increase after 4 d. When the pigs were killed after 12 d, only 0.5% of the 54Mn remained in the carcass. Results of this study show that pigs surgically modified by the described procedure can recover fully and can serve as a model to study intestinal absorption and biliary excretion of nutrients. Furthermore, initial studies using 54Mn showed that the model is applicable to studying Mn metabolism and suggest the need for a more detailed study of Mn absorption and biliary excretion.