Inhibitory effect of jejunal high caloric nutrient load on human biliopancreatic secretion. The role of atropine, naloxone and composition of nutrient solutions

Abstract

Our previous studies shown that a high caloric load in the jejunum decreases biliopancreatic output. However, the factors responsible for this inhibition have not yet been fully assessed. In this study, we have compared the effect of a high caloric load of either proteins or carbohydrates on stimulated pancreatic output and investigated the mechanism of this inhibition. The small intestine of 6 healthy volunteers was intubated 10 cm below the angle of Treitz, for 3 consecutive days, to infuse test solutions. After a 90 min period of stimulation, using a protein solution (0.6 kcal/min; solution A), one of the following 2 solutions was infused on for 90 min each day, in random order. In each instance, either a protein plus carbohydrate solution (3.5 kcal/min; solution B), or a protein solution (3.5 kcal/min; solution C) was administered. On the 3rd day, first solution A then solution B were infused with either IV atropine (17 μg/kg/h) in 3 subjects, or naloxone (40 μg/kg/hl) in 3 subjects. PEG 4000 was also added to solutions B and C and 14C-PEG to solution A, as nonabsorbable markers. Intraluminal content was aspirated 25 cm below the infusion point and 50 cm distally to prevent unabsorbed nutrients from reaching the ileum. Solution B and C caused similar decreases in lipase, chymotrypsin and bile salt outputs. Neither atropine nor naloxone inhibited the jejunal-brake induced by solution B. However, naloxone, but not atropine, decreased the carbohydrate absorption rate of solution B. In conclusion, a high caloric load of proteins or carbohydrates infused into the human jejunum decreased the bilio-pancreatic output induced by a low caloric load of proteins. This mechanism is neither cholinergic nor opioid dependent. This effect, in relation to a jejunal brake, might explain functional pancreatic insufficiency after surgical procedures such as gastro-jejunostomy.