THE INFLUENCE OF INTRAVENOUS INFUSIONS OF GLUCOSE AND AMINO-ACIDS ON PANCREATIC-ENZYME AND MUCOSAL PROTEIN-SYNTHESIS IN HUMAN-SUBJECTS

Background Animal studies have shown that the synthesis and secretion of pancreatic enzymes and the turnover of mucosal proteins is strongly influenced by diet. Methods: To determine whether the absorbed produc ts of digestion are responsible for these changes, we investigated in groups of five healthy volunteers, the effects of TV infusions of amin o acids (0.08 g/kg/h) and glucose (0.3 g/kg/h) on pancreatic enzyme an d mucosal protein synthesis. Proteins were labeled in vivo by a 4-hour s TV infusion of C-14-leucine and the enteric infusion of H-3-leucine tracer, during simultaneous cholecystokinin stimulation and duodenal c ollection of secreted pancreatic enzymes. Labeling of mucosal proteins was measured by endoscopic biopsy. Results: The amino acid infusions elevated plasma amino acid levels, and the glucose infusions increased both glucose and insulin concentrations. The rates for amylase and tr ypsin secretion were significantly lower during the first 2 hours of g lucose infusion and the rate of synthesis of trypsin was delayed by IV amino acid infusions from 52.1 +/- 4.1 to 77.6 +/- 8.5 minutes. Mucos al protein turnover rates were unaffected. H-3-labeling via the entera l route showed similar enzyme synthesis rates but variable mucosal inc orporation rates. Conclusions: TV nutrients do not appear to stimulate the synthesis of pancreatic and mucosal proteins in human subjects.