Differences in Insulin, Growth Hormone and Pancreatic Enzyme Secretion after Intravenous and Intraduodenal Administration of Mixed Amino Acids in Man

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Abstract
To determine whether intestinal hormones have a physiologic role in amino-acid-induced secretion of insulin, growth hormone and pancreatic enzymes, 42 metabolically normal human subjects were studied. An amino acid mixture (30 g) was administered intravenously and intraduodenally. A higher rise in serum insulin occurred after the intraduodenal application, and took place before the maximum blood concentration of amino acids was reached. Blood sugar, nonesterified fatty acids and free glycerol concentrations fell more clearly after intraduodenal administration. The route of administration did not significantly affect blood concentrations of growth hormone. After intraduodenal amino acids, the volume and bicarbonate contents of the duodenal juice rose slightly, whereas trypsin and bilirubin content increased considerably. These results suggest that, after oral administration of amino acids in man, only the secretion of insulin is clearly influenced by intestinal factors. Much evidence suggests that cholecystokinin-pancreozymin is such a factor. (N Engl J Med 288:1199–1202, 1973)