Comparison of intraduodenal and intravenous administration of amino acids on gastric secretion in healthy subjects and patients with duodenal ulcer.

Abstract

SUMMARY The ability of an amino acid mixture given intraduodenally or intravenously to stimulate gastric secretion is compared in healthy subjects and in duodenal ulcer patients. Graded amounts of amino acids by both routes produced a similar increase in acid output in healthy subjects, reaching about 30% of the maximal response to pentagastrin. Serum gastrin concentrations remained virtually unchanged but serum alpha amino acid nitrogen levels were about twice as high with intravenous as with intraduodenal administration. Intravenously administered amino acids produced a significantly higher acid output in patients with duodenal ulcer than in healthy subjects, but did not produce a significant increase in gastric acid or pepsin secretion when combined with a pentagastrin infusion as compared with pentagastrin alone. Cimetidine (2 mg/kg/h) added to intravenous amino acid infusions caused almost complete suppression of acid secretion. This study indicates that amino acids are capable of stimulating gastric secretion after intraduodenal and after intravenous administration. The response to the latter is significantly higher in patients with duodenal ulcer than in healthy subjects, does not appear to involve gastrin release, is not affected by pentagastrin, and is strongly suppressed by histamine H2-blocker.Previous studies have shown conclusively that the only known chemicals in food that stimulate gastric secretion are products of protein digestion, peptides and amino acids. The stimulation of gastric secretion by peptic digests has been attributed to the release of gastrin from the antral and intestinal G cells (Strunz et al., 1977) and to a direct action on the oxyntic glands . Unexpectedly, it has been reported recently that an amino acid mixture may stimulate gastric secretion after intravenous administration, without mediation of gastrointestinal hormones Landor and Elpidio, 1977;Landor and Ipapo, 1977).In this report, the effect of an amino acid mixture given intraduodenally on gastric acid secretion has been compared to that evoked by intravenous amino acids in patients with duodenal ulcer and in healthy subjects. ' Intraduodenal infusions were given via a double lumen gastroduodenal tube modified with two balloons. A few hours after being passed the tip was positioned at the junction of the third and fourth parts of the duodenum under fluoroscopic control and the balloons straddling the pylorus were inflated with 20 ml of air to prevent duodenogastric reflux. This caused no sensation or discomfort. The duodenal lumen was used to instill the test solution into the duodenum and the gastric lumen to aspirate gastric content (Konturek et al.,

Intravenous infusion of L-isomers of phenylalanine and tryptophan stimulate gastric acid secretion at physiologic plasma concentrations in normal subjects and after parietal cell vagotomy.

“…In man and dog, intravenous infusion of a mixture of L-amino acids increased gastric acid secretion to -30-40% of the maximal acid response to either pentagastrin or histamine (1)(2)(3)(4)(5). Furthermore, in man, equal amounts of a mixture of L-amino acids perfused either into the duodenum or infused intravenously result in equivalent increases in gastric acid secretion (1,2).…”

“…Furthermore, in man, equal amounts of a mixture of L-amino acids perfused either into the duodenum or infused intravenously result in equivalent increases in gastric acid secretion (1,2). The mechanism of action of circulating amino acids on parietal cell function is not known.…”

“…The mechanism of action of circulating amino acids on parietal cell function is not known. Since serum gastrin does not increase with either intraduodenal or intravenous amino acid infusion (1)(2)(3), it has been postulated that the intestinal phase of gastric acid secretion may be due at least in part to the direct or indirect effect of circulating amino acids on or near the parietal cell (2,6). After removal of the gastric antrum, small bowel, colon, and pancreas, Marino and Landor (7) observed that an intravenous infusion of a mixture of L-amino acids stimulated gastric acid secretion in the vagotomized dog.…”

Effect of Amino Acids on H⁺ Production by Isolated Rat Parietal Cells

“…The effect of intragastric or intraduodenal amino acids has been attributed either to the release of an acid-stimulating gastrointestinal hormone, in particular gas trin [3], or to a direct effect on the parietal cells [1,2]. More unequivocally, the effect of intravenous amino acids has been speculated to be due to a direct action on the parietal cells [2,6,8,9].…”

“…Intragastric and intrajejunal amino acids are powerful stimulants of gastric acid secre tion in man and dog [1][2][3][4], Similarly, intra venous amino acids stimulate gastric acid secretion in man and dog to about 30-60% of the maximal acid output in response to histamine, pentagastrin, or a peptone meal [2,[5][6][7][8][9][10]. The effect of intragastric or intraduodenal amino acids has been attributed either to the release of an acid-stimulating gastrointestinal hormone, in particular gas trin [3], or to a direct effect on the parietal cells [1,2].…”