Stimulation of gastric acid secretion by intravenous amino acid infusion and its inhibition by H2-receptor antagonists ranitidine and cimetidine.
It is known that intravenous amino acid infusions stimulate gastric acid secretion. In 20 healthy volunteers we studied the effect of amino acid infusion on gastric acid secretion and inhibition of the latter by the H2-receptor antagonists ranitidine and cimetidine. Acid output was measured by modified intragastric titration. Initial stimulation of acid secretion until plateau levels was achieved by pentagastrin infusion 2 micrograms kg-1 h-1. After 30 min a standard amino acid infusion at 2.1 ml kg-1 h-1 was started, together with a bolus injection of either cimetidine 200 mg in group 1 (n = 10), or ranitidine 50 mg in group 2 (n = 10). Normal saline served as a control in both groups on a second occasion. The amino acid infusion was continued for 60 min and gastric acid output redetermined until constant. Amino acid infusion increased gastric acid secretion by 67% above submaximal pentagastrin-stimulated level in group 1 and by 47% in group 2. With concurrent administration of an H2-receptor antagonist in the presence of amino acid infusion, gastric acid secretion was inhibited by 41.4% (P less than 0.004) by cimetidine and by 52.9% (P less than 0.001) by ranitidine below initial pentagastrin-stimulated levels. In order to avoid the increased acid output produced by amino acid infusions, it therefore may be desirable to administer an H2-receptor antagonist concurrently.