Inhibition of gastric acid secretion in insulin tests before and after vagotomy for duodenal ulcer.

One hundred preoperative insulin tests and 165 tests one to three years after parietal cell vagotomy were analysed with regard to inhibition of gastric acid secretion by insulin. With an insulin dose of 0.2 IU/kg inhibition was seen in about one third of the tests. The lowest value and the reduction of blood sugar concentration were similar regardless of whether the test revealed inhibition or not. A late positive response was just as common in tests with and without inhibition, but there were significantly fewer early positive responses in tests showing inhibition. Basal acid output and insulin-stimulated peak acid output were similar in preoperative tests with and without inhibition, but in postoperative tests both acid secretion values were lower if inhibition was present. Although inhibition may be independent of the vagus nerve, it can modify the test response and should probably be taken into account when evaluating the clinical significance of the insulin test result.