Plasma secretin concentrations and gastric pH in healthy subjects and patients with digestive diseases.

Plasma secretin concentrations were determined in healthy subjects and patients with duodenal ulcer, achlorhydria, and celiac sprue. Mean fasting plasma secretin concentrations in 26 healthy subjects and 26 duodenal ulcer patients were 6.7 +/- 0.5 and 10.2 +/- 1.2 pg/ml, respectively, and were significantly different (P less than 0.02). After ingestion of a standard meat meal, pyloric pH decreased to less than 4.5 within 15 min and plasma secretin concentrations significantly increased in all 52 subjects. In 14 subjects (seven healthy subjects and seven patients with duodenal ulcer), no significant rise in plasma secretin concentration occurred when pyloric pH was maintained at greater than 5.0 by intravenous cimetidine (600 mg) and intragastric antacid. In 10 achlorhydric patients, intragastric pH remained greater than 5.0 after the meal and plasma secretin concentrations did not change. However, plasma secretin concentrations increased significantly when 0.1 N HCl was infused in the stomach (25 mEq/hr) during the postprandial period. In all eight adult patients with celiac disease (seven untreated, one partially treated), pyloric pH remained less than 4.0 after a meal. Postprandial secretin concentrations did not increase significantly in six and showed a transient rise in two. These studies show that (1) plasma secretin concentration increases significantly after meals in healthy subjects and patients with duodenal ulcer; (2) neutralization of gastric acid and the achlorhydric state show no significant postprandial rise in plasma secretin concentration; (3) achlorhydric patients do not have a defect in secretin release in response to acid; and (4) failure of postprandial rise in plasma secretin in patients with celiac disease is attributed to impaired release of secretin and in achlorhydric patients it is attributed to lack of acid secretion.