Inhibition of Secretin Release and Pancreatic Bicarbonate Secretion by Somatostatin Infusion in Man

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Abstract
Five healthy students were investigated on two different days with or without a constant infusion of somatostatin (500 μg/h) into an arm vein. A fluoro-scopically placed Lagerlöf tube was used for the collection of gastric and duodenal juice. After 30-min basal period, 40 ml 100 mmol/l HCl was infused into the midpart of the duodenum over 5 min through a thin catheter attached to the tube. Plasma immunoreactive secretin was measured by radioimmunoassay employing 125I-labelled synthetic secretin, antibody against synthetic secretin, and standards prepared from pure natural porcine secretin. Secretin levels without somatostatin infusion were 4.6 ±0.7 pmol/l (mean ±S.E.M.) basally and rose to a peak of 21.8 ±6.2 pmol/l after duodenal acidification (p < 0.05) and with somatostatin infusion were 4.4±0.4 pmol/l basally and rose to a peak of 6.7 ±1.7 pmol/l (n.s.) after duodenal acidification. Pancreatic bicarbonate output increased from 8.0 ±2.5 μmol/min (mean ± S.E.M.) to 283 ±44 μmol/min without somatostatin infusion (p < 0.05) and from 6.7 ±2.1 μmol/min to 70 ±13 μmol/min with somatostatin (p < 0.05). This study shows that somatostatin (500 μg/h) can inhibit the release of secretin and the pancreatic bicarbonate secretion after duodenal acidification in man.