Evidence That Gastrin 34 Is Preferentially Released from the Human Duodenum

A method for extraction and concentration of gastrin components from large volumes of plasma by affinity chromatography combined with gel filtration and radioimmunoassay with region-specific antibodies was used to measure gastrin components in plasma obtained from human subjects during fasting and 45 min after a mixed meal. In plasma from 6 normal and 6 unoperated duodenal ulcer subjects, gastrin 34 was twice as abundant as gastrin 17 during fasting but both components increased to a similar extent after the meal. Small but significant increases were found in component 1 but not in gastrin 14, but these forms comprised a minor fraction of total gastrin. The only significant difference found between normal and ulcer subjects was a lower amount of nonsul f ated gastrin 17, but not of total gastrin 17, in duodenal ulcer patients after the meal. In contrast, 6 fasting duodenal ulcer patients with previous subtotal gastrectomy and gastroduodenostomy had significantly lower concentrations of all gastrin components except gastrin 34 when compared with the unoperated ulcer patients and gastrin 34 was the only component that increased significantly after a meal. These results are compatable with a duodenal source of circulating gastrin. Calculations based on the known differences in concentra tion of extractable gastrin in antral mucosa (11 gastrin 34) and duodenal mucosa (57% gastrin 34) and an estimated 7.5-fold slower clearance rate of gastrin 34 compared with gastrin 17 in the circulation indicate that the duodenum could account for all basal gastrin in antrectomized patients and 40%–50% of basal gastrin in unoperated patients. Similar calculations indicate that up to one-third of gastrin released by a meal in unoperated subjects could originate in the duodenum.