Ex vivo hemoperfused pancreaticoduodenal preparations from dogs have been used to study intraluminal and circulatory patterns of release of immunoreactive gastrin under basal conditions and after secretin stimulation. Bidirectional release of immunoreactive gastrin was maximal at 3 U/min secretin infusion, and release into pancreatic and duodenal juice exceeded that into portal venous blood. Molecular sieving chromatography of peptides with gastrin-like immunoreactivity recovered from duodenal and pancreatic juice indicated a single species of a molecular size equivalent to CCK8 and smaller than minigastrin (G-14). The exact identity has not been defined. This study demonstrates that secretin stimulates release of gastrin-like peptides into blood and lumen of extra-antral gastrin-producing tissues in the dog. Unidirectional gastrin release patterns from gastrinoma tissue may explain the paradoxical increase in plasma gastrin levels in response to secretin in patients with gastrinomas (Zollinger-Ellison syndrome).
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