Processing-independent radioimmunoanalysis for
progastrin showed that extracts of normal pancreatic tissue from normal subjects (n = 5) and from patients with
adenocarcinoma of the papilla of Vater (n = 4) contain
progastrin and its products. The concentrations varied from 0.1 to 5.8 pmol/g tissue, of which carboxyamidated bioactive
gastrins constituted 0.03-1.9 pmol/g. In histologically normal and nonneoplastic pancreatic tissue from patients with duodenal (n = 3) and pancreatic (n = 2)
gastrinomas the expression of
gastrin was significantly higher-14.5 pmol/g (median), of which 28% was bioactive amidated
gastrins.
Gastrin-17 was the main bioactive product, but its immediate precursor,
glycine-extended
gastrin-17, constituted the predominant part of the
preprogastrin product in pancreatic tissue. Proper
gastrinoma tissue contained several precursor forms, including intact unprocessed
progastrin. Progastrins were also found in high concentrations in plasma from the
gastrinoma patients. The results raise the possibility that increased expression of
progastrin and its products in non-neoplastic pancreatic tissue is a primary defect predisposing to
neoplasia.