Radioimmunoassay for sequence 38-54 of human progastrin: increased diagnostic specificity of gastrin-cell diseases

Antisera were raised against fragment 38-54 of human progastrin. All of eight immunized rabbits responded, but only one (No. 2145) produced high-titer (3.2 x 10(4)) and high-avidity (Keff degrees = 1.2 x 10(12) l/mol) antibodies. A radioimmunoassay based on antiserum 2145 and monoiodinated gastrin-34 was specific for the N-terminal sequence of human gastrin-34. It measured concentrations of 9.7 +/- 1, 18.4 +/- 2 pmol/l (mean +/- SEM) and 1.553 (0.7-476) nmol/l (median (range], respectively, in sera from normal subjects (n = 20), patients with duodenal ulcer (n = 19), and Zollinger-Ellison patients (n = 8). Conventionally measured concentrations of carboxyamidated gastrins in the same sera were 21.4 +/- 1, 23.8 +/- 3 pmol/l (mean +/- SEM) and 0.833 (0.4-214) nmol/l (median (range)), respectively. The results show that radioimmunoassays specific for the N-terminus of human gastrin-34 discriminate between healthy subjects and patients with duodenal ulcer. The improved diagnostic specificity is due to co-measurement of unprocessed and partly processed progastrins that occur in plasma of patients with duodenal ulcer disease and gastrinomas. We suggest that conventional gastrin assays are supplemented with assays specific for the N-terminus of gastrin-34 in studies of duodenal ulcer disease.