The NH2-terminal tridecapeptide fragment of gastrin-17 in serum from duodenal ulcer patients.

The concentration of gastrin in serum from 47 fasting patients with duodenal ulcer was measured with two radioimmunoassays, one specific for the COOH- and the other specific for NH2-terminal sequence of gastrin-17. The COOH-terminal assay measured 13 +/- 2 pmol and the NH2-terminal 42 +/- 7 pmol-equivalent gastrin-17 per litre (mean +/- S.E.M.). This result, corroborated by gel chromatography, shows that an NH2-terminal fragment of gastrin-17, presumably the tridecapeptide, circulates in concentrations higher than those of the four known gastrin components. The abundance of NH2-terminal fragment in serum suggests that the complementary COOH-terminal tetrapeptide fragment of gastrin-17 is also produced in large quantities.