Immunoreactive gastrin components in human serum

The apparent molecular size and charge of immunoreactive gastrin components were studied in sera from patients with pernicious anaemia or gastrinomas (the Zollinger-Ellison syndrome) by Sephadex gel filtration and aminoethylcellulose chromatography. The following serum components were distinguished: (1) a monophasic component I similar in size to proinsulin which was converted into ;little' gastrin I by trypsin digestion; (2) a biphasic component II, corresponding to ;big' gastrins I and II (Gregory and Tracy); (3) a biphasic component III corresponding to ;little' gastrins I and II (Gregory and Tracy); and (4) a biphasic component IV, corresponding to ;minigastrins' I and II (Gregory and Tracy). ;Big, big' gastrin, a plasma component found in the void volume of the Sephadex G-50 column by Yalow and Berson (1972) was undetectable in the sera investigated. A component in gastrinoma and antral mucosa extracts corresponding in size to ;big big' gastrin was detectable by the assay; the ;big big' gastrin fraction from gastrinoma tissue was heterogenous, with components of apparent MW 30 000-100 000. It is concluded that serum gastrin circulates in the form of at least four components, of which the three smaller ones are in pairs.