Size and Charge Distinctions Between Endogenous Human Plasma Gastrin in Peripheral Blood and Heptadecapeptide Gastrins

Abstract

The major fraction of immunoreactive plasma gastrin in peripheral blood, cross-reacting in a radioimmunoassay system with 125I-porcine gastrin I, exhibits less acidic behavior on starch gel and paper electrophoresis and a larger molecular size on Sephadex gel filtration than that shown by heptadecapeptide gastrins. The plasma hormone is not altered by boiling and could not be shown to be converted by antral aqueous extracts to heptadecapeptide-like gastrin. From the electrophoretic and filtration behavior of plasma gastrin, it is suggested that the major fraction of the plasma hormone is a molecule of approximately 7000 mol wt containing heptadecapeptide gastrin linked to a more basic peptide. A small fraction of plasma hormone exhibits characteristics similar to heptadecapeptide gastrin.