Enzyme immunoassay of gastrin in human plasma

A sensitive and specific double-antibody enzyme immunoassay (EIA) for a gastrin-like immunoreactive substance (G-IS) in human plasma was developed. For competitive reactions, the gastrin antibody was incubated with gastrin standard (or sample) and beta-D-galactosidase labeled synthetic C-terminal gastrin I fragment (residue 2-17). Free and antibody-bound enzyme hapten were separated using an anti-rabbit IgG coated immunoplate. Activity of the enzyme on the plate was fluorometrically determined. The present immunoassay allows detection of 1 to 20 fmol/ml (2.1 to 42 pg/ml) of gastrin. The levels of G-IS determined in human plasma were 7.8 +/- 1.6 pg/ml before lunch and 26.4 +/- 8.4 pg/ml after lunch.