Enzyme Immunoassay for Secretin-like Immunoreactive Substance in Human Plasma

A sensitive and specific enzyme immunoassay (EIA) for a secretin-like immunoreactive substance (secretin-IS) was developed using a synthetic carboxy-terminal (C-terminal) fragment (residue 5-27) of a porcine secretin conjugated with β-D-galactosidase and an anti-rabbit lgG coated immunoplate. The activity of the enzyme on the plate was fluorometrically determined. The present immunoassay allows the detection of 1.7 to 67 fmol/ml (0.068 to 2.7 fmol/well) of secretin. Using the present EIA, the secretin-ISs in human plasma were determined.Moreover, significant changes in the plasma secretin-IS levels were found after the oral administration of famotidine (vs.placebo).