Sandwich ELISA for proANP 1-98 facilitates investigation of left ventricular dysfunction

Proatrial natriuretic peptides are proposed to be sensitive and specific markers for various stages of heart deficiency. Here we present a rapid and specific sandwich immunoassay for the measurement of proANP 1-98 in biological fluids like plasma, serum urine. No sample preparation prior to the assay is necessary. Polyclonal antibodies specific for distinct epitopes of proANP 1-98, predicted to be highly immunogenic, were raised in sheep and purified by immunoaffinity chromatography prior to use in the assay. Antigen binding sites of the antibodies were determined by epitope mapping with a set of peptide fragments. The capture antibody, specific for proANP 16-23, is coated directly onto microtiter plates. Recombinant proANP 1-98 is used as a standard. The biotinylated detection antibody, specific for proANP 80-88, is incubated simultaneously with 20microl of sample for 150 min. Signal is generated with a streptavidin-HRPO-conjugate and TMB as substrate. The detection limit of the assay is 50 pmol/l; intraassay CVs are below 5%, interassay CVs are lower than 10%. Dilution curves show good linearity, recovery of synthetic peptide ranged between 85% and 91%. Reference values from healthy volunteers range from 0 to 2000 pmol/l in human plasma. We conclude this assay is a easy to handle, quick and reliable method for routine measurement of proANP 1-98 and the presented manuscript describes the procedure and performance of this ELISA in detail.