A sensitive sandwich-enzyme immunoassay for human endothelin.

A sensitive enzyme immunoassay (EIA) for human endothelin(1-21) has been established. The assay is based on a sandwich method that uses two differing capture and detection anti-endothelin antibodies. A monoclonal anti-endothelin antibody AwETN40, which did not react with an endothelin C-terminal heptapeptide, was used as an immobilized antibody. The Fab' fragment of rabbit antibodies against the endothelin C-terminal heptapeptide was used as an enzyme-labeled detector antibody after being coupled with horseradish peroxidase (HRP). The assay is sensitive enough to detect as little as 0.2 pg/well (80 amol/well) of endothelin. Preliminary investigations indicated that the basal level of immunoreactive endothelin in male plasma (n = 24) extracted with Seppak C-18 cartridges was 1.59 +/- 0.32 pg/ml.