A monoclonal antibody against N-terminus of alpha-atrial natriuretic polypeptide (alpha-ANP): a useful tool for preferential detection of naturally circulating ANP.

A monoclonal antibody directed against the N-terminus of alpha-atrial natriuretic polypeptide (alpha-ANP), named KY-ANP-II, was produced by fusion of a non-producing mouse myeloma cell line, X63-Ag8.653, with spleen cells from a BALB/c mouse immunized with synthetic alpha-human ANP (alpha-hANP) conjugated to bovine thyroglobulin. The obtained antibody showed a high affinity for alpha-hANP with a Ka of 6.6 X 10(10) M-1. With this monoclonal antibody, a specific radioimmunoassay for alpha-hANP was established. The minimal detectable level of alpha-hANP in this radioimmunoassay was 0.8 fmol (2.5 pg)/tube, and IC50 was 8 fmol (25 pg)/tube. The radioimmunoassay recognized alpha-rat ANP on an equimolar basis, whereas there was no detectable cross-reactivity with alpha-ANP [4-28] or alpha-ANP [5-28]. Thus, the monoclonal antibody can detect a hormonal form of ANP, alpha-ANP, but not neuropeptide forms of ANP, alpha-ANP [4-28] and alpha-ANP [5-28]. These results indicate that KY-ANP-II becomes a useful tool for preferential detection of a circulating form of ANP and for investigation of the physiological and pathophysiological significance of ANP as a hormone.