A MONOCLONAL-ANTIBODY AGAINST N-TERMINUS OF ALPHA-ATRIAL NATRIURETIC POLYPEPTIDE (ALPHA-ANP) - A USEFUL TOOL FOR PREFERENTIAL DETECTION OF NATURALLY CIRCULATING ANP

Abstract

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 .times. 1010 M-1. With this monoclonal antibody, a specific radioimmuoassay 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 ng)/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.