DETECTION OF IMMUNOREACTIVE ATRIAL AND BRAIN NATRIURETIC PEPTIDES IN THE EQUINE ATRIUM

The distribution of immunoreactivity (IR) for cardiodilatin/atrial nat riuretic peptide (CDD/ANP) and brain natriuretic peptide (BNP) was exa mined immunohistochemically and immuno-electron-microscopically in the equine atrium, using specific antibodies. In the immunohistochemical studies, IR-CDD/ANP and IR-pBNP-26 (porcine BNP-26 immunoreactivity) w as detected in the cytoplasm of the auricular cardiocytes, but IR-hBNP -32 (human BNP-32 immunoreactivity) was not. The double immunogold lab elling method for IR-hBNP-28 and IR-pBNP-26 revealed that gold particl es of different sizes were located in the same secretory granules in t he cardiocyte, but no gold particles for IR-hBNP-32 were detected. The se results show that CDD/ANP and porcine BNP-like peptides are colocal ized in the same secretory granules of the equine atrium. They suggest that the equine atrium secretes both CDD/ANP and BNP-like peptides.