Secretory Granules Containing Atrial Natriuretic Polypeptide in Human Ventricular Cardiomyocytes An Electron Microscopic Immunocytochemical Study

An electron microscopic immunocytochemical study of left ventricular myocardium was carried out in 16 patients with heart disease of various etiologies in order to characterize the secretory granules arising in the ventricular muscle cells. The electron-dense granules observed in the ventricular muscle cells were demonstrated only in 3 patients with dilated cardiomyopathy and chronic congestive heart failure. They were scattered throughout the cytoplasm of the ventricular muscle cells at paranuclear, interfibrillar and subsarcolemmal areas, and tended to be most numerous in the vicinity of the Golgi apparatus. These granules were often found to be bound by limiting membranes of homogeneous electron density. Protein A-gold electron microscopic immunocytochemistry with anti-α-human atrial natriuretic polypeptide resulted in specific staining of the granules. These findings, taken together indicate that the secretory granules containing atrial natriuretic polypeptide (ANP) exist in the ventricular muscle cells in a particular category of patients with dilated cardiomyopathy and chronic congestive heart failure. Thus, it is suggested that human ventricular muscle cells have retained the genetic ability to form specific ANP-containing granules in certain clinical disorders.