Immunohistochemical study on atrial natriuretic peptide in the ventricle of hearts of infants and children.

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In this study, the presence and distribution of human atrial natriuretic peptide (ANP) were i. iivestigated iijimtinoliistoclieniically in tlie ventricle of the hearts of infantsaiid children. ANP-immunoi, eactive myocytes were cleai, ly deinoiisti, at. e(i iii tlie veiiti, icle of liearts wi L. Ii endocardial fibi, oel-astosis and dilated cardioinyopat, iiy. The distri. btit. i. oii of ANP-positive inyocytes was most frequent iii the inner otie-third of tlie left ventricle. No ANP'immunoreactivity was detected in any lieart in cases with congei-iital heart disease or noncardiac disease. The left ventricular volume of liearts with ANP-positive myocytes was larger than that witli ANP-negetive myocytes. The inean diameter of ANP-positive niyocytes was greater tilail that of ANP-negative myocytes. Iminunohistochemical study was also carried out in the biopsied ventricular myocardium of endocardial fibroelastosis. The frequency of ANP-positive myocytes in the biopsied specimens significantly correlated with left ventricular end-diastolic volume (r=0.735) and inversely correlated with ejection fraction (r=0.730). It was also correlated with histopathologic severity index (inyocyte hypertrophy, degeneration and interstitial fibrosis) (r=0.762). Ultrastructural examination confirmed the presence of specific electrondense granules of 250-400 nm in diameter in the ventricular myocytes. Immunoelectron microscopy demonstrated the presence of ANP-labeling colloidal gold particles in the specific granules. It was also demonstrated that brain natriuretic peptide was colocalized with ANP in some of the granules. The results of this study suggest that ANP expression in the ventricle of heart muscle disease in infancy and childhood is related to excess of wall stresses and of myocyte stresses.