Ventricular expression of atrial natriuretic peptide in chronic chagasic cardiomyopathy is not induced by myocarditis.
BACKGROUND
The ventricles of the normal heart are virtually devoid of atrial natriuretic peptide (ANP). Although ANP occurs in ventricles submitted to elevated wall stress, it is not clear whether ANP expression is affected by myocarditis. We investigated the immunohistochemical expression of ANP in chronic chagasic cardiomyopathy, an inflammatory cardiomyopathy caused by infection with the protozoan Trypanosoma cruzi.


METHODS
Necropsy samples from the left and right ventricles of 16 patients exhibiting chronic chagasic cardiomyopathy were evaluated for myocarditis, fibrosis, T. cruzi parasites and ANP immunoreactivity. The diameters of 50 myocytes per sample were measured.


RESULTS
ANP was present in myocytes of the subendocardial region in 13/16 (81.3%) left and 10/16 (62.5%) right ventricular samples (P=0.25). Myocytes present in the inflammatory foci, near the infiltrating inflammatory cells but distant from the subendocardial region, did not express ANP. Trypanosoma cruzi parasites exhibited intense immunoreactivity for ANP. The mean myocyte diameter and the incidence of myocarditis, fibrosis, and T. cruzi parasites was similar between the left and right ventricular samples. No statistical differences were found between the ANP-positive and ANP-negative cases.


CONCLUSIONS
In chronic chagasic cardiomyopathy, both ventricles exhibit hypertrophy, fibrosis and ANP in the subendocardial region. The inflammatory infiltrate does not induce ANP expression in the myocytes. Regional stress but not myocarditis itself, is probably responsible for ventricular ANP expression in myocarditis.
Benvenuti
Luiz A
LA
Laboratory of Pathology, Heart Institute (InCor), University of Sao Paulo Medical School, Av. Dr. Eneas de Carvalho Aguiar 44, 05403-000, Sao Paulo, Brazil. anpluiz@incor.usp.br
Aiello
Vera D
VD
Palomino
Suely A P
SA
Higuchi
Maria de L
Mde L
D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000032:analysis* / Q000276:immunology; D002598:Chagas Cardiomyopathy / Q000150:complications / Q000276:immunology* / Q000473:pathology*; D002648:Child; D002908:Chronic Disease; D005260:Female; D005355:Fibrosis / Q000209:etiology / Q000276:immunology / Q000473:pathology; D006352:Heart Ventricles / Q000737:chemistry* / Q000276:immunology / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018485:Muscle Fibers, Skeletal / Q000737:chemistry / Q000276:immunology / Q000473:pathology; D009205:Myocarditis / Q000209:etiology / Q000276:immunology* / Q000473:pathology*; D014349:Trypanosoma cruzi / Q000302:isolation & purification
D009320:Atrial Natriuretic Factor