title: Myocardial fibrosis in rats exposed to low frequency noise.
abstract: Low frequency noise (LFN) characterized by large pressure amplitude (> or =90 dB SPL) and low frequency bands (< or =500 Hz) can lead to structural and ultrastructural modifications in the extracellular matrix of several tissues, with an abnormal proliferation of collagen and development of fibrosis. It is not known whether LFN induces similar structural alterations in the ventricular myocardium of rats.
  
  
  OBJECTIVE
  The aim of this study was to evaluate and measure the myocardial fibrosis induced by LFN.
  
  
  METHODS
  Two groups of rats were considered: group A with 26 rats continuously exposed to LFN during a period of 3 months; group B with 20 control rats.The hearts were sectioned from the ventricular apex to the atria and the mid-ventricular fragment was selected. Chromotrope-aniline blue (CAB) staining was used for histological observation. The measurement of fibrosis was performed using the computer image analysis Image J software.
  
  
  RESULTS
  Histological observation with CAB staining showed the presence of collagen deposition between the cardiomyocytes. Fibrosis increased 97.5%, 81.5% and 83.7%, respectively, in the left ventricle, interventricular septum and right ventricle, in exposed rats (P <0.001).The ratio fibrosis/muscle in left ventricle, interventricular septum and right ventricle was significantly higher in LFN exposed rats (P< 0.001).
  
  
  CONCLUSIONS
  Our study demonstrates a significant myocardial fibrosis induced by low frequency noise in rats. Our results reinforce the need for further experimental and clinical investigations concerning the effects of low frequency noise on the heart.
authors.affiliation: Center for Interdisciplinary Research Egas Moniz, Health Sciences Institute, Monte de Caparica, Portugal. ejpantunes@sapo.pt
authors.forename: Eduardo
authors.initials: E
authors.lastname: Antunes
authors.forename: Pedro
authors.initials: P
authors.lastname: Oliveira
authors.forename: Gonçalo
authors.initials: G
authors.lastname: Borrecho
authors.forename: Maria João R
authors.initials: MJ
authors.lastname: Oliveira
authors.forename: José
authors.initials: J
authors.lastname: Brito
authors.forename: Artur
authors.initials: A
authors.lastname: Aguas
authors.forename: Dos Santos José
authors.initials: dos SJ
authors.lastname: Martins
mesh_terms: D000818:Animals; D009202:Cardiomyopathies / Q000209:etiology / Q000473:pathology*; D004195:Disease Models, Animal; D004781:Environmental Exposure / Q000009:adverse effects*; D005355:Fibrosis / Q000209:etiology / Q000473:pathology; D006352:Heart Ventricles / Q000473:pathology*; D007091:Image Processing, Computer-Assisted; D009206:Myocardium / Q000473:pathology*; D009622:Noise / Q000009:adverse effects*; D051381:Rats; D017208:Rats, Wistar