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Int J Clin Exp Pathol 2013;6(11):2333-2341

Original Article
Effects of low-frequency noise on cardiac collagen and cardiomyocyte ultrastructure: an
immunohistochemical and electron microscopy study

Eduardo Antunes, Gonçalo Borrecho, Pedro Oliveira, António P Alves de Matos, José Brito, Artur Águas, José Martins dos Santos

Center for Interdisciplinary Research Egas Moniz, Health Sciences Institute, Monte de Caparica, Caparica, Portugal; Department of Anatomy
and UMIB of ICBAS, Abel Salazar Institute for Biomedical Sciences, University of Porto, Porto, Portugal

Received August 22, 2013; Accepted September 7, 2013; Epub October 15, 2013; Published November 1, 2013

Abstract: Introduction: Low-frequency noise (LFN) leads to the development of tissue fibrosis. We previously reported the development of
myocardial and perivascular fibrosis and a reduction of cardiac connexin43 in rats, but data is lacking concerning the affected type of collagen
as well as the ultrastructural myocardial modifications. Objectives: The aim of this study was to quantify cardiac collagens I and III and to
evaluate myocardial ultrastructural changes in Wistar rats exposed to LFN. Methods: Two groups of rats were considered: A LFN-exposed
group with 8 rats continuously submitted to LFN during 3 months and a control group with 8 rats. The hearts were sectioned and the
mid-ventricular fragment was selected. After immunohistochemical evaluation, quantification of the collagens and muscle were performed
using the image J software in the left ventricle, interventricular septum and right ventricle and the collagen I/muscle and collagen III/muscle
ratios were calculated. Transmission electron microscopy (TEM) was used to analyze mid-ventricular samples taken from each group. Results:
The collagen I/muscle and collagen III/muscle ratios increased in totum respectively 80% (p<0.001) and 57.4% (p<0.05) in LFN-exposed rats.
TEM showed interstitial collagen deposits and changes in mitochondria and intercalated discs of the cardiomyocytes in LFN-exposed animals.
Conclusions: LFN increases collagen I and III in the extracellular matrix and induces ultrastructural alterations in the cardiomyocytes. These
new morphological data open new and promising paths for further experimental and clinical research regarding the cardiac effects of
low-frequency noise. (IJCEP1308059).

Keywords: Low-frequency noise, collagen I and III, myocardial ultrastructure, immunohistochemistry, transmission electron microscopy

Address correspondence to: Eduardo Antunes, CIIEM, Centro de Investigação Interdisciplinar Egas Moniz, Instituto Superior das Ciências da
Saúde Egas Moniz, ISCSEM, Quinta da Granja, Monte de Caparica, 2829-511 Caparica, Portugal. E-mail: ejpantunes@sapo.pt