Pericardial fluid, present in the pericardial space, is an filtrate of plasma enriched in molecules, such prostaglandins, atrial natriuretic factor, growth factors, endothelin-1, angiotensin converting enzyme and others. The fibronectin (FN), a ubiquitous and abundant extracellular matrix protein, is secreted by cells and is subsequently assembled into insoluble multimeric fibrils at the cell surface. In the circulanting blood plasma FN exist in a soluble dimer. This protein not only provide structural support, but also modulate cellular behavior by activating signaling pathways, which can lead the cardiac remodeling. Thus, we decided to examine the presence of FN in the pericardial fluid and verify the possibility of the mesothelial cells of the parietal pericardium can be a source of this FN. Pieces of the human parietal pericardium was fixed for approximately 24 hr, in 4% buffered-formaldehyde freshly prepared from paraformaldehyde, processed for paraffin embedding and cut into 6 micrometers sections. The slices were submitted to the immunohistochemistry for FN detection. The sections showed a label inside mesothelial cells of the pericardium, among several other structures. Control sections were negative for the reaction. Samples of the human pericardial fluid were processed by SDS-PAGE. A prominent band was detected in the silver-stained gels just above the 205-kDa marker, where FN is located. The localization of FN in the mesothelial cells associated the presence of a protein band with to similar molecular mass to FN, suggest that FN present in the pericardial fluid, could be produced locally.
Supported by: UFTM; FAPEMIG