The aim was to analyze whether pericardial tissue expresses endothelial NO synthase (eNOS) protein and to determine the presence of cytosolic proteins that bind to eNOS mRNA. The effect of aspirin on the above-mentioned parameters was also analyzed. eNOS protein was expressed in pericardial tissue from male guinea pigs. Escherichia coli lipopolysaccharide (LPS, 10 g/mL) and Staphylococcus aureus endotoxin (SA, 10 g/mL) reduced eNOS protein expression and shortened the half-life of the eNOS

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... nger. Under basal conditions, cytosolic extracts from pericardial samples bound to the 3Ј-untranslated region (3Ј-UTR) of eNOS mRNA, which was enhanced by LPS and SA. Proteinase K fully prevented the binding of cytosolic pericardial extracts to 3Ј-UTR of eNOS mRNA, suggesting the involvement of proteins that were further characterized as 60-and 51-kDa proteins. Aspirin (1 to 10 mmol/L) restored eNOS expression in either LPS-and SA-stimulated pericardial samples and reduced the binding activity of the pericardial cytosolic proteins to 3Ј-UTR of eNOS mRNA. Indomethacin also reduced the downregulation of eNOS by LPS and diminished the binding activity of the cytosolic proteins, although higher doses of indomethacin than of aspirin were needed to improve these parameters. In conclusion, eNOS protein is expressed in guinea pig pericardial tissue. LPS and SA stimulate the binding activity of pericardial cytosolic proteins to 3Ј-UTR of eNOS mRNA and reduce eNOS protein expression. High doses of aspirin and indomethacin protect eNOS protein expression and reduce the binding activity of the cytosolic proteins to 3Ј-UTR of eNOS mRNA, suggesting an inverse association between the presence of these cytosolic proteins and eNOS expression. (Circ Res. 2002;90:719-727.)