| Summary: | <p>Abstract</p> <p>Background</p> <p>The intratracheal instillation of <it>Pseudomonas aeruginosa </it>entrapped in agar beads in the mouse lung leads to chronic lung infection in susceptible mouse strains. As the infection generates a strong inflammatory response with some lung edema, we tested if it could modulate the expression of genes involved in lung liquid clearance, such as the α, β and γ subunits of the epithelial sodium channel (ENaC) and the catalytic subunit of Na<sup>+</sup>-K<sup>+</sup>-ATPase.</p> <p>Methods</p> <p><it>Pseudomonas aeruginosa </it>entrapped in agar beads were instilled in the lung of resistant (BalB/c) and susceptible (DBA/2, C57BL/6 and A/J) mouse strains. The mRNA expression of ENaC and Na<sup>+</sup>-K<sup>+</sup>-ATPase subunits was tested in the lung by Northern blot following a 3 hours to 14 days infection.</p> <p>Results</p> <p>The infection of the different mouse strains evoked regulation of α and β ENaC mRNA. Following Pseudomonas instillation, the expression of αENaC mRNA decreased to a median of 43% on days 3 and 7 after infection and was still decreased to a median of 45% 14 days after infection (p < 0.05). The relative expression of βENaC mRNA was transiently increased to a median of 241%, 24 h post-infection before decreasing to a median of 43% and 54% of control on days 3 and 7 post-infection (p < 0.05). No significant modulation of γENaC mRNA was detected although the general pattern of expression of the subunit was similar to α and β subunits. No modulation of α<sub>1</sub>Na<sup>+</sup>-K<sup>+</sup>-ATPase mRNA, the catalytic subunit of the sodium pump, was recorded. The distinctive expression profiles of the three subunits were not different, between the susceptible and resistant mouse strains.</p> <p>Conclusions</p> <p>These results show that <it>Pseudomonas </it>infection, by modulating ENaC subunit expression, could influence edema formation and clearance in infected lungs.</p>
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