Abstract
We previously have reported airway-centered fibrosis after chronic infection by Mycoplasma pulmonis (MP) in male Lewis (LEW) and Fisher (F344) rats. In that study, LEW rats had demonstrable airway fibrosis after 1 month of infection, and F344 rats had airway fibrosis after 4 months. We also demonstrated increased lung compliance, showing correlation with lung collagen content. The present study was designed to determine (1) if airway fibrosis was the inevitable result of prolonged infection or if host response is necessary for airway fibrosis, and (2) the effect of prolonged infection on lung compliance. F344 females were used because they have been shown previously to have less disease than males. In contrast to the results of MP infection in LEW rats in the previous report, chronic MP infection (4, 5.5, and 7 months) of the lower airways caused a loss of compliance and no increased in lung collagen in the F344 rats compared to controls. These results indicate that prolonged infection per se is insufficient to cause airway fibrosis. Also, the result of prolonged infection in the absence of airway fibrosis is the opposite of that found when airway fibrosis is present.
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