Increased Expression of Aquaporin-1 on the Pleura of Rats with a Tuberculous Pleural Effusion.

The purpose of this study was to investigate whether the expression of AQP-1 on the pleura is altered in a rat model with a tuberculous pleural effusion (TPE) and to study its function. A TPE model was established by intrapleural inoculation with 0.03 mg (2 ml) standard tuberculosis bacillus (H37Rv). The rats with TPE were sacrificed at different time points (day 1, 3, or 5) after inoculation. The control group received a 2-ml intrapleural injection of saline. The visceral and parietal pleural tissues were harvested and processed for real-time RT-PCR, Western blot, immunohistochemistry, and determination of tissue AQP-1 levels. Recombinant adenovirus Ad-rAQP-1 containing full-length cDNA of AQP-1 was constructed. Six groups of seven Wistar rats were assigned to receive the following treatments: group 1: intrapleural administration of normal saline; group 2: intrapleural administration of tuberculosis bacilli (TB); group 3: intrapleural inoculation with TB at day 7 following intrapleural administration of Ad-rAQP-1 vector; group 4: intrapleural inoculation with 0.03 mg TB at day 7 following intrapleural administration of control Ad-GFP vector; group 5: intrapleural administration of Ad-rAQP-1; group 6: intrapleural administration of control Ad-GFP vector. The expression of AQP-l on the pleural tissue was detected by immunohistochemistry and Western blot analysis. Histopathologic changes of the pleura and the volume of pleural fluid were examined on day 7 following gene intervention or on day 3 following TB inoculation. Bilateral pleural effusions appeared within 5 days in all rats who received an intrapleural inoculation with TB. The peak amount of pleural fluid occurred on day 3. The AQP-1 expression at protein and mRNA was increased in the early phase of TPE. The expression of AQP-1 was increased in the Ad-rAQP-1 gene transfer group, indicating successful adenovirus gene transfer. The volume of pleural fluid in group 3 (6.1 ± 0.7 ml) was significantly increased compared with that in group 2 (3.8 ± 1.0 ml) and group 4 (4.0 ± 1.1 ml). These findings suggested that AQP-1 was increased in TPE and it may be involved in the formation of TPE. [ABSTRACT FROM AUTHOR]