Objective To investigate the expression of aquaporin-1（AQP-1） on pleura in rats with carrageenan-induced pleural effusion and explore the role of AQP-1 in effusion formation.Methods Fifty-six healthy Wistar rats were randomly divided into a normal control group and 6 pleuritis groups（6，12，24，36，48 and 72 h groups respectively）.The rat model of inflammatory pleurisy was induced by injecting l-Carrageenan into the pleural cavity.The expression of AQP-1 on pleura was detected with immunohistochemistry.The mRNA and protein expression of AQP-1 on visceral pleura and parietal pleura were measured by RT-PCR and Western blot assay respectively.The volume of pleural effusions were measured.Results The volume of pleural effusion was 2.10±0.22，4.10±0.15，4.40±0.36，3.20±0.27，2.60±0.18，0.12±0.02 mL in the 6，12，24，36，48 and 72 h pleuritis groups respectively.AQP-1 were mainly expressed on visceral and parietal pleural mesothelial cells and capillary endothelial cells，and significantly increased in all pleuritic rats The mRNA and protein expression of AQP-1 on parietal pleura increased after 6 h and reached peak level at 24 h in pleuritic groups.The mRNA and protein expression of AQP-1 on visceral pleura increased after 12 h and reached peak level at 24 h in pleuritic groups.The expression of AQP-1 on parietal pleura at 12 h and 24 h in pleuritic groups was correlated positively with the volume of pleural effusion（r=0.857，r=0.846，all Plt;0.01）.The expression of AQP-1 on visceral pleura at 24 h in pleuritic groups was positively correlated with the volume of pleural effusion（r=0.725，Plt;0.05）.Conclusion The expression of AQP-1 on pleura were increased in rats with e carrageenan-induced pleural effusion.AQP-1 may play a role in pleural fluid transportation in pleural effusion.