Effect of aquaporin-1 deletion on pleural fluid transport

To investigate the role of aquaporin-1 (AQP1) and sodium channel on pleural fluid transport.

Wild-type and AQP1 null mice were used in this study. After the mice were briefly anesthetized, 0.25 mL of hyperosmolar or isosmolar solution (containing terbutaline, amiloride or saline only) was infused into the pleural space. Then mice were sacrificed at scheduled times for measurement of pleural fluid osmolality or volume.

After instillation of hyperosmolar fluid into the pleural space, the osmolality of pleural fluid in wild-type mice was higher than that in AQP1 null mice killed at the same time (1, 2, 5 min). There was no difference in the isosmolar clearance between the wild-type and AQP1 null mice after injection of 0.25 mL isosmolar fluid into the pleural space. Terbutaline increased the osmotic and isosmolar fluid transport across pleura, but these effects were not influenced by AQP1 deletion. In contrast, amiloride reduced osmotic and isosmolar pleural fluid transport, and these effects were not influenced by AQP1 deletion.

AQP1 water channels facilitated osmotic fluid transport across the pleural surface. However, AQP1 did not play an important role in pleural isosmolar fluid clearance. Sodium channel may play a role in osmotic and isosmolar pleural fluid transport. The effects of sodium channel on fluid transport across pleural space were not influenced by aquaporin-1 deletion.