Hyperoxia down-regulates lung aquaporin5 expression in premature rats

Objective To explore the expression of lung Aquaporin5 (AQP5) in premature rats and during the process of inhaling hyperoxia. Methods Gestation 21 day Sprague-Dawley(SD) fetuses (term=22 day) were randomly divideal into control group and hyperoxia group 12～24 h after birth. Hypreoxia group was exposed to about 85% oxygen. After 1 to 14 days of exposure, lung tissue was isolated and AQP5 mRNA was detected by RT-PCR. Immunohistochemistry and Western-blot was used to detect AQP5 protein. Results The expression of lung AQP5 in premature rats persistently increased after birth, and the positive staining was restricted to the typeⅠalveolar epithelial cells. Compared with control group, the AQP5 mRNA in hyperoxia group of day 1 increased significantly (P0.05), but after exposure to hyperoxia for 4 to 14 days, the AQP5 expression resulted in a decrease of mRNA and protein(P0.05 or P0.01). Conclusion AQP5 may play a key role in the alveolar period of premature rats. Hyperoxia down-regulates the AQP5 expression, this might be an important factor for the development of hyperoxia lung injury.