Decreased expression of AQP1 and AQP5 in acute injured lungs in rats

OBJECTIVE: To determine if aquaporin1 (AQP1) and aquaporin5 (AQP5) are expressed in the alveolar capillary membrane in rats. Moreover, to investigate the alteration of AQP1 and AQP5 in acute injured lungs. METHODS: The distribution of AQP1 and AQP5 in alveolar capillary membrane were investigated by immunohistochemistry and immunoelectron microscopy with affinity-purified antibodies to human AQP1 and AQP5. To study the possibility that alveolar capillary membrane AQP1 and AQP5 undergo altered regulation, we established a rat model using alveolar instillation of lipopolysaccharide (LPS). RESULTS: Immunolabelling showed AQP1 was stained primarily in the microvascular endotheli a of normal lungs, while AQP5 was expressed in type I pneumocytes. Immunohisto chemical analysis showed a significant decrease in the expression of AQP1 and AQP5 in injured lungs at 4h-48h after LPS instillation. AQP1 protein was resumed partly at 24h after LPS instillation and steroid administration, whereas AQP5 was unchanged. CONCLUSION: The decreased expressions of AQP1 and AQP5 in injured lungs suggest that both of them may play a role in abnormal fluid transportation.