Abstract:OBJECTIVE: Aquaporin (AQP) is a group of cell membrane transporting proteins. The study was designed to investigate the changes of AQP_1 and AQP_5 in the lung tissue under hyperoxia and their roles in pulmonary edema. METHODS: Two hundred newborn rats were randomized into different oxygen concentrations exposure: FiO_2=0.80 (Experimental group 1), FiO_2=0.60 (Experimental group 2), FiO_2=0.40 (Experimental group 3) and FiO_2=0.21 (Air control group). Rats were sacrificed at 1, 3, 5, 7 and 14 days after the beginning of experiment (10 rats each time point). The expressions of AQP_1 and AQP_5 were examined by Western Blot. The ratio of lung wet weight to lung dry weight (wet-to-dry weight ratio, W/D), and the protein content in bronchoalveolar lavage fluid (BALF) were measured. RESULTS: Compared with the Air control group, the W/D ratio and the protein content in BALF in the three experiment groups increased significantly and the increased extent was positively related to the duration and the oxygen concentration of hyperoxia-exposure. The expression of AQP_1 in the experimental groups began to decrease at the 3rd day and significant differences were found at the 5th and the 7th days after hyperoxia-exposure compared with that in the Air control group (P<0.05). The AQP_1 expression was restored somewhat at the 14th day after hyperoxia-exposure, but it was still lower in the Experimental groups 1 and 2 than that in the Air control group (P<0.05). The expression of AQP_5 in the experimental groups were reduced compared with that in the Air control group 3 days after hyperoxia-exposure and the decrease of AQP_5 expression was associated with duration of hyperoxia-exposure. The comparison among three experimental groups showed that the decrease of AQP_1 and AQP_5 expressions was associated with the concentration of hyperoxia-exposure. CONSUIONS: The expressions of AQP_1 and AQP_5 decreased in hyperoxia-induced lung injury and correlated with the severity of pulmonary edema.
