[Changes of the sodium channel in alveolar type II cells in pulmonary water transport in rats with oleic acid-induced acute lung injury].

OBJECTIVE: To determine the capability of alveolar fluid clearance and the changes of sodium channel in alveolar type II cells (ATII) in oleic acid-induced acute lung injury. METHODS: Forty four male Sprague-Dawley (SD) rats were randomized into a control group and an acute lung injury (ALI) group, with 22 rats in each group. The ALI model was established by oleic acid. The ATII cells were acutely isolated and purified, and the ATII cellular ultrastructure was observed by transmission electron microscope. In each group, the mRNA expression of 3 epithelial sodium channel (ENaC) subunits in acute isolated ATII cells from 8 rats were detected by reverse transcription-polymerase chain reaction (RT-PCR), while the extravascular lung water (EVLW) content was quantified in 7 rats by gravimetric measurement, and the lung histopathological changes were studies in 7 rats. RESULTS: In the ALI group, Smith lung injury score (7.6 +/- 0.8) and EVLW (0.80 +/- 0.17) ml were significantly higher than those in the control group [Smith score: (1.1 +/- 0.2), t = -20.859, P < 0.01; EVLW: (0.52 +/- 0.10) ml, t = -3.851, P < 0.01]. The transmission electron microscopic observation showed that there were degeneration, apoptosis, and lamellar body vacuolar changes in the ATII cells from the ALI rats. RT-PCR demonstrated that the alpha-subunit of the ENaC mRNA expression was the highest among the 3 subunits (F = 4.40, P = 0.02). In the ALI group, mRNA expressions of all the 3 ENaC subunits in acutely isolated ATII cells were decreased as compared to those in the control group [alpha-subunit: (51 +/- 9)% vs (82 +/- 7)%, t = 7.61, P < 0.01; beta-subunit: (13 +/- 7)% vs (25 +/- 4)%, t = 4.53, P < 0.01; gamma-subunit: (31 +/- 15)% vs (40 +/- 17)%, t = 3.01, P < 0.05; respectively]. CONCLUSIONS: The capacity of alveolar fluid clearance was attenuated in oleic acid-induced acute lung injury. The ENaC subunit mRNA levels of ATII cells were significantly decreased in ALI rats.