Expression and transport function of epithelial sodium channel in alveolar epithelial type Ⅱ cells of hyperoxia-exposed neonatal rat / 中国小儿急救医学

ABSTRACT

Objective To investigate the effect of hyperoxia on the expression and transport function of epithelial sodium channel (ENaC) in neonatal rat alveolar epithelial type Ⅱ(AT Ⅱ) cells.Methods AT Ⅱ cells were isolated from neonatal rats,and primarily cultured under hyperoxic or normoxic conditions.Western blot was applied to examine the ENaC expression,and the amiloride-sensitive Na + currents were recorded using the whole-cell patch clamp technique.Results Hyperoxia upregulate the expression of β-ENaC and γ-ENaC subunits in the neonatal rat ATⅡ cells(β-ENaC1 d0.43 ±0.06 vs0.32 ±0.04,P =0.047;2 d0.73±0.06 vs 0.50±0.08,P =0.019;3 d0.72 ±0.08 vs 0.52 ±0.06,P =0.027;γ-ENaC1 d0.64±0.05 vs0.53 ±0.05,P =0.044;2 d0.76 ±0.03 vs 0.52 ±0.04,P =0.001 ;3 d0.77 ±0.06 vs 0.61 ±0.05,P =0.025).In addition,the amiloride-sensitive Na+ currents in hyperoxia-exposed AT Ⅱ cells were also increased (1d13.71 ±2.77 vs8.92±1.38,P＜0.001;2d29.12±11.03 vs 10.41 ±1.80,P＜0.001),which was consistent with the upregulated expression of β-ENaC and γ-ENaC.However,the expression of α-ENaC was inhibited by hyperoxia to some extent (1 d0.31 ± 0.05 vs 0.46 ± 0.05,P =0.025 ; 2 d0.30 ±0.01 vs0.38±0.02,P=0.002;3d0.37±0.06 vs 0.37 ± 0.08,P =0.983).Conclusion Hyperoxia enhanced the transport function of ENaC in neonatal rat AT Ⅱ cells.Dysfunctional transport of Na + may not be a key factor involving in pulmonary edema at the early stage of bronchopulmonary dysplasia.