Fig. 1.

Effects of hyperoxia exposure on the structure and function of the pulmonary epithelial barrier in vitro. Alveolar cell monolayers were exposed to normoxia (N) (21 % O₂/5 % CO₂) or hyperoxia (H) (85 % O₂/5 % CO₂) for 0, 24, 48, and 72 h. Tight junction structures (a, b, c, d; 20,000× or 80,000×) were determined by transmission electron microscopy (TEM). Black arrows indicate the tight junction structures (b, d). Transepithelial electrical resistance (TEER) (e) and apparent permeability coefficient (Papp) of fluorescein isothiocyanate–dextran (FD) (f) were measured. Values are represented as means ± standard deviation (SD), ^# P < 0.05 and ^## P < 0.01 for comparison between the H and N groups, ^* P < 0.05 and ^** P < 0.01 for comparison between different time points in the H group