Figure 4

Hyperoxia exposure disrupts alveolar epithelial tight junctions. The integrity of pulmonary epithelium and morphological alterations of tight junction were studied by transmission electron microscopy in both normoxia and hyperoxia groups. Tight junctions between pulmonary epithelial cells were extremely tight in the lungs from normoxia-treated newborn rats (A and B). After treatment with hyperoxia for 7 days, tight junctions were irregularly widened (C and D). Tight junctions were open between epithelial cells in newborn rats with hyperoxia for 5 days, and paracellular gaps were visible between alveolar epithelial cells (E and F). Intact tight junctions remained between alveolar epithelial cells in newborn rats exposed to hyperoxia for 1 and 3 days (G and H).