Ultrastructure Changes of Alveolar Epithelia Type II Cells in Newborn Rats with Chronic Lung Disease Induced by Hyperoxia

Objective To investigate the epithelial permeability in lung tissue and the ultrastructure dynamic changes of alveolar epithelia type Ⅱ cells(AEC Ⅱ) under hyperoxia-induced lung injury condition.Methods Three hundred and twenty cases of newborn rats were divided into 4 groups according to different oxygen concentrations(FiO2): experimental group 1(FiO2 800 mL·L-1),experimental group 2(FiO2 600 mL·L-1),experimental group 3(FiO2 400 mL·L-1) and room-air control group(FiO2 210 mL·L-1).Rats were killed on the 1st,3rd,5th,7th and 14th day after the onset of the experiment.The ultrastructures dynamic changes of AEC Ⅱ and alveolar barrier function through lanthanum nitrate tracing technology were observed.Lung wet/dry weight ratio(W/D) and protein content in bronchoalveolar lavage fluid(BALF) were examined.Results The lung W/D ratios in experimental groups were significantly higher than those in room-air control group on the 5th,7th and 14th day of hyperoxia exposure(Pa0.05).The protein contents of BALF in experimental groups were significantly higher than those in room-air control group(Pa0.05) and increased as the oxygen concentration elevated and exposure time prolonged.The ultrastructures of AEC Ⅱ changed dramatically with longer exposure duration and the permeability of lanthanum nitrate in experimental groups were much higher than those in room-air control group.Conclusions Increased epithelial permeability which occurred at the early stage of hyperoxia-induced lung injury can lead to pulmonary edema;the lung injury became worse with higher oxygen concentration and longer exposure duration.