Objective    To investigate the effect of hyperoxia on type Ⅱ alveolar epithelial cells (AECⅡ) isolated from prematural rats and the protection of neuropeptide substance P (SP).      Methods    ① Prematural rats AECⅡ were isolated

purified and randomly divided into following groups

including air exposure group

hyperoxia exposure

group

SP treatment group. Oxygen capacity fraction was 21% in air group while 95% in hyperoxia group. SP treatment group was added 1×10

-6

mol/L SP before AECⅡ were exposed to 21% or 95% oxygen for 12

24 and 48 h respectively. Morphologic change of AECⅡ was observed under electron microscope. XTT and flow cytometry were employed to detect growth rate and apoptosis of AECⅡ. ② Prematural SD rats (full term is 22 d) of 21 days old were taken out by opening wombs and randomly divided into two groups: air exposure group (21% oxygen) and hyperoxia exposure group (95% oxygen). After 3

7

14 d of exposure

the levels of SP in lung tissues were determined.     Results    Compared to air exposure group

the growth rate of AECⅡ in hyperoxia exposure group decreased signficantly after 12

24 and 48 h of exposure. Nevertheless

significantly increased growth rate and decreased apoptosis rate of AECⅡ were observed after SP interference

and the morphological damage was also improved. SP of lung tissues decreased significantly in hyperoxia exposure group after 3

7 and 14 d of exposure

compared to air exposure group. Moreover

SP decreased more significantly with the extension of hyperoxia exposure.      Conclusion    SP could promote the proliferation and inhibit the apoptosis of AECⅡand maybe play a protective role for AECⅡ under hyperoxia condition. The content change of SP in lung tissues is possibly related to the injury and healing of AECⅡ exposed to hyperoxia.