中文摘要：

目的探讨高体积分数氧（高氧）暴露早产新生大鼠肺组织超微结构变化与氧化应激反应的关系。方法将160只新生SD大鼠（孕21d）随机分为空气组（Ⅰ组）、高氧组（Ⅱ组）、高氧加大剂量N-乙酰半胱氨酸（NAC）组（Ⅲ组）和高氧加小剂量NAC组（Ⅳ组），每组各40只。Ⅰ组在空气中饲养，Ⅱ、Ⅲ、Ⅳ组置于高氧箱（保持氧体积分数〉950mI／L）中饲养，Ⅲ、Ⅳ组大鼠以灌胃方式予NAC[Ⅲ组予NAC6．25×10^-2g／（kg·d），Ⅳ组剂量是Ⅲ组剂量的1／4，给药时间为出生第1-7天]。每组又随机分为第3、7、14、2l天4个亚组，每组各10只，分别在第3、7、14、2l天处死动物，收集其血浆和肺组织标本。采用ELISA方法检测各亚组大鼠血浆8-异前列腺素F2α（8-iso-PGF2α）水平，并应用透射电镜观察其肺组织超微结构改变。结果Ⅱ组第3天肺泡Ⅱ型上皮细胞（AEC Ⅱ）胞质中板层小体出现排空现象，AECⅠ、AECⅡ线粒体肿胀；肺组织中可见中性粒细胞浸润。第7天各种细胞超微结构改变较第3天更加明显，AECⅡ胞质中板层小体排空现象增加，各种细胞线粒体肿胀更加明显，呈气球样变；部分AECⅡ出现坏死；第14、2l天，AEC基底膜及气血屏障明显增厚；成纤维细胞增殖，肺问质可见大量胶原原纤维。Ⅲ组第3、7天时肺组织各类细胞线粒体肿胀明显减轻，AECⅡ板层小体排空明显减少，未见AECⅡ坏死或凋亡；第14、21天肺间质中胶原纤维未见明显增加。Ⅳ组肺组织超微结构在各时间点的变化较Ⅱ组稍减轻。Ⅱ组早产新生大鼠血浆8-iso-PGF2α水平从第3天即开始升高，第14天最高，第2l天虽较前明显下降，但仍显著高于Ⅰ组；Ⅲ组各时间点血浆8-iso-PGF2α水平较Ⅱ组明显降低，但仍高于Ⅰ组；Ⅳ组血浆8-iso-PGF2α水平较Ⅱ组降低不明显。结论高氧暴露诱导的肺损伤早期以AEC，尤其是AECⅡ损伤

英文摘要：

Objective To explore the relationship between lung ultrastructure and oxidative stress reaction in newborn premature rats exposed to hyperoxia. Methods One hundred and sixty premature newborn SD rats （gestational age = 21 d,） which delivered by cesarean section were randomly assigned into air group （group Ⅰ） , hyperoxia group （group Ⅱ） , hyperoxia and high -dose N-Acetylcysteine （NAC） group （ group Ⅲ ） and hyperoxia and low-dose NAC group （ group IV ） , 40 rats in each group. According to the time of hyperoxic exposure, each group was randomly divided into 4 subgroups：the third,7^th, 14^th and 21^th day group, l0 rats in every subgroup. Rats of group I were raised in room air while rats of other groups were raised in boxes with hyperxia （more than 950 mL/L,detected by oxygen monitor）. The rats in group Ⅲ were administered with NAC[6.25 × 10^-2g/（ kg·d）] by garage for 7 days, The dosage of NAC in group Ⅳ was a quarter of that in group Ⅲ. On the third, 7^th , 14^th and 21^th day of experiment, 10 rats from each subgroup were sacrificed after anesthesia. The plasma was collected and the lung tissue was separated and fixed. The plasma 8-iso-prosta-glandin F2α（8- iso-PGF2α） contents in rats of every subgroup were detected by ELISA and the ultrastructural changes of lung tissue were observed by transmission electron microscope. Results The lamellar bodies of alveolar epithelial cell Ⅱ （ AEC Ⅱ ） in group Ⅱ on the third day showed emptying phenomenon, the mitochondria of AEC Ⅰ and AEC Ⅱ were swollen and neutrophilic leukocytes infiltrated into lungs. The various changes of ultrastructure on the 7^th day were more obvious than those on the third day. The lamellar bodies of AEC Ⅱ had more emptying phenomena and mitochondria in every cell had heavier swelling, even ballooning degeneration. Some of AEC Ⅱ developed necrosis. On the 14^th day, the basement membrane of AEC and air-blood barrier became thickening and plenty of collagen fibril deposited in lu