SCRENING OF IN NEW-BORN RAT LUNG GENES RESPONDING TO OXYGEN TENSION SHIFT

在出生时，哺乳动物暴露于从子宫中的低O2（PO 2为12 Torr）到大气环境中的高O2（PO 2大于100 Torr）的氧张力变化。特别是，肺上皮细胞在呼吸开始时氧张力急剧增加。为了探讨哺乳动物对氧张力改变的适应机制，本研究采用荧光差异显示技术筛选了与氧张力改变相关的基因，并将胎鼠肺成纤维细胞和SV 40永生化的2型肺泡上皮细胞在不同氧张力下培养。在暴露于缺氧之前和之后从这些细胞中分离总RNA。用FITC标记的锚引物和随机引物进行RT-PCR扩增后，经6% PAGE电泳分离DNA片段，用Pharmacia Fragment Manager或放射自显影分析，得到4个缺氧差异表达的DNA片段，其中3个片段与醛缩酶a、磷酸甘油酸酯酶B型B亚基和脯氨酰4-羟化酶的3'端序列一致。脯氨酰4-羟化酶基因在缺氧条件下表达上调，在缺氧条件下表达下调。此外，RNA在胎儿肺中比在成人肺中更丰富。这些数据表明，胶原代谢可能是由氧张力调节。

At birth, mammals are exposed to oxygen tension shift from low O2 in the uterus (PO2 is 12 Torr) to high O2 in atmospheric environment (PO2 is more than 100 Torr). Especially, the lung epithelium receives drastic increase in oxygen tension at the beginning of respiration. In this study, we screened the genes which respond to oxygen tension shift using the fluorescent differential display method in order to explore the adaptation mechanism of mammals to oxygen tension shift.Fibroblast isolated from fetal rat lung and SV40 immortalized type 2 alveolar epithelial cell were cultured at various oxygen tension. Total RNA was isolated from these cells before and after exposures to hypoxia. After RT-PCR amplification with FITC-labeled anchor primers and arbitrary primers, DNA fragments were separated by 6% PAGE and analyzed by Pharmacia Fragment Manager or autoradiography.Four DNA fragments were differentially expressed by hypoxia and three of them have the sequence identical to 3' end of aldolase a, phosphoglycerate mutase type B subunit and prolyl 4-hydroxylase. The last DNA fragment showed no homology to any genes in data bank.Prolyl 4-hydroxylase was up-regulated by hypoxia and down-regulated by oxygen tension shift from hypoxia to normoxia. Furthermore, the RNA was more abundant in the fetal lung than in the adult lung. These data suggest that collagen metabolism may be regulated by oxygen tension.