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

在出生时，哺乳动物暴露于氧气张力从子宫内的低氧（PO2为12托）到大气环境中的高氧（PO2大于100托）。特别是肺上皮在呼吸开始时氧张力急剧增加。为了探索哺乳动物对氧张力变化的适应机制，本研究采用荧光差异显示的方法筛选了对氧张力变化有响应的基因。在不同氧浓度下培养胎鼠肺分离成纤维细胞和SV40永活2型肺泡上皮细胞。在暴露于缺氧前后从这些细胞中分离总RNA。用fitc标记的锚定引物和任意引物进行RT-PCR扩增后，用6% PAGE分离DNA片段，用Pharmacia Fragment Manager或放射自显影分析。4个DNA片段在缺氧条件下差异表达，其中3个片段序列与醛缩酶a、磷酸甘油酸突变酶B型亚基和脯氨酸4-羟化酶的3′端相同。最后一个DNA片段与数据库中任何基因均无同源性。脯氨酰4-羟化酶在缺氧条件下上调，在氧张力由缺氧向常氧转变时下调。此外，胎儿肺中的RNA比成人肺中的RNA更丰富。这些数据表明胶原蛋白代谢可能受氧张力调节。

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.