Objective To observe the temporal changes of hypoxia-inducible factor-1α( HIF-1α) in rat brain hippo-campus after acute hypobaric hypoxia and to explore the relationship between the changes and brain injury. Methods We randomly divided 100 male SD rats into the normoxic control group and hypoxia injury groups. The rats of hypoxia injury groups were further divided into four subgroups (6 h, 12 h, 18 h and 24 h) on the basis of the duration in hypobaric hy-poxia and 20 rats in each group. Except the control group, other four subgroups were placed in hypobaric chamber imitating a plateau of 7000 meters. After hypobaric hypoxia injury, the morphological changes of hippocampus were observed by HE staining. The brain water content, the level of NO and the activity of nitric oxide synthase ( NOS) were detected. The ex-pression of HIF-1α mRNA was detected by RT-PCR and HIF-1α mRNA protein was detected by immunofluorescence stai-ning. Results ①Compared with the control group, after hypobaric hypoxia, the neurocytes in the hippocampus showed varying degrees of swelling, necrosis, apoptosis and karyorrhexis or karyolysis. The cytoplasm was stained with inhomoge-neous oxyphilic red colour. The CA1 in hippocampus was more sensitive to hypobaric hypoxia than the others. ②Compared with control group, the brain water content was significantly increased in a time-dependent manner in the subgroups ( all P<0.01). ③Compared with the control group, the activities of NOS in each subgroup was increased (all P <0. 01). Meanwhile, except the 6 h group, the levels of NO in each subgroup was increased in a time-dependent manner ( all P<0. 01). ④The expression of HIF-1α mRNA was not detected in the control group. Compared with the control group, the expression of HIF-1α was significantly increased with a time-dependent manner in the subgroups (P<0. 01 or P<0. 05). The results of immunofluorescence showed no green fluorescence of HIF-1αprotein was found in hippocampus of the control group. After hypobaric hypoxia, a weak green fluorescence appeared in part of cytoplasm at first, but with prolonged hypox-ia time, a gradually enhanced fluorescence was observed and it showed a trend of aggregating to the nucleus. Conclusions Acute hypobaric hypoxia increased the brain water content and led to cerebral edema and the extent of damage was aggra-vated with prolonged hypoxia time. Stressful expression of HIF-1αplayed an important role in protective regulation of cere-bral injury induced by acute hypobaric hypoxia.%目的：观察急性低压缺氧大鼠脑组织海马区缺氧诱导因子1α( HIF-1α)表达的时序性变化,探讨其与缺氧性脑损伤的关系。方法将100只成年雄性SD大鼠随机分为常氧对照组、低压缺氧6 h组、低压缺氧12 h组、低压缺氧18 h组和低压缺氧24 h组,每组20只。各低压缺氧组置于低压氧舱模拟海拔7000 m高原环境。采用HE染色法观察各组脑组织海马区形态学改变,检测脑组织含水量,一氧化氮合酶( NOS)活性及NO含量,反转录聚合酶链反应( RT-PCR)检测HIF-1α mRNA,免疫荧光化学染色法定位HIF-1α蛋白。结果①与常氧对照组比较,各低压缺氧组脑组织海马区神经细胞均有不同程度的水肿、坏死或凋亡,细胞质不规则红染,核仁碎裂或消失,且海马各区损伤程度不同,以 CA1区最为严重；②与常氧对照组比较,各低压缺氧组脑组织含水量均显著上升(P均<0.01),且随缺氧时间的延长呈递增趋势；③与常氧对照组比较,各低压缺氧组脑组织NOS活性均显著升高(P均<0.01)；除低压缺氧6 h组外,其余各组脑组织NO含量均随缺氧时间的延长而显著增加(P均<0.01)；④常氧对照组中未检测到HIF-1αmRNA表达,各低压缺氧组HIF-1αmRNA相对表达均显著增加,且具有时间依赖性(P<0.01或<0.05)；常氧对照组脑组织海马各区均未见HIF-1α蛋白阳性标记的绿色荧光,低压缺氧损伤后先在部分神经细胞胞质中出现微弱荧光信号,随着缺氧时间的延长荧光强度逐渐增强,并明显呈向胞核聚集的趋势。结论急性低压缺氧可导致脑含水量升高,引发脑水肿,且损伤程度随缺氧时间的延长而加重；HIF-1α的应激性表达对急性低压缺氧性脑损伤有保护性调控作用。
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