内源性一氧化氮对大鼠慢性缺氧性肺动脉高压的调节作用

目的探讨一氧化氮对慢性缺氧性肺动脉高压的调节作用。方法采用Ｗｉｓｔａｒ大鼠１８只，随机将各配伍组大鼠分别分配到组Ⅰ（对照组）、组Ⅱ（缺氧组）及组Ⅲ［缺氧加一氧化氮合酶抑制剂Ｎω－硝基－Ｌ－精氨酸甲酯（Ｌ－ＮＡＭＥ组）］。研究Ｌ－ＮＡＭＥ对缺氧性肺动脉高压的影响。结果与对照组相比，缺氧加Ｌ－ＮＡＭＥ注射的大鼠肺动脉平均压上升百分数（５８％±１２％）明显高于单纯缺氧大鼠（３４％±１５％）（ｔ＝３．０１３，Ｐ＜０．０１）；缺氧加Ｌ－ＮＡＭＥ注射大鼠血浆一氧化氮下降百分数（３８％±４％）明显大于单纯缺氧大鼠（１２％±１２％）（ｔ＝２７；０．０５＞Ｐ＞０．０２）。结论大鼠慢性缺氧时一氧化氮释放减少，而一氧化氮释放减少可能参与缺氧性肺动脉高压的形成     

左旋硝基精氨酸对新生大鼠缺氧缺血性脑病的防治作用

本研究通过观察一氧化氮合成酶（ＮＯＳ）抑制剂左旋硝基精氨酸（ＬＮＮＡ）对新生大鼠缺氧缺血性脑病（ＨＩＥ）脑组织病理学及钙、水含量的影响来探讨其对ＨＩＥ的防治效果。对象和方法：１选７日龄Ｗｉｓｔａｒ大鼠１８只,雌雄不限,体重（１８±４）ｇ,由山西医...     

新生儿低氧性肺动脉高压的发病机制研究

新生儿低氧性肺动脉高压较为常见且病死率较高.其发病机制与肺动脉内皮功能障碍和(或)平滑肌细胞表型改变、功能障碍有关.急性缺氧时,肺动脉内皮一氧化氮合酶下调,一氧化氮合成减少,平滑肌细胞对一氧化氮的敏感性下降;内皮素生成增加,内皮素a受体基因表达增加,平滑肌表面分布密度增加;一氧化氮-内皮素-1轴失衡,使出生后肺动脉舒张过程受损,血管紧张度增高.低氧查影响新生儿血管平滑肌细胞表型转变为合成表型优势,与低氧发牛时机密切相关;缺氧状态持续影响了氧敏感基因转录因子的活性,进一步导致肺动脉平滑肌细胞增殖肥大,血管壁结构重建,加重肺动脉高压.内皮与平滑肌细胞之间也通过相互作用影响各自功能.因此,了解其发生机制,对探讨新生儿肺动脉高压的治疗措施有重要意义.     

内皮素与新生儿败血性休克的研究

为了探讨内皮素在新生儿败血性休克中的作用，应用体外培养及放射免疫测定法，观察内毒素对人脐静脉血内皮细胞分泌内皮素的影响及山莨菪碱（６５４－２）的可能作用，并测定３２例败血症及２１例败血性休克新生儿血浆内皮素含量的变化。结果：（１）内毒素能刺激人脐静脉内皮细胞内皮素的分泌，呈时间及剂量依赖性；（２）６５４－２在体外能抑制内毒素刺激的内皮素的合成；（３）新生儿败血症及败血性休克时血浆内皮素水平明显增高，并与疾病严重程度及预后有关。提示：内皮素参与新生儿败血性休克的病理生理过程，为６５４－２治疗败血性休克提供了新的理论依据。     

一氧化氮合酶mRNA在缺氧性肺动脉高压大鼠肺动脉的表达

目的探讨一氧化氮体系在缺氧性肺动脉高压形成机制中的作用。方法采用地高辛精标记的一氧化氮合酶（ＮＯＳ）ｃＲＮＡ探针对缺氧组大鼠（６只）及对照组大鼠（７只）进行原位杂交。结果缺氧２周后的大鼠肺动脉收缩压（３．８±０．７ｋＰａ）（２８±５ｍｍＨｇ，１ｋＰａ＝７．５ｍｍＨｇ）、肺动脉平均压（２．８±０．６ｋＰａ）及肺动脉舒张压（１．４±０．４ｋＰａ）与对照组（２．９±０．５ｋＰａ，１．９±０．５ｋＰａ及０．９±０．５ｋＰａ）相比均显著升高。缺氧组大鼠肺动脉内皮细胞中ＮＯＳｍＲＮＡ表达信号为弱阳性（３只）及阴性（３只），平滑肌细胞中表达信号均为阴性；对照组大鼠肺动脉内皮细胞中ＮＯＳｍＲＮＡ表达信号为阳性（７只），平滑肌细胞中表达信号均为阴性。ＮＯＳｍＲＮＡ的表达强度与大鼠肺动脉收缩压、肺动脉平均压及肺动脉舒张压分别呈负相关（ｒｓ＝－０．６７３、－０．５９６及－０．６２１，Ｐ均＜０．０５）。结论缺氧时肺动脉内皮细胞ＮＯＳｍＲＮＡ表达的改变可能参与慢性缺氧性肺动脉高压的形成。     

氨基胍和L-硝基-精氨酸甲酯对新生大鼠缺氧缺血性脑损伤神经元凋亡的影响

神经细胞凋亡在缺氧缺血性脑病（HIE)迟发性损伤中占重要地全^[1,2]，因此通过抗凋亡治疗以抑制或减轻神经元的迟发性扣内务 可能成为治疗缺氧血性脑损伤（ＨＩＢＤ）的重要途径之一，我们采用氨基胍（ＡＧ）和Ｌ－硝基－精氨酸甲酯（Ｌ－ＮＡＭＥ），对ＨＩＢＤ大鼠进行干预，探讨其对凋亡的影响。     

一氧化氮对缺氧性肺血管结构重建大鼠肺动脉血小板源生长因子表达的影响

目的 探讨一氧化氮对缺氧性肺血管结构重建大鼠肺动脉中血小板源生长因子 （ＰＤＧＦ）表达的影响。方法 将大鼠随机分为４组：常氧组（６只）、低氧组（６只）、低氧＋Ｌ－精氨酸组（低氧＋Ｌ－Ａｒｇ组）（７只）及低氧＋Ｎ＾ω－硝基－Ｌ－精氨酸甲酯组（低氧＋Ｌ－ＮＡＭＥ组）（６只）。以光学显微镜观测４组大鼠肺中、小肌型动脉的相对中膜厚度（ＲＭＴ）。应用ＰＤＧＦ的单克隆抗体经免疫组织化学技术对４组大鼠肺动脉ＰＤ     

内皮素与肺动脉高压

内皮素（ＥＴ）是从内皮细胞提取出来的一种血管活性肽，具有广泛的生物学作用，对许多疾病的发生有重要意义。近年来，发现肺动脉高压时血浆及肺内猪内皮素（ＥＴ－１）水平明显升高，提示ＥＴ－１在肺动脉高压的病理过程中可能起着重要作用，本文综述了ＥＴ－１在肺动脉高压的病理生理中的作用及有关进展。     

缺氧缺血性脑病新生儿血浆与脑脊液中内皮素及内源性类洋地黄素的变化及意义

为了探讨内皮素１（ＥＴ１）及内源性类洋地黄素（ＥＤＬＦ）在新生儿缺氧缺血性脑病（ＨＩＥ）中的作用及意义，作者测定了ＨＩＥ新生儿血浆及脑脊液（ＣＳＦ）中ＥＴ１与ＥＤＬＦ的水平。对象：（１）病例组：共４５例，男３１，女１４。诊断依据为１９８９年济南...     

缺氧缺血性脑病新生鼠中枢神经系统一氧化氮合酶的变化

一氧化氮合酶（ＮＯＳ）催化Ｌ精氨酸分解生成一氧化氮（ＮＯ）和瓜氨酸,ＮＯＳ活性的变化反映组织内ＮＯ含量的变化。ＮＯ是一种具有广泛生理活性的物质,除血管内皮细胞、巨噬细胞等能合成内源性ＮＯ外、脑组织也是内源性ＮＯ合成的重要场所。本研究缺氧缺血性脑病（ＨＩＥ）新生鼠中枢神经系统中ＮＯＳ的变化,以探讨脑组织局部ＮＯ的变化。材料和方法：１－实验动物：正常７日龄、体重１８～２２ｇ的ＳＤ新生鼠４５只,随机分成三组,每组１５只：正常对照组;急性缺氧组：吸入氧浓度（ＦｉＯ２）为０－０８的氧１０～１５分钟;ＨＩ…     

Acute normoxia increases fetal pulmonary artery endothelial cell cytosolic Ca2+ via Ca2+-induced Ca2+ release

To test the hypothesis that an acute increase in O(2) tension increases cytosolic calcium ([Ca(2+)](i)) in fetal pulmonary artery endothelial cells (PAECs) via entry of extracellular calcium and subsequent calcium-induced calcium release (CICR) and nitric oxide release, low-passage PAECs (<10 passages) were isolated from the intralobar pulmonary artery (PA) of fetal sheep and maintained under hypoxic conditions (Po(2), 25 Torr). Using the calcium-sensitive dye fura-2, we demonstrated that acute normoxia (Po(2) = 120 Torr) increased PAECs [Ca(2+)](i) by increasing the rate of entry of extracellular calcium. In the presence of either ryanodine or 2-aminoethoxy-diphenylborate (2APB), normoxia did not lead to a sustained increase in PAECs [Ca(2+)](i) Whole-cell patch clamp studies demonstrated that acute normoxia causes PAEC membrane depolarization. When loaded with the nitric oxide (NO)-sensitive dye, DAF - FM, acute normoxia increased PAEC fluorescence. In PAECs derived from fetal lambs with pulmonary hypertension, an acute increase in O(2) tension had no effect on either [Ca(2+)](i) or NO production. Hypoxia increases loading of acetylcholine-sensitive calcium stores, as hypoxia potentiated the response to acetylcholine We conclude that acute normoxia increases [Ca(2+)](i) and NO production in normotensive but not hypertensive fetal PAECs via extracellular calcium entry and calcium release from calcium-sensitive intracellular stores.     

L—精氨酸和卡托普利对内皮细胞释放NO及ET—1的影响

为了解比较Ｌ－精氨酸和卡托普利对骨皮细胞释放骨皮衍化因子的影响，本实验采用比色法和放射免疫法测定血管紧张素Ⅱ刺激后的血管内皮培养液中ＮＯ和ＥＴ－１水平，结果显示Ｌ－Ａｒｇ和Ｃａｐｔｏｐｒｉｌ增加内皮细胞释放ＮＯ、抵制ＥＴ－１分泌，后效果虽效Ｌ－Ａｒｇ弱，但仍是一种可以通过Ｌ－Ａｒｇ－ＮＯ途径发挥药理作用的血管扩张剂。     

Effects of hypoxia-ischemia and inhibition of nitric oxide synthase on cerebral energy metabolism in newborn piglets.

The present study was designed to examine the effects of inhibition of nitric oxide synthase on cerebral energy metabolism after hypoxia-ischemia in newborn piglets. Ten 1- to 3-d-old piglets received N(omega)-nitro-L-arginine (NNLA), an inhibitor of nitric oxide synthase (NNLA-hypoxia, n = 5), or normal saline (hypoxia, n = 5) 1 h before cerebral hypoxia-ischemia. After the infusion, hypoxia-ischemia was induced by bilateral occlusion of the carotid arteries and decreasing FiO2 to 0.07 and maintained for 60 min. Thereafter, animals were resuscitated and ventilated for another 3 h. Using 1H- and 31P-magnetic resonance spectroscopy, cerebral energy metabolism was measured in vivo at 15-min intervals throughout the experiment. Phosphocreatine to inorganic phosphate ratios decreased from 2.74 +/- 0.14 to 0.74 +/- 0.36 (hypoxia group) and 2.32 +/- 0.17 to 0.18 +/- 0.10 (NNLA-hypoxia group) during hypoxia-ischemia. Thereafter, phosphocreatine to inorganic phosphate ratios returned rapidly to baseline values in the hypoxia group, but remained below baseline values in the NNLA-hypoxia group. Intracellular pH decreased during hypoxia-ischemia and returned to baseline values on reperfusion in both groups. Intracellular pH values were lower in the NNLA-hypoxia group (p < 0.001, ANOVA). Lactate was not present during the baseline period. After hypoxia-ischemia, lactate to N-acetylaspartate ratios increased to 1.34 +/- 0.28 (hypoxia group) and 2.22 +/- 0.46 (NNLA-hypoxia group). Lactate had disappeared after 3 h of reperfusion in the hypoxia group, whereas lactate to N-acetylaspartate ratios were 1.37 +/- 1.37 in the NNLA-hypoxia group. ANOVA demonstrated a significant effect of NNLA on lactate to N-acetylaspartate ratios (p < 0.001). Inhibition of nitric oxide synthase by NNLA tended to compromise cerebral energy status during and after cerebral hypoxia-ischemia in newborn piglets.     

Effects of hypoxia on stress proteins in the piglet brain at birth

Newborn piglets were submitted to normobaric hypoxia (5% O2, 95% N2) for either 1 or 4 h. The effects of hypoxia on the neonatal brain were characterized through a time-course analysis of levels of various proteins such as heat shock proteins (HSP27, 70, and 90), hypoxia inducible factor-1alpha (HIF-1alpha), neuronal nitric oxide synthase (nNOS), hemeoxygenase-2 (HO-2), and caspase-3. The expression of these proteins was determined at different stages of recovery up to 72 h in cerebellum, cortex, and hippocampus by Western blot analysis in hypoxic maintained animals that were made hypoxic at either 20 or 37 degrees C. In all regions of the brain, HIF-1alpha and HSP27 expression were strongly increased until 22 h of recovery. No significant changes were observed for HSP70, HSP90, and HO-2. A small elevation of expression of nNOS was observed at early stages in the cerebellum and the cortex with no change in the hippocampus. Expression of caspase 3 was strongly increased in the cortex 24 and 48 h after hypoxia but unchanged in the hippocampus. These results are presented in terms of the porcine model of nonischemic hypoxia and its delayed neuronal effects on the cerebral outcome. Because of their recently established biochemical and functional interactions, the expression of the main HSPs, HIF-1alpha, nNOS, and caspase-3 after hypoxia are delineated.     

不同干预方法对实验性肥胖大鼠早期血管内皮功能障碍作用的比较

目的 观察单纯控制食谱、控制食谱联合有氧运动或降脂药对实验性肥胖大鼠血脂和血管内皮功能的影响。方法 Wistar大鼠随机分为：F组：饲予高脂饲料;N组：饲予基础饲料;A组：高脂饲养8周后予单纯控制食谱12周,B组：高脂饲养8周后予控制食谱联合游泳12周,C组：高脂饲养8周后予控制食谱联合藻酸双酯钠12周。干预12周后,处死全部大鼠,测定Lee指数;血脂指标：总胆固醇（TC）、甘油三酯（TG）;血管内皮因子：血浆内皮素（ET）、血清一氧化氮（NO）,血浆血管性假血友病因子（vWF）,免疫组化法检测腹主动脉细胞间黏附分子1（ICAM-1）蛋白的表达,逆转录-聚合酶链反应（RT-PCR）法检测腹主动脉ICAM-1mRNA的表达。结果 A组的TC、TG、ET低于F组（均P〈0．05）;B、C组的Lee指数、TC、TG、ET、vWF、ICAM-1蛋白和mRNA表达水平均低于F组（均P〈0．05）;A、C两组NO均高于F组（均P〈0．05）,与N组比较差异无统计学意义（均P〉0、05）,B组NO同时高于F组和N组（P〈0．01）。结论 单纯控制食谱能改善血脂和血管舒缩功能,控制食谱联合有氧运动或联合降脂药藻酸双酯钠在减重、降脂和改善血管舒缩、凝血、黏附功能方面均有效,而控制食谱联合有氧运动改善舒缩功能的效果更为显著,因此是单纯肥胖早期血管内皮功能障碍的最佳干预选择。     

Role of endothelins and nitric oxide in the pulmonary circulation of perinatal lambs during hyperoxia and hypoxia

Endothelins (ET) have opposite vascular effects mediated through different receptors: ET(A) receptors mediating vasoconstriction and ET(B) receptors mediating vasoconstriction as well as vasodilation. The role of ET in acute hypoxic pulmonary vasoconstriction (HPV) was studied after dual ET receptor blockade with bosentan and nitric oxide (NO) synthase inhibition with nitro-L-arginine (L-NA). We started from the hypothesis that ET antagonism may inhibit HPV but, if not, would do so after NO synthase inhibition. HPV was evaluated in anesthetized lambs, with an intact pulmonary circulation, by the increase in the mean pulmonary artery pressure (Ppa) minus occluded Ppa (Ppao) gradient in response to hypoxia (inspiratory oxygen fraction of 0.1) at different levels of pulmonary flow (multipoint pressure/flow relationships). ET receptor antagonism decreased pulmonary and systemic vascular tone both in hyperoxia and hypoxia. ET antagonism had no effect on HPV. NO synthase inhibition increased pulmonary vascular tone more in hypoxia than in hyperoxia so that HPV was enhanced. After L-NA, bosentan still decreased pulmonary vascular tone in hypoxia but did not affect the magnitude of HPV. The present results suggest that ET and NO are involved in the regulation of basal pulmonary vascular tone. Furthermore, the vasodilator effect of bosentan persisted in the presence of NO synthase inhibition, suggesting a non NO-dependent vasodilator mechanism. The results from these experiments are in agreement with the idea that ET do not play a major role in HPV in the perinatal lamb, even when it is enhanced by NO synthase inhibition.     

Betamethasone attenuates oxidant stress in endothelial cells from fetal lambs with persistent pulmonary hypertension

We investigated the effects of betamethasone on oxidative stress and impaired vasodilation in a lamb model of persistent pulmonary hypertension (PPHN). We treated pregnant ewes following fetal ductal ligation with betamethasone or saline for 48 h before delivery. Response of fetal pulmonary arteries to nitric oxide synthase (NOS) agonist adenosine triphosphate (ATP) and nitric oxide (NO) donor, s-nitroso-n-acetyl-penicillamine (SNAP) was determined in tissue bath. Pulmonary artery endothelial cells (PAEC) from fetal lambs with ductal ligation or sham ligation were treated with betamethasone or its vehicle for 48 h. Expression of endothelial NOS (eNOS), endothelin, endothelin-B (ET-B) receptor, and CuZn- and Mn-superoxide dismutase (SOD) in PAEC was studied. Intracellular cGMP and superoxide levels and interaction of eNOS with heat shock protein 90 (Hsp90) were determined in PAEC. Antenatal betamethasone improved the relaxation response of pulmonary arteries to ATP and SNAP in PPHN. PPHN was associated with decreases in eNOS and ET-B receptor and increase in prepro-endothelin mRNA levels. Betamethasone decreased prepro-endothelin mRNA and ET-1 pro-peptide levels and increased eNOS and MnSOD protein levels in PPHN. Betamethasone reversed the increased superoxide/decreased cGMP levels and restored Hsp90-eNOS interactions in PPHN. Betamethasone reduces oxidative stress and improves response of pulmonary arteries to vasodilators in lambs with PPHN.     

缺氧缺血新生大鼠神经元自噬基因表达节律及调控机制

目的通过新生大鼠缺氧缺血脑损伤后神经元自噬基因和节律基因的表达,探讨缺氧缺血引起神经损伤的新机制。方法将12只Sprague-Dawley大鼠随机分为缺氧缺血组和假手术组,每组6只。采用结扎并切断大鼠右侧颈总动脉并给予低氧处理的方法建立体内缺氧缺血脑损伤模型。Western blot检测两组大鼠大脑皮层和海马组织节律蛋白Clock表达情况。体外培养大鼠神经元细胞,随机分为氧糖剥夺(OGD)组和对照组,OGD组加入无糖无血清DMEM培养基模拟细胞缺血状态,并给予低氧处理建立体外缺氧缺血脑损伤模型。采用Western blot检测两组不同时间点自噬相关蛋白Beclin1和LC3,以及节律基因Clock蛋白表达情况。应用si RNA技术抑制神经元Clock蛋白表达后,检测Beclin1和LC3的表达变化。结果体外培养神经元Beclin1和LC3Ⅱ的表达呈现节律性波动;OGD处理后,体外培养神经元Beclin1和LC3Ⅱ的表达随着时间的延长逐渐升高,不再呈现节律性波动;与假手术组相比,缺氧缺血引起大鼠皮层和海马组织Clock表达降低(P0.05);体外培养神经元经OGD处理后,Clock表达也较对照组显著降低(P0.05);与阴性对照组相比,抑制神经元节律基因Clock表达后,自噬相关蛋白Beclin1和LC3Ⅱ的表达均显著下降(P0.05)。结论缺氧缺血引起神经元Beclin1和LC3Ⅱ表达节律紊乱,其机制可能与Clock参与调控Beclin1和LC3Ⅱ的表达有关。     

Asymmetric dimethyl arginine and symmetric dimethyl arginine levels in infants with persistent pulmonary hypertension of the newborn.

OBJECTIVE: We investigated whether infants with persistent pulmonary hypertension had elevated levels of asymmetric dimethyl arginine, an endogenous inhibitor of nitric oxide synthase, and symmetric dimethyl arginine, a regioisomer. DESIGN: Prospective observational cohort study. SETTING: A 10-bed neonatal intensive care unit in a tertiary referral center. PATIENTS: Forty five infants >34 wks gestation and <2 wks old admitted to our intensive care unit. INTERVENTIONS: Samples of urine on days 1, 3, and 5 were analyzed by high-performance liquid chromatography to determine asymmetric dimethyl arginine and symmetric dimethyl arginine levels. The clinical progression and treatment of the infants were noted. MEASUREMENTS AND MAIN RESULTS: Twenty-nine infants had a clinical diagnosis of persistent pulmonary hypertension confirmed on echocardiography, and there were 16 control infants. Median asymmetric dimethyl arginine levels on day 1 were significantly higher in the persistent pulmonary hypertension group (n = 29), 14.8 (10.3-21.7) mmol.mmol creatinine(-1).L(-1), compared with controls (n = 16), 3.6 (1.4-5.2) mmol.mmol creatinine(-1).L(-1) (p < .001). Asymmetric dimethyl arginine levels decreased to control levels by day 5 (p = .33). Symmetric dimethyl arginine levels were significantly higher than controls on day 1, 31.0 (21.7-65.9) vs. 14.7 (4.1-20.2) mmol.mmol creatinine(-1).L(-1) (p = .001) and day 3, 34.7(20.3-42.5) mmol.mmol creatinine(-1).L(-1) (p = .0001) and by day 5 had decreased significantly (p = .007) back to 16.7 (12.3-23.8) mmol.mmol creatinine(-1).L(-1), which was not significantly different than the control group values. CONCLUSIONS: These results support the hypothesis that asymmetric dimethyl arginine and symmetric dimethyl arginine levels are elevated in patients with persistent pulmonary hypertension. Thus, endogenous inhibition of nitric oxide synthase by asymmetric dimethyl arginine may be responsible for the development of persistent pulmonary hypertension, suggesting novel therapeutic options in persistent pulmonary hypertension.     

苦参碱和川芎嗪抑制白血病细胞侵袭转移作用的实验研究

目的探讨苦参碱及川芎嗪对低氧(3%O2)培养条件下人B淋巴细胞白血病细胞株Raji细胞、人慢性髓系白血病细胞株K562细胞侵袭转移的抑制作用及机制。方法体外常规培养细胞,低氧环境下继续培养24 h后,分别加入终浓度为0、0.15、0.2、0.25 g/L苦参碱或0、0.1、0.15、0.2 g/L川芎嗪处理,以常氧培养不加药物的细胞为对照组,分别检测细胞黏附、迁移和侵袭能力,并以RT-PCR方法检测HIF-1α、VEGF mRNA的表达。结果低氧环境下Raji细胞和K562细胞的黏附、迁移和侵袭能力,以及HIF-1α、VEGF mRNA的表达均较常氧对照组显著增强(P<0.01)。0.15、0.2、0.25 g/L苦参碱均有效抑制低氧环境下Raji细胞的黏附、迁移和侵袭能力,并下调HIF-1α、VEGF mRNA的表达(P<0.05)。0.2、0.25 g/L苦参碱均有效抑制低氧环境下K562细胞的黏附、迁移和侵袭能力并下调HIF-1α、VEGF mRNA的表达(P<0.05)。0.1、0.15、0.2 g/L川芎嗪均有效抑制Raji细胞、K562细胞的黏附、迁移和侵袭能力,并下调HIF-1α、VEGF mRNA的表达(P<0.05),均呈剂量依赖性。结论苦参碱和川芎嗪能有效抑制低氧环境下Raji细胞和K562细胞黏附、迁移和侵袭能力,其作用机制可能通过下调细胞内HIF-1αmRNA的表达,从而减少VEGF mRNA的生成来实现。