离子通道在肺动脉的分布及在低氧肺血管收缩反应中的作用

低氧性肺血管收缩反应（HPV）是指在急性低氧时,肺泡氧分压降到某一临界值,肺血管发生的快速、可逆的收缩反应,以纠正肺泡通气／灌流的不匹配。HPV的发生与肺动脉平滑肌细胞上K^＋、Ca^2＋、Cl^-通道的状态密切相关,而这些通道在不同部位的肺动脉上分布存在差异,因此不同部位的肺动脉在低氧中所表现的收缩反应程度也不同,本综述将对上述通道在肺动脉上的分布特点及其在HPV中的作用做一总结。     

尼氟灭酸在大鼠低氧高二氧化碳性肺血管收缩中的作用

目的：探讨氯离子通道阻断剂一尼氟灭酸（NFA）在大鼠低氧高二氧化碳性肺血管收缩（HHPV）中的作用。方法：采用大鼠HHPV模型,二、三级动脉环分别随机分4组（n=8）：常氧组（N组）、低氧高二氧化碳组（H组）、DMSO组（HD组）、尼氟灭酸组（NFA组）。在急性低氧高二氧化碳介质中,采用NFA分别孵育肺二、三级肺动脉环,按照低氧高二氧化碳反应性测定的方法测定其二、三级肺动脉血管环张力的变化,并观察NFA对HHPV的影响。结果：①H组二、三级肺动脉均呈现双向性收缩变化（I期快速收缩、快速舒张;II期持续性收缩）与N组相比有显著性差异（P〈0．05,P〈0．01）;②NFA组二、三级肺动脉环的低氧高二氧化碳性血管收缩作用明显减弱,尤其是Ⅱ期的持续收缩,与HD组相比有显著性差异（P〈0．05,P〈0．01）。结论：氯离子通道阻断剂一尼氟灭酸可减轻大鼠二、三级肺动脉环的张力变化率（尤其是Ⅱ期的持续性收缩）,从而发挥拮抗HHPV的作用。     

一氧化碳在低氧性肺血管收缩反应中的作用

目的和方法 :观察外源性一氧化碳 (CO)对大鼠离体肺动脉环低氧性收缩反应 (HPV)的影响 ,并通过观察血红素氧化酶抑制剂ZnPPIX对HPV的影响 ,探讨内源性一氧化碳在HPV中的作用及机制。结果 :低氧可使苯肾上腺素 (PE)预收缩的肺动脉环出现明显的收缩反应 ,肺动脉cGMP含量下降 ;用ZnPPIX孵育后 ,低氧后的肺动脉cGMP含量增加 ,低氧性肺血管收缩反应 (HPV)受抑 ;外源性CO可明显增加肺动脉cGMP含量 ,HPV明显受抑。结论 :外源性CO及ZnPPIX可增加低氧后的肺动脉cGMP含量 ,抑制HPV ,内源性CO减少导致cGMP含量下降可能是HPV的原因之一     

大鼠肺动脉平滑肌细胞钙激活氯通道电流的电生理检测

目的：研究大鼠肺动脉平滑肌细胞钙激活氯通道电流的电生理特性。方法：膜片钳全细胞和膜内向外记录模式检测大鼠肺动脉平滑肌细胞上钙激活氯通道全细胞电流和单通道电流。结果：大鼠肺动脉平滑肌细胞记录到稳定的钙激活氯通道电流（ICl（Ca））;ICl（Ca）表现出典型的外向整流特性和电压时间依赖性激活。结论：大鼠肺动脉平滑肌细胞膜上存在电压、时间依赖性氯通道电流,钙激活氯通道通过促进肺动脉平滑肌细胞去极化而成为调节肺动脉特性的关键调节因子。     

Effects of hypercapnia and NO synthase inhibition in sustained hypoxic pulmonary vasoconstriction

Background

Acute respiratory disorders may lead to sustained alveolar hypoxia with hypercapnia resulting in impaired pulmonary gas exchange. Hypoxic pulmonary vasoconstriction (HPV) optimizes gas exchange during local acute (0-30 min), as well as sustained (> 30 min) hypoxia by matching blood perfusion to alveolar ventilation. Hypercapnia with acidosis improves pulmonary gas exchange in repetitive conditions of acute hypoxia by potentiating HPV and preventing pulmonary endothelial dysfunction. This study investigated, if the beneficial effects of hypercapnia with acidosis are preserved during sustained hypoxia as it occurs, e.g in permissive hypercapnic ventilation in intensive care units. Furthermore, the effects of NO synthase inhibitors under such conditions were examined.

Method

We employed isolated perfused and ventilated rabbit lungs to determine the influence of hypercapnia with or without acidosis (pH corrected with sodium bicarbonate), and inhibitors of endothelial as well as inducible NO synthase on acute or sustained HPV (180 min) and endothelial permeability.

Results

In hypercapnic acidosis, HPV was intensified in sustained hypoxia, in contrast to hypercapnia without acidosis when HPV was amplified during both phases. L-N^G-Nitroarginine (L-NNA), a non-selective NO synthase inhibitor, enhanced acute as well as sustained HPV under all conditions, however, the amplification of sustained HPV induced by hypercapnia with or without acidosis compared to normocapnia disappeared. In contrast 1400 W, a selective inhibitor of inducible NO synthase (iNOS), decreased HPV in normocapnia and hypercapnia without acidosis at late time points of sustained HPV and selectively reversed the amplification of sustained HPV during hypercapnia without acidosis. Hypoxic hypercapnia without acidosis increased capillary filtration coefficient (Kfc). This increase disappeared after administration of 1400 W.

Conclusion

Hypercapnia with and without acidosis increased HPV during conditions of sustained hypoxia. The increase of sustained HPV and endothelial permeability in hypoxic hypercapnia without acidosis was iNOS dependent.     

Free radical production in hypoxic pulmonary artery smooth muscle cells

This study used an inexpensive and versatile environmental exposure system to test the hypothesis that hypoxia promoted free radical production in primary cultures of rat main pulmonary artery smooth muscle cells (PASMCs). Production of reactive species was detected by fluorescence microscopy with the probe 2', 7'-dichlorodihydrofluorescein, which is converted to the fluorescent dichlorofluorescein (DCF) in the presence of various oxidants. Flushing the airspace above the PASMC cultures with normoxic gas (20% O(2), 75% N(2), and 5% CO(2)) resulted in stable PO(2) values of approximately 150 Torr, whereas perfusion of the airspace with hypoxic gas (0% O(2), 95% N(2), and 5% CO(2) ) was associated with a reduction in PO(2) values to stable levels of approximately 25 Torr. Hypoxic PASMCs became increasingly fluorescent at approximately 500% above the normoxic baseline after 60 min. Hypoxia-induced DCF fluorescence was attenuated by the addition of the antioxidants dimethylthiourea and catalase. These findings show that PASMCs acutely exposed to hypoxia exhibit a marked increase in intracellular DCF fluorescence, suggestive of reactive oxygen or nitrogen species production.     

常氧和急性低氧下大鼠传导性肺动脉平滑肌细胞的电生理特性

本文旨在研究大鼠传导性肺动脉平滑肌细胞（pulmonary artery smooth muscle cells,PASMCs）的电生理特征及对急性低氧的反应。用酶解法急性分离出1-2级分支的PASMCs,通过全细胞膜片钳方法研究常氧及急性低氧状况下细胞钾电流的差异,并在常氧下先后使用iBTX和4-AP阻断大电导钙激活钾离子（large conductance Ca-activated K^＋,BKCa）通道及延迟整流性钾离子（delayed rectifier K^＋,KDR）通道后,观察细胞钾电流特征。根据细胞的大小、形态及电生理特征可将PASMCs分为Ⅰ、Ⅱ、Ⅲ类。iBTX对Ⅰ类细胞几乎无作用,而4-AP几乎完全阻断它的钾电流;Ⅱ类细胞的钾电流在加入iBTX后大部分被抑制,其余的对4．AP敏感;Ⅲ类细胞的钾电流对iBTX及4-AP均敏感。急性低氧对三类细胞的钾电流均有不同程度的抑制,并使Ⅰ类细胞的膜电位显著升高,而Ⅱ、Ⅲ类细胞膜电位升高的程度不如Ⅰ类显著。结果表明,传导性肺动脉有3种形态及电生理特性不同的PASMCs,在急性低氧时其钾电流不同程度地受到抑制,同时静息膜电位也有不同程度去极化,这些可能参与急性低氧时传导性肺动脉舒缩反应的调节。KDR及BKCa通道在3种细胞中的比例不同可能是急性低氧对3种PASMCs影响不同的离子基础。     

增殖细胞核抗原在低氧大鼠肺动脉平滑肌细胞中表达

目的通过建立低氧性肺动脉高压大鼠模型,探讨增殖细胞核抗原(proliferating cell nuclear antigen,PCNA)在大鼠低氧性肺血管平滑肌细胞中的表达。方法将SPF级SD大鼠随机分为正常对照组(n=10)、模型组(n=10),通过间断常压低氧法建立大鼠低氧性肺动脉高压模型,肺组织切片经HE染色后图像分析技术定量检测大鼠肺小动脉的形态改变;免疫组织化学染色法测定肺血管平滑肌细胞内PCNA蛋白表达,并经图像分析半定量检测其表达强度。结果 4周后,模型组SD大鼠MT%、MA%与对照组比较,差异具有显著性(P<0.05);模型组SD大鼠肺血管平滑肌细胞内PCNA核蛋白表达(积分面积、累积光密度)与对照组比较,差异具有显著性(P<0.05)。结论常压低氧4周可成功建立肺动脉高压大鼠模型,PCNA在肺血管平滑肌细胞中的表达量具有差异性提示其可能在肺动脉高压形成过程中起重要作用。     

Effect of L-arginine on pulmonary artery smooth muscle cell apoptosis in rats with hypoxic pulmonary vascular structural remodeling

This study investigated the effect of L-arginine (L-Arg) on the apoptosis of pulmonary arterysmooth muscle cells (PASMC) in rats with hypoxic pulmonary vascular structural remodeling,and itsmechanisms.Seventeen Wistar rats were randomly divided into a control group (n=5),a hypoxia group(n=7),and a hypoxia L-Arg group (n=5).The morphologic changes of lung tissues were observed underoptical microscope.Using the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling assay,the apoptosis of PASMC was examined.Fas expression in PASMC wasexamined using immunohistochemistry.The results showed that the percentage of muscularized artery insmall pulmonary vessels,and the relative medial thickness and relative medial area of the small and medianpulmonary muscularized arteries in the hypoxic group were all significantly increased.Pulmonary vascularstructural remodeling developed after hypoxia.Apoptotic smooth muscle cells of the small and median pul-monary arteries in the hypoxia group were significantly less than those in the control group.After 14 d ofhypoxia,Fas expression by smooth muscle cells of median and small pulmonary arteries was significantlyinhibited.L-Arg significantly inhibited hypoxic pulmonary vascular structural remodeling in association withan augmentation of apoptosis of smooth muscle cells as well as Fas expression in PASMC.These resultsshowed that L-Arg could play an important role in attenuating hypoxic pulmonary vascular structural remod-eling by upregulating Fas expression in PASMC,thus promoting the apoptosis of PASMC.     

Fractalkine对大鼠肺动脉平滑肌细胞增殖的影响

目的：观察fractalkine（FKN）对体外培养的大鼠肺动脉平滑肌细胞（PASMCs）增殖的影响。方法：体外培养大鼠PASMCs,加入不同浓度（10-^10、10-^9和10-^8 mol／L）的FKN处理12h、24h和48h,采用四唑盐（MTT）法检测细胞增殖,流式细胞术（FCM）检测细胞周期。结果：MTT试验显示FKN显著促进大鼠PASMCs增殖,此作用呈浓度依赖性。FCM分析显示FKN使S期细胞比例和增殖指数P1值增加。FKN处理PASMCs 12h后,其S期细胞比例和H值即出现增加,24h达高峰。结论：FKN呈浓度依赖方式促进大鼠PASMCs增殖。     

肾上腺髓质素调节诱导型一氧化氮合酶对缺氧肺动脉平滑肌细胞增殖和凋亡的影响

目的:探讨缺氧对肺动脉平滑肌细胞(PASMC)增殖和凋亡的影响以及诱导型一氧化氮合酶(iNOS)的蛋白表达变化及肾上腺髓质素(ADM)在缺氧影响PASMC增殖和凋亡中的作用与意义.方法:离体缺氧培养大鼠PASMC,采用MTT比色法和PCNA的免疫组化法测定细胞增殖反应,采用流式细胞仪法检测细胞凋亡情况,采用Westen blot蛋白印迹法检测iNOS的蛋白表达.结果:①MTT法发现,缺氧24 h组的A值明显高于常氧组(P＜0.01),而缺氧 ADM组明显低于缺氧组(P＜0.01),与常氧组比较差别无显著性(P＞0.05),缺氧 L-NAME组A值明显高于缺氧组和常氧组(P＜0.01).②免疫组化法发现,常氧组PCNA呈弱阳性表达,而缺氧24 h组PCNA呈阳性表达(P＜0.01).ADM明显抑制了缺氧24 h组PCNA的表达(P＜0.01);而L-NAME则促进了缺氧24 h组PCNA的表达(P＜0.01).③流式细胞仪分析发现,常氧组、缺氧组、缺氧 ADM组、缺氧 L-NAME组,在缺氧培养24 h后,其凋亡指数比较差别无显著性(P均＞0.05).④Westen blot发现常氧组大鼠PASMC见少量iNOS表达,缺氧4 h后,表达明显增多(P＜0.01),8h,24 h持续高表达(P＜0.01);L-NAME对iNOS蛋白的表达没有影响.ADM促进iNOS蛋白的表达.结论:①缺氧能促进肺动脉平滑肌细胞低氧性增殖,对肺动脉平滑肌细胞的凋亡无影响.②缺氧能诱导肺动脉平滑肌细胞表达iNOS,ADM能促进iNOS的表达,ADM、iNOS在HPH发展中可能起到抑制作用.     

缺氧时肺动脉内皮细胞与肺动脉平滑肌细胞增殖的相互影响

血管内皮细胞和血管平滑细胞在结构和功能上关系密切,两者的相互在与血管舒缩笔血和壁结构。本文观察了培养的小牛肺动脉内皮细胞（ＰＡＥＣｓ）和肺动平滑肌细胞（ＰＡＳＭＣＳ）缺氧时在细胞增殖方面的相互影响。ＰＡＳＭＣＳ常氧条件培养基（ＣＭ）可使ＰＡＥＣＳ的＾３Ｈ－ＴｄＲ掺入降低约５８％,缺氧ＣＭ对ＰＡＥＣＳ的＾３Ｈ－ＴｄＲ掺入无明显的抑制作用;ＰＡＥＣＳ的常氧ＣＭ使ＰＡＳＭＳ的＾３Ｈ－ＴｄＲ掺入升高约６０     

Comparison of pulmonary vascular response to endogenous nitric oxide inhibition in sheep and pigs living at 2,300 m

To compare the role of nitric oxide in an adaptive process to chronic hypoxia, we examined the effects of endogenous nitric oxide synthase inhibition on pulmonary vascular tone in conscious sheep and pigs living at high altitude. Unanesthetized male sheep (n=6) and pigs (n=5), born and residing in the highlands of Qinghai Province, China (2,300–3,000 m a.s.l.) were studied at that altitude. Pulmonary artery pressure (P_pa), pulmonary artery wedge pressure (P_cwp), and cardiac output (CO) were measured. Pulmonary vascular resistance (PVR) was calculated as (P_pa—P_cwp)/CO. Using a climatic chamber, hemodynamic measurements during exposures to atmospheric pressures corresponding to altitudes of 0, 2,300, and 4,500 m a.s.l. were performed with and without NO inhibition, using N^w-nitro-l-argine (NLA; 20 mg kg^–1), a potent stereospecific competitive inhibitor of nitric oxide synthase. P_pa and PVR at baseline (2,300 m) and during hypoxic exposure (4,500 m) were significantly higher in pigs than in sheep. After NLA administration, P_pa increased and CO decreased in both animals, resulting in significantly increased PVR at baseline and during hypoxic exposure. However, there were no significant differences in the percent increase in basal or hypoxic PVR after NLA administration between sheep and pigs. We conclude that augmented endogenous NO production could contribute to the regulation of pulmonary vascular tone at high altitude in sheep and pigs. However, it is unlikely that NO is responsible for the different pulmonary vascular tones between sheep and pigs at basal condition at moderately high altitude.Communicated by G. Heldmaier     

LRP1 promotes synthetic phenotype of pulmonary artery smooth muscle cells in pulmonary hypertension

Pulmonary hypertension (PH) is characterized by a thickening of the distal pulmonary arteries caused by medial hypertrophy, intimal proliferation and vascular fibrosis. Low density lipoprotein receptor-related protein 1 (LRP1) maintains vascular homeostasis by mediating endocytosis of numerous ligands and by initiating and regulating signaling pathways.Here, we demonstrate the increased levels of LRP1 protein in the lungs of idiopathic pulmonary arterial hypertension (IPAH) patients, hypoxia-exposed mice, and monocrotaline-treated rats. Platelet-derived growth factor (PDGF)-BB upregulated LRP1 expression in pulmonary artery smooth muscle cells (PASMC). This effect was reversed by the PDGF-BB neutralizing antibody or the PDGF receptor antagonist. Depletion of LRP1 decreased proliferation of donor and IPAH PASMC in a β1-integrin-dependent manner. Furthermore, LRP1 silencing attenuated the expression of fibronectin and collagen I and increased the levels of α-smooth muscle actin and myocardin in donor, but not in IPAH, PASMC. In addition, smooth muscle cell (SMC)-specific LRP1 knockout augmented α-SMA expression in pulmonary vessels and reduced SMC proliferation in 3D ex vivo murine lung tissue cultures.In conclusion, our results indicate that LRP1 promotes the dedifferentiation of PASMC from a contractile to a synthetic phenotype thus suggesting its contribution to vascular remodeling in PH.     

低氧对人肺动脉平滑肌和人肺动脉内皮细胞中HMGB1及相关炎症因子表达的影响*

目的:探讨低氧时人肺动脉平滑肌细胞(HPASMC)和人肺动脉内皮细胞(HPAEC)的高迁移率族蛋白1(HMGB1)及相关受体和炎症因子表达,并检测HMGB1对两种细胞增殖、迁移活性的影响。方法:低氧(1%氧浓度,Hypoxia组)及常氧(Control组)条件下培养HPASMC和HPAEC,RealTime-PCR检测两种细胞HMGB1、TLR2、TLR4、TLR9、RAGE、CD24、IL-6 、TNF-a和CXCL8 mRNA等受体和炎性因子的表达。MTS法观察不同浓度HMGB1对HPASMC和HPAEC增殖的影响;划痕法观察HMGB1对HPASMC和HPAEC迁移的影响。结果:Hypoxia组HPASMC、HPAEC中HMGB1及RAGE mRNA表达量较Control 组明显升高(P＜0.05及0.01);Hypoxia组HPAEC中CD24及HPASMC中IL-6 mRNA表达明显增高(P均＜0.05)。MTS结果显示在345 pmol/L 剂量下 HMGB1明显抑制HPAEC的增殖(P＜0.01),而对HPASMC增殖无影响。划痕实验示HMGB1对HPASMC和HPAEC迁移无明显影响。结论:低氧诱导HPAEC、HPASMC 产生HMGB1;HMGB1通过抑制HPAEC增殖引起内皮屏障功能障碍;而低氧进一步刺激HPASMC产生炎症因子。     

NDUFA4L2 in smooth muscle promotes vascular remodeling in hypoxic pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by a progressive increase in pulmonary vascular resistance and obliterative pulmonary vascular remodelling (PVR). The imbalance between the proliferation and apoptosis of pulmonary artery smooth muscle cells (PASMCs) is an important cause of PVR leading to PAH. Mitochondria play a key role in the production of hypoxia-induced pulmonary hypertension (HPH). However, there are still many issues worth studying in depth. In this study, we demonstrated that NADH dehydrogenase (ubiquinone) 1 alpha subcomplex 4 like 2 (NDUFA4L2) was a proliferation factor and increased in vivo and in vitro through various molecular biology experiments. HIF-1α was an upstream target of NDUFA4L2. The plasma levels of 4-hydroxynonene (4-HNE) were increased both in PAH patients and hypoxic PAH model rats. Knockdown of NDUFA4L2 decreased the levels of malondialdehyde (MDA) and 4-HNE in human PASMCs in hypoxia. Elevated MDA and 4-HNE levels might be associated with excessive ROS generation and increased expression of 5-lipoxygenase (5-LO) in hypoxia, but this effect was blocked by siNDUFA4L2. Further research found that p38-5-LO was a downstream signalling pathway of PASMCs proliferation induced by NDUFA4L2. Up-regulated NDUFA4L2 plays a critical role in the development of HPH, which mediates ROS production and proliferation of PASMCs, suggesting NDUFA4L2 as a potential new therapeutic target for PAH.     

慢性间歇性低氧降低急性缺氧对大鼠肺动脉平滑肌细胞膜上电压门控性钾通道的抑制

为了从离子通道水平上探讨机体低氧适应的离子机制,本实验将雄性 SD 大鼠随机分为常氧对照组和慢性间歇性低氧组[氧浓度(10 ± 0.5) %, 间断缺氧每天 8 h]。用酶解法急性分离单个大鼠肺内动脉平滑肌细胞(pulmonary artery smoothmuscle cells, PASMCs),以全细胞膜片钳技术记录 PASMCs 膜上的电压门控性钾通道 (voltage-gated potassium channel, KV) 电流,观察急性缺氧对慢性间歇性低氧大鼠 PASMCs 的 KV 的影响, 为机体适应低氧能力提供实验依据。结果显示:⑴常氧对照组在电流钳下,急性缺氧可使膜电位明显去极化(由-47.2 ±2.6 mV 去极到 -26.7 ±1.2 mV ); 在电压钳下, 急性缺氧可显著抑制 KV电流( 60 mV 时, KV电流密度从 153.4 ± 9.5 pA/pF降到 70.1 ± 10.6 pA/pF), 峰电流的抑制率为(57.6 ± 3.3) %, 电流-电压关系曲线向右下移。⑵慢性间歇性低氧组KV电流密度随低氧时间延长而逐渐减少(慢性低氧10 d后就有显著性意义),电流- 电压关系曲线逐渐右下移。⑶急性缺氧对慢性间歇性低氧大鼠PASMCs KV电流的抑制作用随慢性间歇性低氧时间延长而逐渐减弱。上述观察结果提示慢性间歇性低氧减弱急性缺氧对 KV 的抑制, 这可能是机体低氧适应的一种重要机制。     

A VSV-G pseudotyped HIV vector mediates efficient transduction of human pulmonary artery smooth muscle cells

Attempts were made to infect human vascular smooth muscle cells derived from the pulmonary artery (hPASMC) with two different human immunodeficiency virus (HIV) vector systems. ADA/Luc or HXB2/Luc were generated by cotransfection of luciferase reporter gene vector, pNL4-3-Luc-E- R-, and one of two envelope expressing vectors, pSMADA (R5) or pSMHXB2 (X4). The VSV-G/Luc or VSV-G/GFP were produced by a three-plasmid expression system which consisted of vesicular stomatitis virus G protein (VSV-G) expressing vector, packaging plasmid, and one of two reporter genes (pHR'-CMV-Luc or pHR'-CMV-GFP). We used hPASMC, U87.CD4.CCR5 and U87.CD4.CXCR4 for infection. Neither ADA/Luc nor HXB2/Luc could infect hPASMC, though they could infect U87.CD4 with corresponding coreceptors. On the other hand, the transduction of both VSV-G/Luc and VSV-G/GFP to hPASMC was remarkable. At day 3, the relative proportion of positive cells of hPASMC infected with VSV-G/GFP was 15%. The above finding indicates a direct role of HIV-1 infection in pulmonary hypertension 'a rare complication of HIV-1 infection' and HIV-based vectors could introduce foreign genes into hPASMC for gene therapy of pulmonary hypertension.     

Rab6A GTPase contributes to phenotypic modulation in pulmonary artery smooth muscle cells under hypoxia

Previous studies have demonstrated that hypoxia can induce phenotypic modulation of pulmonary smooth muscle cells; however, the mechanisms remain unclear. The present study aimed to investigate the effect of the GTPase Rab6A-mediated phenotypic modulation and other activities of rat pulmonary artery smooth muscle cells (RPASMCs). We revealed that Rab6A was induced by hypoxia (1% O₂) and was involved in a hypoxia-induced phenotypic switch and endoplasmic reticulum stress (ERS) in RPASMCs. After 48 hours of hypoxia, the expression of the phenotype marker protein smooth muscle actin was downregulated and vimentin (VIM) expression was upregulated. Rab6A was upregulated after 48 hours of hypoxia, and the level of glucose-regulated protein, 78 kDa (GRP78) after 12 hours of hypoxic stimulation was also increased. After transfection with a Rab6A short interfering RNA under hypoxic conditions, the expression levels of GRP78 and VIM in RPASMCs were downregulated. Overall, hypoxia-induced RPASMCs to undergo ERS followed by phenotypic transformation. Rab6A is involved in this hypoxia-induced phenotypic modulation and ERS in RPASMCs.     

Changes in smooth muscle cell pH during hypoxic pulmonary vasoconstriction: a possible role for ion transporters

Hypoxic pulmonary vasoconstriction (HPV) occurs in smooth muscle cells (SMC) from small pulmonary arteries (SPA) and is accompanied by increases in free cytoplasmic calcium ([Ca2+]i) and cytoplasmic pH (pHi). SMC from large pulmonary arteries (LPA) relax during hypoxia, and [Ca2+]i and pHi decrease. Increases in pHi and [Ca2+]i in cat SPA SMC during hypoxia and the augmentation of hypoxic pulmonary vasoconstriction by alkalosis seen in isolated arteries and lungs suggest that cellular mechanisms, which regulate inward and outward movement of Ca2+ and H+, may participate in the generation of HPV. SMC transport systems that regulate pHi include the Na+ - H+ transporter which regulates intracellular Na+ and H+ and aids in recovery from acid loads, and the Na+ -dependent and Na+ -independent Cl-/HCO3- transporters which regulate intracellular chloride. The Na+ -dependent Cl-/HCO3- transporter also aids in recovery from acidosis in the presence of CO2 and HCO3-. The Na+ -independent Cl-/HCO3- transporter aids in recovery from cellular alkalosis. The Na+ - H+ transporter was present in SMC from SPA and LPA of the cat, but it seemed to have little if any role in regulating pHi in the presence of CO2 and HCO3-. Inhibiting the Cl-/HCO3- transporters reversed the normal direction of pHi change during hypoxia, suggesting a role for these transporters in the hypoxic response. Future studies to determine the interaction between pHi, [Ca2+]i and HPV should ascertain whether pHi and [Ca2+]i changes are linked and how they may interact to promote or inhibit SMC contraction.