K-ATP channel openers facilitate glutamate uptake by GluTs in rat primary cultured Astrocytes

Increasing evidence, including from our laboratory, has revealed that opening of ATP sensitive potassium channels(K-ATP channels) plays the neuronal protective roles both in vivo and in vitro. Thus K-ATP channel openers (KCOs) have been pro-posed as potential neuroprotectants. Our previous studies demonstrated that K-ATP channels could regulate glutamate uptake activity in PC12 cells as well as in synaptosomes of rats. Since glutamate transporters(GluTs) of astrocytes play crucial roles in glutamate up-take and KATP channels are also expressed in astrocytes, the present study showed whether and how KATP channels regulated the function of GluTs in primary cultured astrocytes. The results showed that nonselective KCO pinacidil, selective mitochondrial KCO diazoxide, novel, and blood-brain barrier permeable KCO iptakalim could enhance glutamate uptake, except for the sarcolemmal KCO P1075. Moreover pinacidil, diazoxide, and iptakalim reversed the inhibition of glutamate uptake induced by 1-methyl-4-phenylpyridinium (MPP+). These potentiated effects were completely abolished by mitochondrial K-ATP blocker 5-hydroxydecanoate. Furthermore, either diazoxide or iptakalim could inhibit MPP+-induced elevation of reactive oxygen species(ROS) and phosphoryla-tion of protein kinases C(PKC). These findings are the first to demonstrate that activation of K-ATP channel, especially mitochondri-al K-ATP channel, improves the function of GluTs in astrocytes due to reducing ROS production and downregulating PKC phospho-rylation. Therefore, the present study not only reveals a novel pharmacological profile of KCOs as regulators of GluTs, but also pro-vides a new strategy for neuroprotection.     

线粒体KATP在吡那地尔预处理后失血性休克大鼠组织血流灌注和线粒体功能保护效应中的作用

目的 观察吡那地尔(pinacidil)预处理对失血性休克大鼠血流灌注和线粒体功能的保护效应,及其与线粒体ATP激活钾通道[adenosine triphosphate(ATP)-activated potassium channels,KATP]的关系.方法 Wiser大鼠60只,随机数字表法分为:正常对照组、休克组...     

Protective effects of pinacidil hyperpolarizing cardioplegia on myocardial ischemia reperfusion injury by mitochondrial KATP channels

Background  Many studies have indicated that hyperpolarizing cardioplegia is responsible for myocardial preservation and researchers have suggested that the adenosine triphosphate-sensitive potassium channels (K_ATP) were the end effectors of cardio-protection. But whether mitochondrial K_ATP plays an important role in hyperpolarizing cardioplegia is not apparent. The present study investigated the effect of hyperpolarizing cardioplegia containing pinacidil (a nonselective K_ATP opener) on ischemia/reperfusion injury in rat hearts, especially the role of mitochondrial K_ATP in pinacidil hyperpolarizing cardioplegia.

Methods  Sprague-Dawley rat hearts were Langendorff-perfused for 20 minutes with Krebs-Henseleit buffer at 37°C before equilibration. Cardiac arrest was then induced in different treatments: there was no arrest and ischemia in the normal group, the control group were arrested by clamping the aorta, depolarizing caidioplegia (St. Thomas solution containing 16 mmol/L KCl) and hyperpolarizing cardioplegia groups used St. Thomas solution containing 0.05 mmol/L pinacidil and 5 mmol/L KCl to induce cardiac arrest in group hyperkalemic and group pinacidil, in group hyperkalemic + 5-hydroxydecanote (5HD) and Pinacidil + 5HD, 5HD (0.1 mmol/L) was added to the above two solutions to block mitochondria K_ATP channels. Global ischemia was then administrated for 40 minutes at 37°C, followed by 30 minutes of reperfusion. At the end of equilibration and reperfusion, hemodynamics, ultrastructure, and mitochondrial function were measured.

Results  In the control group, ischemia/reperfusion decreased the left ventricular developed pressure, heart rate, coronary flow, mitochondrial membrane potential, impaired mitochondrial respiratory function, increased reactive oxygen species and left ventricular end diastolic pressure. Damage to myocardial ultrastructure was also evident. Both depolarized arrest and especially hyperpolarized cardioplegia significantly reduced these lesions. 5HD partially blocked the beneficial effects of pinacidil cardioplegia but showing no effects on hyperkalemic arrest.

Conclusions  Pinacidil cardioplegia provides better cardioprotection with preservation of hemodynamics, ultrastructure, and mitochondrial function than traditional cardioplegia. The mitochondria K_ATP channels may play an important role in the protection mechanism.

     

Cardioprotective effects of mitochondrial KATP channels activated at different time

Backgroud Recent studies in adult hearts have indicated that KATP channels in the inner mitochondrial membrance are responsible for the protection. And we investigated whether opening of mitochondrial KATP channels (mKATP) could provide myocardial protection for immature rabbits and determined its role in cardioprotection.Methods Thirty-four 3-4-week-old rabbits, weighing 300-350 g, were divided randomly into five groups: Group Ⅰ (control group, n=8); Group Ⅱ ［diazoxide preconditioning group; n=8; the hearts were pretreated with 100 μmol/L diazoxide for 5 minutes followed by 10-minute wash out with Krebs-Henseleit buffer (KHB)］; Group Ⅲ ［diazoxide+5-hydroxydeconate (5-HD) preconditioning group; n=5; the hearts were pretreated with 100 μmol/L diazoxide and 100 μmol/L 5-HD); Group Ⅳ (diazoxide+cardioplegia group; n=8; cardioplegia containing 100 μmol/L diazoxide perfused the hearts for 5 minutes before ischemia); Group Ⅴ (diazoxide+5-HD+cardioplegia group; n=5; the cardioplegia contained 100 μmol/L diazoxide and 100 μmol/L 5-HD). All hearts were excised and connected to langendrff perfusion system and passively perfused with KHB at 38℃ under a pressure of 70 cmH2O. After reperfusion, the recovery rate of left ventricular diastolic pressure (LVDP), ±dp/dtmax, coronary flow (CF), the creatinine kinase (CK), lactate dehydrogenase (LDH), aspartate aminotransferase (AST) in coronary sinus venous effluent and the tissue ATP were measured. Mitochondria were evaluated semiquantitatively by morphology.Results After ischemia and reperfusion (I/R), the two groups that were treated by diazoxide only (Groups Ⅱ and Ⅳ) had a significant improvement in LVDP, ±dp/dtmax, and CF recovery. AST, LDH, and CK were decreased, and the levels of tissue ATP in the two groups were higher. Mitochondria was protected better in Group Ⅳ than in other groups. Conclusions Activating mKATP channels before and during ischemia can similarly protect immature rabbit hearts, and the mechanism is related to the direct protective effect on mitochondria. Opening of mKATP channel during ischemia provides a better protection for mitochondria than it does before ischemia.     

线粒体ATP敏感的钾通道和缺血再灌注损伤

细胞上存在两种ATP敏感的钾通道,一是位于细胞膜上的ATP敏感的钾通道;二是位于线粒体膜上的ATP敏感的钾通道。最近的药理学和分子生物学研究认为线粒体ATP敏感的钾通道开放对器官缺血再灌注损伤有保护作用。这些研究表明线粒体ATP敏感的钾通道在器官保护中具有关键作用。本文介绍了线粒体ATP敏感钾通道的结构和生理学特性,线粒体在缺血再灌注损伤中的生理变化及可能的机制,还有在器官保护中的研究进展。     

ATP敏感性钾通道开放剂的脑保护作用研究

细胞上存在两种三磷酸腺苷敏感性钾(KATP)通道,一是位于细胞膜上的ATP敏感的钾通道;二是位于线粒体膜上的ATP敏感的钾通道。KATP通道广泛存在于各种脑区,若给予KATP开放剂则可以使其开放发挥对脑的保护作用。越来越多的研究表明,KATP通道在脑缺氧缺血等病理状态下被激活开放,使大量K+外流,细胞膜超极化,从而使Na+、Ca2+内流减少,避免或减轻钙超载、减少能耗、减轻兴奋性氨基酸及氧自由基释放,保护脑细胞。     

Kir6.2构成的ATP敏感性钾通道在苯环己哌啶诱导的精神分裂症阴性症状中的作用（英文）

目的：ATP敏感性钾（K-ATP）通道对多巴胺和谷氨酸能传导具有重要的调节作用,而多巴胺和谷氨酸能传导之间相互作用是精神分裂症病理机制的重要神经化学基础。因此,我们应用Kir6.2（主要表达在神经元的K-ATP亚基）敲除小鼠,通过苯环己哌啶诱导强迫游泳不动时间的延长,模拟精神分裂症的阴性症状,从而研究K-ATP通道在其中的作用。方法：连续注射14d苯环己哌啶（10 mg.kg-1,i.p.）后,通过观察强迫游泳实验中小鼠不动时间的长短,评价Kir6.2敲除对精神分裂症阴性症状中抑郁样表现的影响;应用高效液相色谱联合电化学检测法观察纹状体多巴胺及其代谢产物、多巴胺更新率的改变;应用溴脱氧尿嘧啶核苷插入法观察海马齿状回颗粒下区神经干细胞增殖的改变;应用Western blot技术观察磷酸化Akt水平的变化。结果：Kir6.2敲除取消了苯环己哌啶引起的强迫游泳不动时间的延长。不仅如此,Kir6.2敲除还抑制了苯环己哌啶诱导的纹状体多巴胺更新率的增加、海马齿状回颗粒下区神经干细胞增殖的减弱,以及磷酸化Akt水平升高。结论：Kir6.2组成的K-ATP通道参与了苯环己哌啶诱导的精神分裂症阴性症状,阻断K-ATP通道有望成为治疗精神分裂症的新策略。     

新型katp开放剂埃他卡林对原代培养人肺动脉平滑肌细胞pcna mrna表达的影响

目的:观察新型ATP敏感性钾通道(KATP)开放剂埃他卡林(IPT)对原代培养人肺动脉平滑肌细胞增殖细胞核抗原(PCNA)mRNA表达的影响。方法:分离3～4级人肺小动脉,按照组织贴块法原代培养人肺动脉平滑肌细胞,分成对照组、缺氧组、缺氧+埃他卡林或吡那地尔组及缺氧+埃他卡林或吡那地尔+格列本脲组,应用实时荧光定量逆转录聚合酶链反应(FQ-RT-PCR)技术检测细胞PCNA mRNA表达。结果:缺氧使人肺动脉平滑肌细胞PCNA mRNA表达增加(3.90±0.24)倍,与对照组比较差异有显著性(P<0.01);相同条件下,在缺氧的同时,分别在培养液中加入IPT 10-7、10-6、10-5 mol/L,PCNA mRNA表达分别下降(26.00±2.01)%、(55.33±4.04)%、(79.00±1.00)%,与缺氧组比较差异均有显著性(P均<0.01);加入IPT 10-5mol/L前30 min,预先加入格列本脲(GLI)10-5 mol/L,IPT的抑制作用抵消,与缺氧+IPT 10-5 mol/L组比较差异有显著性(P<0.01)。结论:IPT通过激活细胞KATP通道,浓度依赖性地抑制缺氧时原代培...     

缝隙连接蛋白43在缺血性心律失常中的作用

目的探讨心肌缺血时,心肌缝隙连接蛋白43(connexin43,Cx43)与缺血性心律失常的关系。方法对戊巴比妥钠麻醉大鼠进行30min的冠状动脉缺血。大鼠分为不处理或者接受缺血预适应(ischemic preconditioning,IPC)、静脉注射线粒体ATP磷酸敏感性钾通道(mitoKATP)开放剂二氮嗪(Dia)3组,其余2组为在接受IPC、Dia的基础上加用5羟基奎酸(5-HD)。测量各组的血流动力学指标和心律失常。采用Western blotting检测Cx43的磷酸化程度。结果与对照组相比,IPC、Dia能促进Cx43磷酸化,减少心律失常的发生率,线粒体ATP敏感性钾通道阻断剂5-HD能消除IPC和Dia的上述作用。结论IPC通过开放线粒体ATP敏感性钾通道促进Cx43磷酸化和电耦联,进而抑制心律失常的发生。     

ATP 敏感钾通道在神经退行性疾病中的研究进展

ATP 敏感钾通道（ATP-sensitive potassium channel,KATP）,因其通道活性受ATP/ADP 的影响而得名。KATP 是一种耦联细胞电活动和细胞代谢的特殊通道,通道功能在正常状态下,对于维持神经细胞线粒体膜电位、抑制细胞凋亡有重要作用。KATP 广泛存在于胰岛细胞、心肌、骨骼肌、血管平滑肌和神经细胞等组织中。近几年的研究发现KATP 参与了多种疾病的发病过程,该文对ATP 敏感钾通道在神经退行性疾病中的研究进展作了综述。     

开放血管平滑肌细胞Kir6.1/SUR2B降低去窦弓神经大鼠血压波动性

目的 探讨心血管系统不同分子组成的ATP敏感钾通道(KATP)在降低去窦弓神经(SAD)大鼠血压波动性(BPV)中的作用.方法 建立SAD大鼠模型,利用计算机化清醒自由活动大鼠血流动力学监测技术,观察非选择性KATP开放剂吡那地尔、Kir6.1/Sur2B和Kir6.1/Sur1选择性开放剂二氮嗪对SAD大鼠BPV的影响;并观察用Kir6.1/Sur1选择性阻断剂5-羟基癸酸盐(5-HD)、Kir6.2/Sur2A选择性阻断剂HMR1098阻断KATP后,吡那地尔和二氮嗪对SAD大鼠BPV作用的改变.结果 吡那地尔和二氮嗪能够降低SAD大鼠BPV(P＜0.01),阻断Kir6.1/Sur1、Kir6.2/Sur2A后不改变吡那地尔和二氮嗪对BPV的降低作用.结论 开放血管平滑肌细胞Kir6.1/Sur2B能够降低SAD大鼠的BPV.     

冠心康对大鼠缺血心肌细胞ATP敏感钾通道亚基Kir6.1、Kir6.2、SUR2A和SUR2B表达的影响

目的：通过观察中药复方冠心康对大鼠缺血心肌细胞ATP敏感钾（ATP-sensitive potassium,K_（ATP））通道亚基的影响,探讨冠心康保护心血管、抗心肌缺血的可能作用机制。方法：48只SPF级Wistar大鼠随机分为正常组、模型组、格列本脲组、吡那地尔组、冠心康组、冠心康加格列本脲组。采用酶解法分离大鼠心室肌细胞,用无钙台式液灌流10 min、停灌30 min、再灌注45 min模拟心肌缺血再灌注损伤。将药物直接加入细胞液中（格列本脲10μmol/L、吡那地尔50μmol/L、冠心康注射液1 ml/L）充分作用后,4℃放置24 h。采用实时荧光定量多聚酶链式反应法及蛋白质印迹法检测各组心肌细胞K_（ATP）亚基Kir6.1、Kir6.2、SUR2A和SUR2B的mRNA表达及蛋白含量。结果：正常大鼠心肌细胞可见SUR2A、Kir6.1和Kir6.2蛋白及mRNA的表达,而SUR2B蛋白几乎不表达。模型组K_（ATP）各个亚基蛋白及mRNA的表达均较正常组有一定程度的增加。与模型组比较,吡那地尔可显著增加K_（ATP）各亚基mRNA及蛋白的表达,格列本脲可阻断这一作用;冠心康可明显增加K_（ATP）通道各亚基mRNA及蛋白的表达。结论：复方冠心康具有明显的促进K_（ATP）开放的作用,从而起到心血管保护作用。     

马桑内酯对锥体神经元ATP敏感钾通道的作用

目的　研究致痫剂马桑内酯 (CL)对大鼠海马锥体神经细胞膜 ATP敏感钾通道 (KATP)的影响及KATP在癫痫发病中的作用。方法　用膜片钳单通道电流记录和组织培养技术对锥体神经元 ATP敏感钾通道进行研究。结果　对称性高钾溶液条件下 ,KATP的翻转电位接近 0 m V,通道可被 TEA阻断 ;0 .5 mol/ L的 ATP可抑制通道活动 ;30μmol/ L的二磷酸核苷 (DNP)可使通道开放增多 ;其电流 -电压曲线可被直线拟合 ,通道电导值为78.2 3± 12 .0 4 p S。 CL可明显激活 KATP,优降糖能抑制激活的通道。结论　在 CL诱导的癫痫发作中 ,ATP敏感钾通道开放的作用是降低动作电位频率、保护神经元 ,可能起一种负反馈调节作用     

钾通道开放剂拮抗内皮素-1的缩血管作用

利用离体猪心冠状动脉环，研究了KATP开放剂吡那地尔（PIN）和克卡里木（CRO）对内皮素－1（ET－1）缩血管作用的影响。结果表明，PIN和CRO均使ET－1的量－效曲线右移，并降低最大反应。当ET－1（30nmol／L）达最大效应后，累加剂量的PIN和CRO产生剂量依赖性的抑制作用。结果提示，KATP开放剂对ET－1收缩冠状动脉的拮抗作用，可能是其抗心肌缺血的机制之一。     

过敏性哮喘豚鼠气道平滑肌三磷酸腺苷敏感钾通道动力学特性

目的探讨过敏性哮喘豚鼠气道平滑肌三磷酸腺苷敏感钾通道(KATP通道)的单通道动力学特性变化。方法将12只4月龄豚鼠随机分为对照组和过敏性哮喘组,每组6只。急性分离出豚鼠3～4级支气管的平滑肌细胞,应用膜片钳内面向外式记录气道平滑肌KATP通道单通道电流,并分析其动力学特性。结果当钳制电压在-60 mV时,过敏性哮喘组通道平均开放时间明显短于对照组(P<0.05);当钳制电压在-40 mV和-60 mV时,过敏性哮喘组通道平均关闭时间明显长于对照组(P<0.05)。当钳制电压在-40 mV和-60 mV时,过敏性哮喘组通道开放概率明显低于对照组(P<0.01)。结论过敏性哮喘时KATP通道单通道动力学特性发生改变,使气道平滑肌对抗去极化能力减弱,可能是气道高反应性中平滑肌收缩反应增强的重要原因之一。     

吗啡、纳络酮对培养星形胶质细胞谷氨酸摄取功能的影响

目的：探讨不同浓度吗啡及纳洛酮对培养星形胶质细胞摄取谷氨酸功能的影响。方法：分离培养海马星形胶质细胞。传代提纯达98％以上（免疫组化检测GFAP进行鉴定）,通过掺入H^3-谷氨酸进行培养,观察吗啡,纳络酮及吗啡加纳络酮对星形胶质细胞摄取谷氨酸的影响。结果：单独应用吗啡,纳络酮均可增强星形胶质细胞摄取谷氨酸的功能（P＜0．01）,联合应用则对吗啡或纳络酮的谷氨酸提取有抑制作用。结论：吗啡,纳络酮可调节星形质细胞的谷氨酸的提取。     

Effect of mitochondrial KATP channel on voltage-gated K+ channel in 24 hour-hypoxic human pulmonary artery smooth muscle cells

Background Hypoxic pulmonary hypertension (HPH) is initiated by inhibition of O2-sensitive, voltage-gated (Kv) channels in pulmonary arterial smooth muscle cells (PASMCs). The mechanism of hypoxic pulmonary hypertension has not yet been fully elucidated. The mitochondrial ATP-sensitive K+ channel (MitoKATP) is extremely sensitive to hypoxia, and is a decisive factor in the control of mitochondrial membrane potential (ΔΨm). This study investigated the changes of cell membrane potential and Kv channel in cultured human pulmonary artery smooth muscle cell (hPASMC) exposed to 24 hour-hypoxia, and explored the role of MitoKATP and ΔΨm in this condition. Methods Fresh human lung tissues were obtained from the patients undergoing a chest operation. hPASMCs were isolated, cultured, and divided into 6 groups: ① control group, cultured under normoxia; ② diazoxide group, cultured in normoxia with diazoxide, an opener of MitoKATP; ③ 5-HD group, cultured in normoxia with sodium 5-hydroxydecanoate (5-HD), an antagonist of MitoKATP; ④ 24 hour-hypoxia group; ⑤ 24 hour-hypoxia + diazoxide group; and ⑥ 24 hour-hypoxia + 5HD group. Whole-cell patch-clamp technique was used to trace the cell membrane K+ currents. The expressions of cell membrane Kv1.5 mRNA and protein were determined by RT-PCR and Western blot technique, respectively. The relative changes in mitochondrial potential were tested with rhodamine fluorescence (R-123) technique. Results After exposure to diazoxide for 24 hours, the intensity of R-123 fluorescence in normoxic hPASMCs was significantly increased compared with control group (P&lt;0.05), but there were no significant changes in these tests after the hPASMCs had been exposed to 5-HD for 24 hours. Twenty-four hour-hypoxia or 24 hour-hypoxia + diazoxide could markedly increase the intensity of R-123 fluorescence in hPASMC and the changes were more significant in 24 hour-hypoxia +diazoxide group than in 24 hour-hypoxia group (P&lt;0.05) although 5-HD could partly weaken the effect of 24 hour-hypoxia on the intensity of R-123 fluorescence. After exposure to diazoxide for 24 hours, the cell membrane K+ currents and the expression of cell membrane Kv1.5 mRNA and protein in normoxic hPASMCs were significantly decreased compared with control group (P&lt;0.05), but there were no significant changes in these tests after the hPASMCs had been exposed to 5-HD for 24 hours. Also, 24 hour-hypoxia or 24 hour-hypoxia + diazoxide decreased the cell membrane K+ currents and the expression of Kv1.5 mRNA and protein (P&lt;0.05) but the changes were more significant in 24 hour-hypoxia + diazoxide group than in 24 hour-hypoxia group (P&lt;0.05). Again, 5-HD could partly weaken the inhibitory effect of 24 hour-hypoxia on the cell membrane K+ currents and the expression of Kv1.5 mRNA or protein (P&lt;0.05). Conclusions The opening of MitoKATP followed by a depolarization of ΔΨm in hypoxia might contribute to the alterations in the expression of cell membrane Kv1.5 mRNA and protein leading to change in the cell membrane potential of hypoxic hPASMCs. This might be a mechanism of the development of hypoxic pulmonary hypertension.     

丹参对大鼠大脑缺血时神经细胞ATP敏感性钾通道的影响

目的探讨丹参对大脑缺血时神经细胞ATP敏感性钾通道的影响.方法利用膜片钳内面向内外式记录方法,观察了不同浓度(1、5、10 m/ml)丹参时对ATP敏感性钾通道的活性和敏感性的影响.结果丹参降低单个通道内向电流开放概率,激活通道的多级开放,降低通道对胞内ATP的敏感性.结论丹参有类似钾通道开放剂作用,具有保护脑缺血缺氧损伤作用.     

埃他卡林对脂多糖、油酸、二甘醇等所致肾脏损伤的影响

目的 观察埃他卡林对脂多糖、油酸和二甘醇等不同因素所致肾脏损伤的影响。方法 采用大鼠股静脉注射2%醋酸铅致敏后注射脂多糖1 μg (1 ml/kg),4 h造成内毒素休克肾损伤模型,大鼠左肾动脉注射油酸0.15 ml/kg,24 h造成油酸所致肾损伤模型,分别在造模前3 d及1 h,以埃他卡林1,3,9 mg/（kg·d）灌胃给药;小鼠腹腔注射二甘醇10 g/kg后,立即以埃他卡林1,3,9 mg/（kg·d）灌胃给药6 d,第7天造模成功。3种模型建立后,观察血清肌酐、尿素氮水平和肾脏形态学变化,评价肾脏功能。结果 （1）内毒素性休克大鼠血清肌酐和尿素氮水平显著升高,组织病理显示有肾小球微血栓、肾小管上皮肿胀和管腔内蛋白管型形成。埃他卡林9 mg/kg组能明显降低血清尿素氮和肌酐水平,改善上述病理变化。（2）左肾动脉注射油酸大鼠血清肌酐和尿素氮水平显著升高,组织病理显示肾小球内皮细胞坏死,球囊腔减小,肾小管间质充血且管腔内有蛋白管型形成。埃他卡林对油酸所致大鼠肾脏损伤无显著性改善作用。（3）二甘醇肾损伤小鼠血清肌酐水平显著性升高,埃他卡林9 mg/kg组血清肌酐水平恢复至正常。结论 埃他卡林不适合于脂多糖、油酸所致肾脏损伤的防治,埃他卡林可否用于二甘醇所致肾损伤的治疗值得进一步研究。     

Effects of mitochondrial ATP-sensitive K+ channel on protein kinase C pathway and airway smooth muscle cell proliferation in asthma

The effects of ATP-sensitive mitochondrial K + channel(mitoK ATP) on mitochondrial membrane potential(Δψm),cell proliferation and protein kinase C alpha(PKCα) expression in airway smooth muscle cells(ASMCs) were investigated.Thirty-six Sprague-Dawley(SD) rats were immunized with saline(controls) or ovalbumin(OVA) with alum(asthma models).ASMCs were cultured from the lung of control and asthma rats.ASMCs were treated with diazoxide(the potent activator of mitoK ATP) or 5-hydroxydencanote(5-HD,the inhibitor of mitoK ATP).Rhodamine-123(R-123) was used to detect Δψm.The expression of PKCα protein was examined by using Western blotting,while PKCα mRNA expression was detected by using real-time PCR.The proliferation of ASMCs was measured by MTT assay and cell cycle analysis.In diazoxide-treated normal ASMCs,the R-123 fluorescence intensity,protein and mRNA levels of PKCα,MTT A values and percentage of cells in S phase were markedly increased as compared with untreated controls.The ratio of G 0 /G 1 cells was decreased(P<0.05) in diazoxide-treated ASMCs from normal rats.However,there were no significant differences between the ASMCs from healthy rats treated with 5-HD and the normal control group.In untreated and diazoxide-treated ASMCs of asthmatic rats,the R-123 fluorescence intensity,protein and mRNA levels of PKCα,MTT A values and the percentage of cells in S phase were increased in comparison to the normal control group.Furthermore,in comparison to ASMCs from asthmatic rats,these values were considerably increased in asthmatic group treated with diazoxide(P<0.05).After exposure to 5-HD for 24 h,these values were decreased as compared with asthma control group(P<0.05).In ASMCs of asthma,the signal transduction pathway of PKCα may be involved in cell proliferation,which is induced by the opening of mitoK ATP and the depolarization of Δψm.