核因子κB在蛋白激酶C诱导哮喘模型大鼠气道平滑肌细胞增殖中的作用

目的:探讨核因子κB(NF-κB)在蛋白激酶C(PKC)致哮喘模型大鼠气道平滑肌细胞(ASMCs)增殖中的作用。方法:16只Wistar大鼠随机分为哮喘组(8只)和对照组(8只)。应用PKC激动剂PMA和NF-κB抑制剂PDTC干预哮喘组和对照组大鼠ASMCs。采用流式细胞术、MTT法及增殖细胞核抗原(PCNA)免疫荧光技术等方法检测ASMCs增殖;免疫荧光技术及电泳迁移率改变分析(EMSA)检测NF-κB活性。结果:PMA干预哮喘组ASMCs后S期细胞比例、A值、PCNA表达率、NF-κBp65阳性率及结合带的灰度值均显著高于未干预的哮喘组ASMCs(均P<0.05),PDTC预处理后再给予PMA上述指标均低于仅用PMA干预及未干预者(均P<0.05)。仅用PDTC处理的哮喘组ASMCs上述指标均低于未干预的ASMCs(均P<0.05)。结论:NF-κB参与哮喘大鼠ASMCs增殖,在其增殖中存在着PKC-NF-κB信号途径。     

核因子κB在蛋白激酶C诱导哮喘模型大鼠气道平滑肌细胞增殖中的作用

目的： 探讨核因子κB（NF-κB）在蛋白激酶C（PKC）致哮喘模型大鼠气道平滑肌细胞（ASMCs）增殖中的作用。方法： 16只Wistar大鼠随机分为哮喘组（8只）和对照组（8只）。应用PKC激动剂PMA和NF-κB抑制剂PDTC干预哮喘组和对照组大鼠ASMCs。采用流式细胞术、MTT法及增殖细胞核抗原（PCNA）免疫荧光技术等方法检测ASMCs增殖；免疫荧光技术及电泳迁移率改变分析(EMSA)检测NF-κB活性。 结果： PMA干预哮喘组ASMCs 后S期细胞比例、A值、PCNA表达率、NF-κBp65阳性率及结合带的灰度值均显著高于未干预的哮喘组ASMCs (均P<0.05)，PDTC预处理后再给予PMA上述指标均低于仅用PMA干预及未干预者(均P<0.05)。仅用PDTC处理的哮喘组ASMCs上述指标均低于未干预的ASMCs (均P<0.05)。结论： NF-κB参与哮喘大鼠ASMCs增殖，在其增殖中存在着PKC－NF-κB信号途径。     

PKC信号通道对严重创伤性休克大鼠血管舒缩功能的调节作用

目的探讨蛋白激酶C(PKC)信号通道是否参与了严重创伤性休克后血管舒缩功能的调控。方法取严重创伤性失血性休克大鼠的腹腔动脉(CA),观察PKC激活剂PMA及PKC抑制剂Staurosporine对休克后去甲肾上腺素(NE)、氯化钾(KC l)诱导的血管收缩反应的影响,以及PMA对乙酰胆碱(ACh)介导的内皮依赖性舒张(EDR)和硝普钠(SNP)介导的内皮非依赖性舒张(EIDR)反应的影响。结果严重创伤性失血性休克大鼠腹腔动脉对NE、KC l诱导的收缩反应以及ACh、SNP介导的舒张反应都显著降低;PMA(0.01、0.1、1μmol/L)对NE、KC l诱导的休克血管收缩反应有显著的增强作用,且呈浓度依赖性;Staurosporine(100 nmol/L)可使休克血管对NE、KC l的反应性进一步降低,同时Staurosporine预处理能显著抑制PMA增强休克血管收缩反应的作用;PMA(0.1μmol/L)可使ACh和SNP诱导的舒张反应都进一步降低。结论PKC信号通道对严重创伤后的血管舒缩功能具有重要的调节作用。     

周期蛋白D1在蛋白激酶C调控哮喘大鼠气道平滑肌细胞增殖中的作用

目的：观察蛋白激酶C(PKC)激活后哮喘大鼠气道平滑肌细胞(ASMCs)周期蛋白D1(cyclin D1)的表达变化及两者表达相关性，探讨cyclin D1在PKC调控哮喘大鼠ASMCs增殖中所起的作用。方法:卵清蛋白（OVA）吸入制备SD大鼠2周哮喘模型，原代培养ASMCs。采用正常大鼠（N组）和模型大鼠（A组）第3-6代细胞，分别应用PKC特异性激活剂12-肉豆蔻酰-13-乙酸佛波酯（PMA）及抑制剂Ro-31-8220干预ASMCs, 根据不同处理分为4组：（1）空白组；（2）10 nmol/L PMA组；(3)10 nmol/L PMA+5 μmol/L Ro-31-8220组； (4)5 μmol/L Ro-31-8220组。采用流式细胞术，四甲基偶氮唑盐（MTT）法，增殖细胞核抗原（PCNA）染色等方法观察药物对ASMCs增殖的影响。RT-PCR方法检测PKC-α和cyclin D1 mRNA表达水平，Western blotting方法检测PKC-α和cyclin D1蛋白表达水平。线性相关分析评价PKC-α和cyclin D1表达水平的关系。结果:（1）在哮喘组，与空白对照比较，PMA组、Ro-31-8220组S+G2/M期比例、吸光度A值、PCNA阳性表达率，差异显著（P<0.01）。在正常组，与空白对照相比，PMA组、Ro-31-8220组S+G2/M期比例、吸光度A值、PCNA阳性表达率差异均显著（P<0.01）。（2）哮喘组内PMA组、Ro-31-8220组PKC-α以及cyclin D1 mRNA 和蛋白表达水平与空白对照比较，差异显著（P<0.01）。正常组和哮喘组变化趋势一致。(3)在mRNA水平，大鼠ASMCs PKC-α和cyclin D1的表达呈明显正相关(r=0.476，P<0.05)，在蛋白水平两者的表达亦呈明显正相关(r=0.899, P<0.01)。结论:PKC-α能促进正常大鼠和哮喘大鼠ASMCs增殖，其在基因和蛋白的表达水平与cyclin D1的表达呈正相关，提示PKC-α可能通过调节cyclin D1而影响ASMCs的增殖。     

胡椒碱抑制AngⅡ诱导大鼠气道平滑肌细胞增殖和迁移

目的探究胡椒碱对血管紧张素Ⅱ(AngⅡ)对大鼠气道平滑肌细胞(ASMCs)增殖和迁移的影响。方法用改良组织块和胰蛋白酶消化联合培养原代细胞ASMCs。MTT检测AngⅡ及其受体拮抗剂losartan对细胞增殖活性的影响。AngⅡ和不同浓度胡椒碱作用ASMCs后,MTT、流式细胞术和Transwell分别检测细胞增殖、细胞周期以及细胞迁移;ERK1/2抑制剂PD98059和losartan干预后,Western blot检测cyclin D1、MMP-9、p-ERK1/2、ERK1/2和β-actin等蛋白表达。结果 AngⅡ(10~(-8)、10~(-7)、10~(-6)和10~(-5)mol/L)作用24 h后,可浓度依赖性地促进ASMCs增殖(P0.05),其中10~(-7)mol/L AngⅡ促进效果最为显著;losartan处理则抑制AngⅡ诱导的ASMCs增殖(P0.05)。10~(-7)mol/L AngⅡ处理组ASMCs增殖活性、S期细胞分布比例、细胞迁移数目和蛋白质(cyclin D1、MMP-9和p-ERK1/2)表达均明显增加(P0.05);而胡椒碱(10、25、50和100μmol/L)处理可浓度依赖性地减轻AngⅡ诱导的上述效应。并且,PD98059和losartan亦能阻断AngⅡ对ASMCs p-ERK1/2、cyclin D1和MMP-9的上调作用。结论胡椒碱能通过ERK1/2通路抑制AngⅡ诱导的大鼠ASMCs增殖和迁移。     

高糖上调大鼠主动脉平滑肌细胞骨桥蛋白表达

目的 探讨高糖对大鼠血管平滑肌细胞（VSMCs）骨桥蛋白（OPN）表达的影响及机制。方法 SD大鼠腹腔注射链脲佐菌素复制Ⅰ型糖尿病模型,免疫组化、RT-PCR和western blot检测大鼠主动脉OPN和PCNA的表达;大鼠主动脉VSMCs经含正常糖(5.5mmol/L)、高糖(25mmol/L)、甘露醇(25mmol/L)、高糖+GF109203X（蛋白激酶C抑制剂,10μmol/L),高糖+ NAC（N-acetyl-l-cysteine,NF-κB抑制剂,10μmol/L)的DMEM处理48 h,免疫荧光及western blot检测OPN的表达,western blot 分析PCNA、PKC和 p65的表达。结果 高糖血症大鼠主动脉VSMCs高表达OPN及PCNA。原代VSMCs经高糖刺激后OPN、PCNA、PKC及p65表达明显增加;GF109203X和NAC均可下调PCNA的高表达,但仅GF109203X抑制高糖诱导的OPN高表达。结论 高糖可能通过激活PKC信号诱导OPN表达并促进VSMCs增殖从而在糖尿病性血管并发症中起作用。     

蛋白激酶C的活性变化对人肝癌细胞增殖及端粒酶表达的影响

目的:揭示蛋白激酶C(PKC)活性变化对人肝癌细胞增殖及端粒酶表达的影响。方法: 体外以PKC激活剂PMA(phorbol-12-myristate-13-acetate)及其抑制剂星形孢菌素(staurosporine,SP)作用于人肝癌细胞系(BEL-7402)48 h后,运用TRAP-银染(telomeric repeat amplification protocol silver staining)与计算机图像凝胶扫描记录技术结合的方法来揭示细胞端粒酶活性、PKC变化与细胞增殖的关系。结果:PMA与SP的作用,促进其细胞增殖抑制的同时,抑制其细胞端粒酶活性表达。结论:PKC的活性变化与人肝癌细胞增殖相关,并可能与端粒酶的活性表达关联。     

核因子-κB抑制剂在蛋白激酶C对低氧性肺动脉高压大鼠肺动脉环反应性影响中的作用

目的:探讨核因子-κB抑制剂在蛋白激酶C对低氧性肺动脉高压大鼠离体肺动脉环反应性影响中的作用。方法:复制低氧性肺动脉高压大鼠模型,测定肺动脉平均压(mPAP)、右心室重/(左心室+室间隔)重。取低氧模型组和常氧组大鼠的去内皮肺动脉环,观察PKC激活剂PMA0.5μmol/L对肺动脉环的时间-效应曲线以及NF-κB抑制剂PDTC0-1000μmol/L时对PMA诱导肺动脉环反应性改变的浓度-效应曲线。以血管环对10μmol/L盐酸苯肾上腺素的最大反应值为P₀,对PMA和PDTC的反应值以占P₀的百分值表示(%P₀),记录达最大反应值一半时对应的时间t_1/2(min)、峰值持续时间T(min)。结果:低氧组的mPAP及RV/(LV+S)均高于常氧组(P<0.05)。PMA0.5μmol/L作用于血管环:低氧组各时点的张力%P₀均高于常氧组(P<0.05);低氧组t_1/2小于常氧组(P<0.05);低氧组T大于常氧组(P<0.05)。PDTC0-100μmol/L血管环相对张力低氧组均高于常氧组(P<0.05);大于500μmol/L两组血管张力均下降(P<0.05)。结论:低氧可导致去内皮肺动脉环对PMA的反应性增强;PDTC呈剂量依赖性地降低去内皮肺动脉环对PMA的反应性。提示肺动脉平滑肌细胞内PKC－NF-κB生物信号转导途径的变化可能参与低氧性肺动脉高压肺血管反应性异常升高的过程。     

缺血低氧对大鼠心肌产生血管内皮生长因子的影响及其意义

目的:了解缺血低氧刺激与大鼠心肌血管内皮生长因子(VEGF)产生的关系、意义及其可能机制。方法:1.建立Wistar大鼠急性心肌梗塞模型,将28只大鼠随机分为4组,每组7只:A组正常对照;B组急性心肌梗塞1d;C组急性心肌梗塞3d;D组急性心肌梗塞7d。心肌冰冻切片,免疫组化探测VEGF。2.原代培养大鼠心肌细胞随机分组:单纯缺氧组,A:缺氧培养0h;B:缺氧培养6h;C:缺氧培养12h;D:缺氧培养24h;蛋白激酶C(PKC)激动剂波佛酯(PMA)组,A:加入PMA0ng/mL;B:加入PMA10ng/mL;C:加入PMA100ng/mL;D:加入PMA1000ng/mL;均缺氧培养24h;PKC抑制剂chelerythrine(CT)组,A:加入CT0nmol/L;B:加入CT10nmol/L;均缺氧培养24h。免疫组化测定培养心肌细胞中血管内皮生长因子(VEGF),经计算机扫描,图像分析定量。结果:随缺血低氧时间延长,心肌产生VEGF增加,与对照组比较各组均有显著差异,缺血低氧时间与VEGF产生量呈正相关。不同剂量PMA与chelerythrine分别增强及减弱VEGF在缺氧心肌细胞中的表达。结论:缺血低氧强烈刺激心肌产生血管内皮生长因子,缺血心肌通过分泌VEGF对自身具有重要的保护意义。其信号转导途径部分是通过PKC通路实现的。     

芥子酸对高糖诱导下大鼠血管平滑肌细胞增殖和凋亡的影响

目的:探讨芥子酸对高糖诱导下大鼠血管平滑肌细胞(vascular smooth muscle cells,VSMCs)增殖和凋亡的影响及机制。方法:将培养的A7r5细胞随机分组处理,MTT法检测细胞活力,Brd U法检测细胞DNA合成,流式细胞术检测细胞周期进程和细胞凋亡,ELISA检测细胞活性氧簇(reactive oxygen species,ROS)生成,Western blot检测cyclin D1、P21和P27等蛋白的表达,以及蛋白激酶C(PKC)和P38的磷酸化水平。结果:与正常组比较,高糖组细胞活力显著升高,DNA合成加快,细胞周期加快,P21和P27表达降低,cyclin D1表达增加,ROS水平增加,细胞凋亡率降低,p-PKC和p-P38蛋白水平增加(P0.05)。而芥子酸(0.1、1和10μmol/L)处理引起细胞增殖活性降低,DNA合成减弱,细胞周期受阻,P21和P27表达增加,cyclin D1表达降低,ROS水平降低,细胞凋亡率升高,p-PKC和p-P38蛋白水平降低,且呈一定浓度依赖性(P0.05)。P38抑制剂SB203580和PKC抑制剂chelerythrine均显著抑制高糖诱导的PKC/P38活化和细胞活力(P0.05)。结论:芥子酸可通过抑制PKC/P38激活降低高糖诱导的VSMCs增殖,并促进细胞凋亡。     

Activation of store-operated channels by noradrenaline via protein kinase C in rabbit portal vein myocytes

In the present study we have investigated the role of diacylglycerol (DAG) and protein kinase C (PKC) in mediating activation of Ca²⁺-permeable store-operated channels (SOCs) by noradrenaline in rabbit portal vein smooth muscle cells. With cell-attached recording, bath application of noradrenaline, 1-oleoyl-acetyl- sn -glycerol (OAG) and phorbol 12,13-dibutyrate (PDBu) evoked single channel currents. The biophysical properties of these channel currents were similar to those of the channel currents activated by depletion of internal Ca²⁺ stores with cyclopiazonic acid (CPA). The activation of SOCs in cell-attached recording by noradrenaline, OAG, PDBu, CPA and the acetoxymethyl ester form of BAPTA (BAPTA-AM) was markedly inhibited by the PKC inhibitors chelerythrine and RÖ-31-8220. In isolated outside-out patches CPA did not evoke SOCs but noradrenaline stimulated SOC activity, which was reduced by about 90 % by PKC inhibitors. The addition of the serine/threonine phosphatase inhibitors calyculin A and microcystin also stimulated SOCs in isolated outside-out patches. It is concluded that in rabbit portal vein myocytes, noradrenaline activates SOCs via DAG and PKC, possibly by a store-independent mechanism. In addition in this cell type it appears that PKC and phosphorylation may play an important role in stimulating SOC activity in response to depletion of internal Ca²⁺ stores by CPA and BAPTA-AM.     

Direct effects of tolbutamide on mitochondrial function, intracellular Ca2+ and exocytosis in pancreatic β-cells

 Using the whole-cell voltage-clamp method to measure ATP-sensitive K⁺(K_ATP) currents, changes in cell capacitance to measure secretion and microfluorimetry to monitor intracellular Ca²⁺ and mitochondrial function, we have investigated the direct effect of sulphonylureas on exocytosis in pancreatic β-cells. Tolbutamide (100 μM) and 100 nM 4-β-12-phorbolmyristate-13-acetate (PMA), which activates the protein kinase C (PKC) isoforms found in β-cells, potentiated exocytosis in a non-additive manner. These effects were blocked by down-regulation of PKC. Our data support the idea that tolbutamide can potentiate secretion from β-cells via a PKC-dependent pathway. Because PKC and sulphonylureas can modulate the activity of K_ATP channels, we explored whether the above effects are caused by inhibition of this channel. PMA increased whole-cell K_ATP currents but did not affect their sensitivity to tolbutamide. Down-regulation of PKC affected neither the magnitude nor the tolbutamide sensitivity of the K_ATP current. Both tolbutamide and the mitochondrial uncoupler FCCP (1 μM) mobilized intracellular Ca²⁺ and prolonged Ca²⁺ transients elicited by cholinergic mobilization of intracellular Ca²⁺ stores. Tolbutamide (0.1–0.5 mM), like FCCP, depolarized the mitochondrial membrane potential and activated K_ATP currents. We suggest that sulphonylureas can directly potentiate exocytosis by impairing mitochondrial function and Ca²⁺ handling, which ultimately leads to activation of Ca²⁺-dependent enzymes such as PKC. Received: 1 September 1998 / Received after revision: 9 November 1998 / Accepted: 10 November 1998     

PKC/Raf-1/NF-κB信号通路在低氧诱导大鼠单核细胞表达TNF-α中的作用

目的：研究PKC/Raf-1/NF-κB信号通路在低氧诱导大鼠外周血单核细胞（PBMCs）肿瘤坏死因子α（TNF-α）表达中的作用，探讨低氧与全身炎症反应综合征(SIRS)的关系，为进一步研究老年多器官功能障碍综合征(MODSE)的肺启动机制奠定基础。方法:采用明胶法分离大鼠外周血单核细胞，分为chelerythrine+低氧组、forskolin+低氧组和单纯低氧组。Chelerythrine+低氧组和forskolin+低氧组细胞在低氧前分别予10 μmol/L chelerythrine和50 μmol/L forskolin预处理。然后各组均于低氧条件下（3 % O2, 5 % CO2, 92 % N2）培养0、1、3、6、9、12、24 h后，收集细胞及培养液上清，分别采用PKC、Raf活性检测试剂盒、电泳迁移分析法（EMSA）、逆转录PCR（RT-PCR）和酶联免疫吸附试验（ELISA）检测PKC、Raf-1、NF-κB活性及TNF-α表达量。结果:低氧1-9 h，PKC、Raf-1活性、NF-κB结合活性及TNF-α表达量显著高于正常对照组（P<0.01）。低氧后1-24 h，PKC、Raf-1活性、NF-κB结合活性与TNF-α mRNA和蛋白表达水平间呈显著正相关（P<0.01，P<0.05）。10 μmol/L chelerythrine可显著抑制低氧诱导的PKC、Raf-1、NF-κB活性升高和TNF-α表达。50 μmol/L forskolin可显著抑制低氧诱导的Raf-1、NF-κB活性升高及TNF-α表达。结论:低氧可显著增强大鼠外周血单核细胞的PKC、Raf-1活性及NF-κB结合活性,并可诱导其产生大量的促炎症因子TNF-α，这些变化可能与急性呼吸窘迫综合征（ARDS）时血浆中大量促炎症因子持续存在密切相关。     

Diverse properties of store-operated TRPC channels activated by protein kinase C in vascular myocytes

In vascular smooth muscle, store-operated channels (SOCs) contribute to many physiological functions including vasoconstriction and cell growth and proliferation. In the present work we compared the properties of SOCs in freshly dispersed myocytes from rabbit coronary and mesenteric arteries and portal vein. Cyclopiazonic acid (CPA)-induced whole-cell SOC currents were sixfold greater at negative membrane potentials and displayed markedly different rectification properties and reversal potentials in coronary compared to mesenteric artery myocytes. Single channel studies showed that endothelin-1, CPA and the cell-permeant Ca(2+) chelator BAPTA-AM activated the same 2.6 pS SOC in coronary artery. In 1.5 mM [Ca(2+)](o) the unitary conductance of SOCs was significantly greater in coronary than in mesenteric artery. Moreover in 0 mM [Ca(2+)](o) the conductance of SOCs in coronary artery was unaltered whereas the conductance of SOCs in mesenteric artery was increased fourfold. In coronary artery SOCs were inhibited by the protein kinase C (PKC) inhibitor chelerythrine and activated by the phorbol ester phorbol 12,13-dibutyrate (PDBu), the diacylglycerol analogue 1-oleoyl-2-acetyl-sn-glycerol (OAG) and a catalytic subunit of PKC. These data infer an important role for PKC in activation of SOCs in coronary artery similar to mesenteric artery and portal vein. Anti-TRPC1 and -TRPC5 antibodies inhibited SOCs in coronary and mesenteric arteries and portal vein but anti-TRPC6 blocked SOCs only in coronary artery and anti-TRPC7 blocked SOCs only in portal vein. Immunoprecipitation showed associations between TRPC1 and TRPC5 in all preparations but between TRPC5 and TRPC6 only in coronary artery and between TRPC5 and TRPC7 only in portal vein. Finally, flufenamic acid increased SOC activity in coronary artery but inhibited SOCs in mesenteric artery and portal vein myocytes. These data provide strong evidence that vascular myocytes express diverse SOC isoforms, which are likely to be composed of different TRPC proteins and have different physiological functions.     

Effect of phorbol 12,13-dibutyrate on smooth muscle tone in rat stomach fundus.

We investigated the effects of phorbol 12,13-dibutyrate (PDBu), a typical protein kinase C (PKC) activator, on smooth muscle tone in the rat stomach fundus. In 5-hydroxytriptamine (5-HT)-precontracted stomach fundus strips, PDBu induced dose-dependent relaxation, but 4alpha-phorbol 12,13-didecanoate, a phorbol ester that does not activate PKC, did not induce relaxation. A PDBu-induced dose-dependent relaxation was also observed in strips precontracted with platelet-activating factor (PAF), carbachol, or 60 mM K+. In stomach fundus strips pretreated with PDBu, the contractile responses to 5-HT and PAF were completely blocked, but those induced by carbachol and endothelin-1 (ET-1) were only partially inhibited. In stomach fundus strips preincubated with carbachol in Ca2+-free medium, the Ca2+-induced contraction was decreased by preincubation with PDBu. In strips preincubated with 5-HT, PAF, or ET-1 in Ca2+-free medium, Ca2+-induced contractions were greatly inhibited by pretreatment with PDBu. These results suggest that in rat stomach fundus strips, PDBu-induced relaxation is mediated by activation of PKC. We speculate that a major factor mediating the relaxant action of PDBu in rat stomach fundus smooth muscle is represented by a reduction in Ca2+ influx via an inhibition of Ca2+ channels.     

参与失血性休克血管钙敏感性调节的信号分子

目的：观察Rho-激酶、PKC、PKG对失血性休克大鼠血管钙敏感性的调控作用。 方法： 取失血性休克大鼠肠系膜上动脉，利用离体血管环张力测定技术，用去极化状态下(120 mmol/L K+)血管环对梯度浓度Ca2+的收缩力反映钙敏感性，观察Rho-激酶激动剂血管紧张素Ⅱ（Ang-Ⅱ）、Rho-激酶抑制剂fasudil、PKC激动剂PMA、PKC拮抗剂staurosporine、PKG激动剂8Br-cGMP和PKG拮抗剂KT-5823对失血性休克血管钙敏感性的影响。 结果： Ang-Ⅱ、PMA、KT-5823可增高失血性休克血管的钙敏感性，表现为Ca2+的量效曲线明显左移，在Ca2+（3×10-2 mol/L）水平，Emax分别为0.630 g/mg、0.595 g/mg、0.624 g/mg，均明显高于休克组的0.377 g/mg(P<0.05，P<0.01)；fasudil、staurosporine、8Br-cGMP可降低失血性休克血管的钙敏感性，表现为Ca2+的量效曲线明显右移，在Ca2+（3×10-2 mol/L）水平，Emax分别为0.242 g/mg、0.230 g/mg、0.256 g/mg，均显著低于休克组(P<0.05，P<0.01)。 结论： Rho-激酶、PKC、PKG对失血性休克大鼠血管钙敏感性有调节作用，Rho-激酶、PKC可上调钙敏感性，PKG可下调钙敏感性。     

Effects of phorbol esters on excitation-contraction coupling and protein kinase C activity of frog twitch muscle fibers

 By recording the calcium transients evoked by voltage-clamp depolarizing pulse with arsenazo III as a calcium indicator, it has been shown that 1 μmol/l phorbol 12,13-dibutyrate (PDBu), a protein kinase C (PKC) agonist, causes a transient potentiation and then a depression of the calcium transients of twitch muscle fibers in frogs. PDBu also produces an initial translocation and activation of PKC, which is followed by a down-regulation. To find out whether the effect of PDBu on the calcium transients depends on PKC, a correlated study of the effect of phorbol esters on calcium transients and PKC activity was performed. The calcium transients and PKC activity were similarly affected by PDBu in ordinary and cold-accommodated frogs, but the effects occurred more quickly in the latter. However, they still changed in parallel as in ordinary frogs. 1 or 10 μmol/l, 4-α-phorbol, a PKC-inactive analogue of phorbol ester, caused a partial depression of the calcium transients in cold-accommodated frogs, while PKC activity was not affected. Moreover, the transient potentiation of the calcium transients induced by 1 μmol/l PDBu could be antagonized by the PKC inhibitors 10 μmol/l chelerythrine chloride or 10 μmol/l polymyxin B (PMB). All these results suggest that: (1) the transient potentiation of calcium transients induced by PDBu is caused by activation of PKC; (2) phorbol ester can depress the calcium transients by a mechanism that is independent of PKC. Received: 25 September 1998 / Received after revision: 14 December 1998 / Accepted: 19 January 1999     

PKC在成年大鼠脊髓背角C-纤维诱发电位长时程增强的诱导和维持中的作用

目的：探讨蛋白激酶C (PKC) 在大鼠脊髓背角C-纤维诱发电位长时程增强（LTP）的诱导和维持中的作用。方法： 细胞外记录技术在脊髓腰膨大部记录背角浅层神经元C-纤维诱发电位。 结果：(1) PKC的选择性抑制剂chelerythrine（200 μmol/L）或G 6983（100 μmol/L）对脊髓背角C-纤维诱发电位的基础电位没有影响，但可完全阻断脊髓背角LTP的诱导。(2) Chelerythrine或G 6983呈时间依赖性翻转脊髓背角LTP。在LTP 诱导后15 min，脊髓局部给予chelerythrine（200 μmol/L）后，LTP逐渐降低，于给药后70 min降至对照水平；而G 6983（100 μmol/L）产生同chelerythrine相似的效应，在用药后110 min，LTP降至对照水平。但同样浓度的chelerythrine或G 6983在LTP 诱导后3 h，均不能翻转业已建立的LTP。结论： PKC参与脊髓背角C-纤维诱发电位LTP的诱导和早期维持，而不影响晚期LTP的维持。