适合膜片钳试验的一种外周血嗜酸性粒细胞分离法

目的 建立一种从人群外周血中分离出适合膜片钳试验的外周血嗜酸性粒细胞(EOS)分离方法,并在分离的细胞上观察其K⁺-ca^2-通道特性。方法 采用改良的不连续密度梯度法分离EOS,用膜片钳单通道记录法记录K⁺-ca^2-通道电流。结果 外周血EOS的回收率为(48.2±6.9)%、存活率>99%、纯度为(90.5±1.6)%。EOS形态完整,可检测到其膜上的K⁺-ca^2-通道。结论 该法能短时间内从外周血中分离出高存活率、无细胞损伤的EOS,是一种适于膜片钳试验中分离外周血EOS的方法。     

维生素K3通过钙依赖钾通道影响豚鼠结肠平滑肌收缩

目的 探讨维生素K3松弛胃肠道平滑肌的机制.方法 采用TD-112S型传感器测量豚鼠结肠平滑肌肌条收缩幅值、频率;用EPC10膜片钳放大器测量全细胞模式下细胞膜钙依赖钾电流[IK(ca)].结果 浓度为40、100、400、800 μmol/L的维生素K3作用后,肌条收缩频率分别为对照组的79%±4%,58%±5%,33%±4%,12%±3%(均P＜0.01).收缩强度分别为对照组的77%±10%,54%±7%,30%±6%,11%±4%(均P＜0.01).在+60 mV,I K(ca)值分别为对照组的120%±18%,149%±12%,197%±19%,223%±14%(均P＜0.01).结论 维生素K3能抑制平滑肌自发性收缩频率和强度,增强细胞膜IK(ca),且呈浓度依赖性.其机制与钙依赖钾通道的激活,促进钾离子外流有关.     

改良的适合膜片钳试验的血管内皮细胞处理方法

目的 建立一种简便的、适合膜片钳试验的人脐静脉内皮细胞(ECV304)处理方法,并在培养的细胞上观察其钙激活钾通道(Kca)特性.方法 采用改良的内皮细胞培养方法,用单通道记录法记录内皮细胞Kca电流.结果 内皮细胞在光镜下呈梭形,并可以检测到细胞膜上的Kca电流.结论 本方法改良了传统的内皮细胞培养方法,能在较短时间内完成膜片钳通道记录,是一种适合膜片钳试验的处理方法.     

过氧化物诱导LO2细胞凋亡时Fas mRNA表达及Ca^2＋流变化的单 …

探讨过氧化物所致肝细胞凋亡时Ｆａｓ基因表达与Ｃａ＾２＋流变化的相互关系。方法应用全细胞膜片错单细胞逆转录聚合酶链反应技术进行Ｈ２Ｏ２诱导人类正常肝细胞ＬＯ２细胞ＦａｓｍＲＮＡ表达的单细胞分析,应用全细胞膜片错显微荧光单细胞胞浆游离钙浓度测量技术、流式细胞术、扫描电镜观察同期瞬时Ｃａ＾２＋流变化及早期凋亡（Ａｎｎｅｘｉｎ－Ｖ）细胞指数和细胞膜变化。结果Ｈ２Ｏ２作用２ｈ单个ＬＯ２细胞电泳图分析可见Ｆａ     

匹那地尔对大鼠缺血心肌钙调控的作用

目的 :探讨大鼠缺血心肌再灌注 (I- R)损伤的钙调控机制及匹那地尔对心肌 I- R损伤的保护作用机理。方法 :取 SD大鼠 ,心室肌细胞酶解分离 ,心肌细胞静息 1～ 2 h后随机分为 4组 :对照组、高钾停搏液组、匹那地尔强化组、格列苯脲拮抗组。 4组细胞在 2 4℃下保存 2 h后 ,复氧、复灌 2 0 min同时测定 [Ca2 + ]i 瞬态变化、肌浆网内贮钙释放功能。结果 :经匹那地尔强化处理的心肌细胞在 I- R过程中 [Ca2 + ]i 瞬态变化恢复率明显高于高钾停搏液组 (90 .2 7%～ 95 .5 7% vs6 7.0 5 %～ 80 .11% ,P<0 .0 1)。肌浆网内贮钙释放能力 (173.15 %± 2 6 .0 1% )明显高于高钾停搏液组 (112 .0 0 %± 16 .93% ) (P<0 .0 1)。经匹那地尔强化处理的心肌细胞在咖啡因诱导的钙释放后 ,胞内钙离子浓度从高水平回复到舒张末静息水平的时间为 (3.2 0± 0 .71) ms,显著短于高钾停搏液组 (3.93± 0 .4 6 ) ms(P<0 .0 5 )和对照组 (4 .6 8± 0 .77) ms(P<0 .0 1)。结论 :匹那地尔通过肌浆网和细胞膜 Na+ /Ca2 +交换体功能来调节钙瞬态变化 ,减少细胞内钙超载使心肌细胞在 I- R过程中保持较好的钙调控功能。     

原代培养猪冠状动脉平滑肌的电压依赖和钙激活钾通道

目的：研究原代培养的猪冠状动脉平滑肌电压依赖性和钙激活外向钾通道的特性。方法：离子通道电流采用膜片钳技术进行记录。结果：在内面向外式膜片构型,当膜内外K^ 浓度梯度类似生理状态时,该通道单位电导值约为100pS,而当膜内外K^ 浓度为对称的140mM浓度时,该通道单位电导值约270pS。其平均电流显示该通道具时间和电压依赖性激活特性,而无任何时间和电压依赖性失活特性。另外,通道的开放时间常数和开放概率随除极及胞内Ca^2 的增加而显著增加。通过用EGTA降低胞浆内Ca^2 浓度,可使外向电流抑制。动力学分析显示通道激活时存在一种开放状态和至少两种关闭状态。四乙胺（TEA）可在胞外侧阻断该电流,但高达15mM的4－氨基吡啶（4－AP）在胞内外都对通道无影响。在全细胞构型,对细胞膜进行除极可引出宏观外向电流。随着细胞的除极,该电流的激活时间常数逐渐缩短,并显示快速激活动力学特性。结论：在原代培养的猪冠状动脉平滑肌上存在有电压依赖和Ca^2 激活的K^ 选择性离子通道。该类通道具有非常高的单位电导值,除极时快速开放,对胞内Ca^2 高度敏感,但无失活等特性。     

otassium channels in airway smooth muscle and airway hyperreactivity in asthma

Ourknowledgeofthephysiologyofionchannelshasincreasedtremendouslyduringthepast20yearsbecauseoftheadvancesofthesingle channel recordingandmolecularcloningtechniques.More than50differentidentifiedpotassiumchannelshave alreadybeenfound.1,2Theyaredistributed ubiquitouslyinwidevarietyofcellsincludingairway smoothmuscle(ASM)cellsandinflammatorycells inairwaysuchaseosinophils,basophils,macrophagesandsoon.3SeveraltypesofK+channelshavebeenidentifiedinASMcells,e.g.,a large conductance,voltgage depende…     

Characteristics of single Ca2+channel kinetics in feline hypertrophied ventricular myocytes

目的　慢性压力负荷导致的心肌肥厚所伴有的动作电位时程的延长可能与L型钙流失活延迟有关。本文的目的是探索左室高血压所致的家猫肥厚心肌的单通道L型钙流的特征 ,以及在动作电位延长中的作用。方法　应用膜片钳技术研究正常和压力负荷所致的肥厚家猫心肌单通道L型钙流的特征。左室高血压模型用部分结扎降主动脉的方法。结果　从 - 40mV去极化到 0mV时 ,正常心肌和肥厚心肌的单通道L型钙流的振幅分别为 1 0 2± 0 0 3pA和1 0 5± 0 0 3pA ,斜率电道分别为 2 6 2± 1 0pS和 2 5 8± 0 9pS ,两者相比均无差别。但脉冲终末部分的平均振幅 ,肥厚心肌明显大于正常心肌。通道开放时间直方图分析表明 ,正常心肌细胞的开放时间分布呈单指数曲线 ,而肥大心肌细胞为双指数曲线。肥大心肌的平均开放时间明显长于正常心肌细胞。结论　左室压力负荷所致的肥大细胞的动作电位时程延长与L型钙流的失活时间延迟有关。     

产前应激对子代大鼠海马CA3区神经元高电压激活Ca2+通道动力学特征的影响

目的探讨产前应激对子代大鼠海马CA3神经元高电压激活(HVA)钙通道动力学特征的影响。方法给予孕鼠束缚应激,急性分离子代海马CA3神经元,应用全细胞膜片钳技术,研究产前应激对子代大鼠海马CA3区神经元高电压激活Ca2 通道的影响。结果产前应激增加了子代海马CA3神经元高电压激活钙电流幅值、电流面积,而未改变其电导-电压关系、稳态失活动力学、时间到峰等指标。对照组和产前应激组子代海马CA3神经元高电压激活最大钙电流幅值分别为(-40.89±0.31)pA/pF和(-49.44±0.37)pA/pF(P<0.01)。最大电流面积分别为(106.81±4.20)nA*ms和(133.49±2.59)nA*ms(P<0.01)。结论在胎儿发育的关键时期,给予母体应激,对子代海马神经元离子通道产生持续的影响。     

慢性乙型重型肝炎患者肝组织中浸润淋巴细胞中免疫活性细胞的研究

目的 明确慢性乙型重型肝炎（简称慢重肝）患者肝内浸润的淋巴细胞（LILs）及外周血中免疫活性细胞的频率,并对其进行对比分析,以明确它们的异同以及在慢重肝发病机理中的作用。方法 通过毛玻璃研磨加自然沉降肝细胞的方法,对11例慢重肝接受肝移植患者的LILs进行提取、分离。通过流式细胞仪测定慢重肝患者LILs及外周血中免疫活性细胞的频率并行对比分析,同时与正常人LILs及外周血中免疫活性细胞的频率进行对比分析。结果 （1）慢重肝患者LILs中CD4^＋T淋巴细胞及B细胞的频率分别为17％±6％及3．0％±1．0％,明显低于外周血中各自的频率,分别为32％±8％及21．4％±12．2％（均P〈0．01）,而CD8^＋T淋巴细胞、NK及NKT细胞的频率分别为38％±13％、34％±18％及10％±4％,明显高于外周血中各自的频率,分别为26％±6％、15％±9％及6％±4％（均P〈0．05）;（2）与正常对照相比,LILs中CD3^＋及CD4^＋T淋巴细胞明显要高（P〈0、05或P〈0、01）,而NK细胞及NKT细胞要低些;（3）与正常对照相比,慢重肝患者uIJs与外周血淋巴细胞之比,CD3^＋、CD4^＋、CD8^＋T淋巴细胞有更高的比值（CD4^＋T淋巴细胞P〈0、01）,B细胞及NKT细胞有更低的比值（P〈0．01或P〈0、05）。结论 肝脏内大量免疫活性细胞的浸润,尤其是CD4^＋、CD8^＋T淋巴细胞、NK细胞的大量浸润对于慢重肝的发病可能起重要的作用。     

铁对白细胞介素-2舒血管效应的调制作用

目的 :研究微量元素铁对白细胞介素 - 2 (IL- 2 )舒血管效应的调制作用及其机理。方法 :采用离体主动脉环灌流模型 ,在苯肾上腺素 (1μmol/ L)预收缩基础上 ,测定经柠檬酸铁胺 (FAC)处理后 IL- 2对血管张力的变化 ;用分光光度法测定血管一氧化氮合酶 (NOS)活性。结果 :FAC(0 .1～ 10μmol/ L )孵育 30 min后对血管的张力无影响 ,却能浓度依赖性的抑制 IL - 2 (1～ 10 0 0 U/ ml)的舒血管效应 (P<0 .0 5～ 0 .0 1)。 IL - 2 (1、10、10 0、10 0 0 U/ ml)单独作用后的血管张力分别为加药前的 (78.4 7± 4 .31) %、(6 6 .86± 5 .5 5 ) %、(5 2 .6 2± 4 .5 1) %和 (4 2 .39± 4 .2 7) %。10 μmol/ L FAC预处理后再加 IL- 2 ,血管张力为 (89.81± 1.94 ) %、(86 .13± 3.11) %、(77.16± 5 .6 6 ) %和 (6 8.76± 5 .6 9) %。L-精氨酸 (1mmol/ L)孵育取消了 FAC对 IL- 2舒血管效应的抑制作用。IL- 2 (10 0 0 U/ ml)使 NOS的活性从 (9.86± 0 .5 4) U/ ml prot显著增高为 (2 2 .10± 1.87) U/ ml prot。FAC(10 μmol/ L)单独孵育 30 min NOS的活性为 (10 .5 9± 0 .5 9) U/ ml prot,但是 FAC预处理再加 IL - 2后 ,NOS活性显著降低为 (15 .71± 0 .89) U/ ml prot;高钙 (2 .5 mmol/ L )预处理 ,不改变 FAC对     

哮喘气道炎症与Ⅰ型及Ⅱ型T辅助细胞的演变

目的　探讨T淋巴细胞的增殖和分化在哮喘气道炎症过程中的变化。方法　选择初治未经皮质激素治疗的中重度急性加重期哮喘患者 2 0例 ,缓解期患者 15例 ,正常对照组 10名。SD大鼠 16只 ,按随机表法分为实验组和对照组 ,每组 8只 ,实验组给予卵清蛋白致敏激发。采用流式细胞分析技术检测哮喘患者及大鼠外周血分泌干扰素γ(IFN γ)的CD4 、CD8 细胞及分泌白细胞介素 4(IL 4 )的CD4 细胞的百分数。结果　 (1)哮喘急性加重期患者外周血分泌IFN γ的CD4 细胞(30 %± 10 % )和CD8 细胞 (4 2 %± 15 % )均高于缓解期患者 (分别为 2 0 %± 8% ,P <0 0 1;30 %±10 % ,P <0 0 1)和正常人 (分别为 18%± 8% ,P <0 0 1;2 4 %± 9% ,P <0 0 1) ;分泌IL 4的CD4 细胞 (4 2 %± 1 6 % )也显著高于缓解期患者 (2 0 %± 0 8% ,P <0 0 1)及正常人 (1 9%± 0 9% ,P <0 0 0 1)。缓解期患者与正常人之间上述各参数差异无显著意义。 (2 )哮喘模型大鼠外周血分泌IFN γ的CD4 细胞在激发 2h后开始升高 (5 7%± 1 6 % ) ,并在 10h时达到高峰 (9 9%± 4 4 % ) ,以后逐渐下降 ;分泌IFN γ的CD8 细胞在激发后 2h开始增高 (11 5 %± 5 1% ) ,并于 10h达到高峰 (38 7%± 6 3% ) ,以后逐渐下降 ;分泌IL 4的CD4     

Effects of Chinese herbs on multiple ion channels in isolated ventricular myocytes

Background Shensong Yangxin (SSYX) is one of the compound recipe of Chinese materia medica. This study was conducted to investigate the effects of SSYX on sodium current (I(Na)), L-type calcium current (I(Ca,L)), transient outward potassium current (I(to)), delayed rectifier current (I(K)), and inward rectifier potassium currents (I(K1)) in isolated ventricular myocytes. Methods Whole cell patch-clamp technique was used to study ion channel currents in enzymatically isolated guinea pig or rat ventricular myocytes. Results SSYX decreased peak I(Na) by (44.84±7.65)% from 27.21±5.35 to 14.88±2.75 pA/pF (n=5, P&lt;0.05). The medicine significantly inhibited the I(Ca,L). At concentrations of 0.25, 0.50, and 1.00 g/100 ml, the peak I(Ca,L) was reduced by (19.22±1.10)%, (44.82±6.50)% and (50.69±5.64)%, respectively (n=5, all P&lt;0.05). SSYX lifted the I-V curve of both I(Na) and I(Ca,L) without changing the threshold, peak and reversal potentials. At the concentration of 0.5%, the drug blocked the transient component of I(to) by 50.60% at membrane voltage of 60 mV and negatively shifted the inactive curve and delayed the recovery from channel inactivation. The tail current density of I(K) was decreased by (30.77±1.11)% (n=5, P&lt;0.05) at membrane voltage of 50 mV after exposure to the medicine and the time-dependent activity of I(K) was also inhibited. Similar to the effect on I(K), the SSYX inhibited I(K1) by 33.10% at the test potential of –100 mV with little effect on reversal potential and the rectification property. Conclusions The experiments revealed that SSYX could block multiple ion channels such as I(Na) I(Ca,L), I(k), I(to) and I(K1), which may change the action potential duration and contribute to some of its antiarrhythmic effects.     

法乐四联症儿童肥厚右心室细胞瞬间外向钾电流的研究

目的观察压力增高导致的人肥厚心室组织离子通道的特性.方法应用酶解分离技术从法乐四联症(F4)患儿的心脏右室得到单个细胞,应用膜片钳全细胞记录技术观察了细胞Ito1的特征.结果将钙电流阻断后,去极化至-20mV～+60mV时均可记录到Itn1,激活后电流衰减速度不随去极化程度的增强而改变,在0、20、40、60mV时分别为123ms±6ms、131ms±10ms、122ms±6ms、122ms±6ms,去极化至60mV时的电流密度为4.7pA/pF±0.8pA/pF,半数最大激活电位为4.1mV±2.8mV,半数最大失活电位出现在-41mV±4mV,失活后再激活的恢复时间常数为83ms±4ms.这种电流可被10mM4-AP基本抑制.结论肥厚的人右室细胞存在Itn1,通道动力学特征与成人心房肌细胞类似.     

不同潮气量机械通气大鼠血清对血管内皮细胞钙激活钾通道的影响

目的:研究不同潮气量机械通气大鼠血清对血管内皮细胞钙激活钾通道(KCa通道)的影响.方法:健康雄性SD大鼠随机分为A组(麻醉后不做任何处)和B、C组(麻醉后行气管切开插管并分别给予不同潮气量(VT)的机械通气4h.B组VT10mL/kg,C组40 mL/kg),通气结束后取各组大鼠血清,分别刺激已培养好的人脐静脉内皮细胞(ECV304)30 min,利用细胞贴附式膜片钳观察KCa通道的变化.结果:B、C组内皮细胞KCa通道开放率明显上升,且以C组最为明显.结论:不同VT机械通气大鼠血清对ECV304 KCa通道的开放、关闭具有一定的影响.     

Na+/Ca2+ exchanger current and K+ current remodeling in midmyocardial cells of hypertrophic left ventricle]

OBJECTIVE: To investigate the characteristics of Na+/Ca2+ exchanger current (INa+ /Ca2+) and K+ current remodeling in midmyocardial cells of hypertrophic left ventricle for understanding the ionic basis of arrhythmia of the hypertrophic heart. METHODS: Twenty New Zealand rabbits were divided equally into normal control group and operation group, and in the latter, left ventricular hypertrophy was induced in the rabbits by partial ligation of the abdominal aorta. Action potentials, INa+/Ca2+, slowly activating delayed rectifier K+ current (IKs) and rapidly activating delayed rectifier K+ current (IKr) were recorded in the two groups by using whole-cell patch-clamp technique. RESULTS: At the basic cycle length of 2 s, 90% action potential duration (APD90) in control and operation groups was 522.0+/-19.5 ms (n=6) and 664.7+/-32.7 ms (n=7) respectively; at the testing potential of +40 mV, outward INa+/Ca2+ density in the two groups was 0.94+/-0.11 pA/pF (n=9) and 1.30+/-0.11 pA/pF (n=8) respectively; the testing potential of -100 mV elicited inward INa+/Ca2+ density of 0.40+/-0.05 pA/pF (n=9) and 0.56+/-0.02 pA/pF (n=8) respectively. The testing potential of +50 mV induced IKs tail current density of 0.26+/-0.03 pA/pF (n=8) and 0.17+/-0.01 pA/pF (n=9), and IKr tail current density of 0.34+/-0.02 pA/pF (n=8) and 0.23+/-0.02 pA/pF (n=9) respectively. Statistically significant differences were identified between the control and operation groups in all the above indices measured. CONCLUSION: The characteristics of electrical remodeling changes in midmyocardial cells of hypertrophic left ventricle, exhibited by prolonged action potential, up-regulated INa+/Ca2+ and down-regulated IKs and IKr.     

华蟾素对大鼠胸主动脉的缩血管作用及其机制

目的:研究中成药华蟾素对大鼠离体胸主动脉环的作用及其机制。方法:采用大鼠离体胸主动脉灌流模型,观察华蟾素对血管张力的影响。结果:华蟾素(2.5、5.0、7.5、10.0 g/L)浓度依赖性地收缩去内皮的大鼠胸主动脉环,收缩幅度分别为(16.3±3.39)%、(52.5±7.70)%、(60.9±8.84)%、(69.2±11.34)%,显著高于内皮完整的大鼠胸主动脉环收缩幅度[(6.2±2.07)%、(14.7±4.91)%、(17.6±5.86)%、(20.3±6.78)%](P<0.01);在无Ca2 液中,10.0 g/L华蟾素对去内皮主动脉环的收缩幅度[(7.1±0.79)%]显著低于有Ca2 液中的收缩幅度[(78.1±4.32)%](P<0.01);维拉帕米(1-0 7m o l/L,V er)预处理可消除10.0 g/L华蟾素的缩血管作用(P<0.01);一氧化氮合酶抑制剂L-NAM E(1-0 4m o l/L)预处理内皮完整的主动脉环,可增强10.0 g/L华蟾素的缩血管作用(P<0.01)。结论:华蟾素对大鼠离体胸主动脉有收缩作用,其缩血管机制与其促使细胞外Ca2 经电压依赖性钙通道内流进入血管平滑肌细胞有关;同时,华蟾素作用于血管内皮细胞,引起血管舒张因子一氧化氮的释放,部分抵消其缩血管效应。     

TNF-α的心肌负性肌力作用机制研究

目的 :探讨肿瘤坏死因子α(TNF-α)对心肌的负性肌力作用机制。方法 :采用离体大鼠乳头肌张力测定 ,细胞内双波长钙荧光检测和 ATP酶分析方法。结果 :1TNF-α抑制大鼠右心室乳头肌的收缩力 ,2 0 U/ ml和 2 0 0U/ ml TNF-α灌流 10 min后 ,乳头肌收缩力分别减小到对照的 91%和 76 % (P均 <0 .0 1) ;2 TNF-α处理后对心肌细胞钙瞬态变化幅度无明显影响 (0 .97± 0 .0 5 vs0 .95± 0 .0 7,P>0 .0 5 ) ;3TNF- α明显抑制肌浆网 Ca2 + - ATPase活性 ,平均抑制率达到 2 0 % ;4 TNF- α拮抗肌浆网 Ca2 + - ATPase对底物中不同水平的 Ca2 +和 ATP的正反应性 ;5TNF- α对肌膜 Ca2 + - ATP酶和 Na+ / K+ - ATP酶活性无明显抑制作用。结论 :TNF- α抑制心肌收缩力的负性肌力作用机制可能部分与心室肌浆网 Ca2 + - ATP酶活性下降有关 ,而与膜上的 Ca2 + - ATP酶和 Na+ / K+ - ATP酶活性无关。     

EFFECTS OF THE HOE 694 ON TRANSIENTINWARD CURRENT AND NA＋－ CA2＋ EXCHANGE IN GUINEA PIG CARDIOMYOCYTES

OBJECTIVE: To determine the effects of HOE 694, a new and potent Na(+)-H+ exchanger blocker, on transient inward current (It(i)) and Na(+) - Ca(2+) exchange during hypoxia-reoxygenation in guinea pig cardiomyocytes. METHODS. Cardiomyocytes were isolated from adult guinea pig ventricle. Experiment was performed in an experimental chamber that allowed the cells to be exposed to a sufficiently low O2 pressure. The cells were subjected to hypoxia and reoxygenation. The ionic currents were studied with patch clamp technique. RESULTS: In the absence of HOE 694, hypoxia-reoxygenation induced It(i) in 12 of 15 experiments; but in cardiomyocytes pretreated with HOE 694 (10 approximately 50 micro mol/L), the incidence of It(i) observed during reoxygenation was reduced to 5 of 11 experiments and 3 of 10 experiments, P < 0.05 vs control respectively. The Na(+) - Ca(2+) exchange current was unaffected by HOE 694 under normoxic condition. However, when cells were pretreated with 10 micromol/L HOE 694 for 10 min, then subjected to hypoxia condition, the Na(+) - Ca(2+) exchange current significantly inhibited. CONCLUSIONS: Blockade of the Na(+)-H+ exchange by HOE 694 could reduce Ca(2+) overload upon hypoxia-reoxygenation, and inhibition of Na(+) - H+ exchange may also indirectly decrease Na(+) - Ca(2+) exchange activity during hypoxia.     

Ionic mechanisms of a novel neurotoxin from the sea anemone Anthopleura sp. in rat ventricular myocytes.

OBJECTIVE: To determine the ionic mechanisms of a novel neurotoxin rhk2a obtained from the sea anemone Anthopleura sp. in rat ventricular myocytes. METHODS: Whole-cell patch-clamp recording technique was used to record the sodium, calcium, and sodium-calcium exchange currents (I(Na), I(Ca, L), and I(Na-Ca), respectively) in the isolated single rat ventricular myocytes with or without rhk2a treatment. RESULTS: The current-voltage (I-V) relationship for whole-cell I(Na) in the non-treated and rhk2a-treated (at the dose of 1 micromol/L) myocytes showed no significant difference (P>0.05), but the time constants for inactivation (tau(h)) were significantly greater (P<0.05) for the treated cells over the entire course of the experiment, while the time constants for activation (tau(m)) exhibited no significant difference between the two cells. The inactivation curve of I(Na) of rhk2a-treated cells was similar to that of the non-treated cells, as with the I-V relationship for whole-cell L-type calcium current (I(Ca, L) and I(Na-Ca)). CONCLUSIONS: Delayed inactivation of Na(+) channel plays an important role in the positive inotropic effect of rhk2a, possibly resulting from the alteration in Na(+) channel kinetics induced by rhk2a. rhk2a does not directly affect I(Ca, L), or I(Na-Ca).