Inhibitory Effects of Blockage of Intermediate Conductance Ca^(2+) -Activated K^+ Channels on Proliferation of Hepatocellular Carcinoma Cells

The roles of intermediate conductance Ca2＋-activated K＋ channel （IKCal） in the pathogene- sis of hepatocellular carcinoma （HCC） were investigated. Immunohistochemistry and Western blotting were used to detect the expression of IKCal protein in 50 HCC and 20 para-carcinoma tissue samples. Real-time PCR was used to detect the transcription level of IKCal mRNA in 13 HCC and 11 para-carcinoma tissue samples. The MTT assay was used to measure the function of IKCal in human HCC cell line HepG2 in vitro. TRAM-34, a specific blocker of IKCal, was used to intervene with the function of IKCal. As compared with para-carcinoma tissue, an over-expression of IKCal protein was detected in HCC tissue samples （P〈0.05）. The mRNA expression level of IKCal in HCC tissues was 2.17 times higher than that in para-carcinoma tissues. The proliferation of HepG2 cells was suppressed by TRAM-34 （0.5, 1.0, 2.0 and 4.0 pxnol/L） in vitro （P〈0.05）. Our results suggested that IKCal may play a role in the proliferation of human HCC, and IKCal blockers may represent a potential therapeutic strategy for HCC.

Relationship of Intracellular Free Ca^(2+) Concentration and Calcium-activated Chloride Channels of Pulmonary Artery Smooth Muscle Cells in Rats under Hypoxic Conditions

To investigate the relationship between intracellular free Ca^2＋ concentration （[Ca^2＋ ]i ） and calcium-activated chloride （Clca） channels of pulmonary artery smooth muscle cells （PASMCs） in rats under acute and chronic hypoxic conditions, acute hypoxia-induced contraction was observed in rat pulmonary artery by using routine blood vascular perfusion in vitro. The fluorescence Ca^2＋ indicator Fura-2/AM was used to observe [Ca^2＋ ]i of rat PASMCs under normal and chronic hypoxic condition. The effect of Clca channels on PASMCs proliferation was assessed by MTT assay. The Clca channel blockers niflumic acid （NFA） and indaryloxyacetic acid （IAA-94） exerted inhibitory effects on acute hypoxia-evoked contractions in the pulmonary artery. Under chronic hypoxic condition, [Ca^2＋ ]i was increased. Under normoxic condition, [Ca^2＋ If was （123.634-18.98） nmol/ L, and in hypoxic condition, [Ca^2＋]i wag （281. 754-16.48） nmol/L （P〈0. 01）. Under normoxic condition, [Ca^2＋ ]i showed no significant change and no effect on Clca channels was observed （P〉 0. 05）. Chronic hypoxia increased [Ca^2＋ ]i which opened Clca channels. The NFA and IAA-94 blocked the channels and decreased [Ca^2＋ ]i from （281.75± 16.48） nmot/L to （117.66 ±15.36） nmol/L （P〈0.01）. MTT assay showed that under chronic hypoxic condition NFA and IAA-94 decreased the value of absorbency （A value） from 0. 459±0. 058 to 0. 224±0. 025 （P〈0. 01）. Hypoxia increased [Ca^2＋ ]i which opened Cl~ channels and had a positive-feedback in [Ca^2＋ ]i. This may play an important role in hypoxic pulmonary hypertension. Under chronic hypoxic condition, Clca channel may play a part in the regulation of proliferation of PASMCs.

Inhibitory actions of mibefradil on steroidogenesis in mouse Leydig cells： involvement of Ca^2＋ entry via the T-type Ca^2＋ channel

Intracellular cAMP and Ca^2＋ are involved in the regulation of steroidogenic activity in Leydig cells, which coordinate responses to luteinizing hormone （LH） and human ehorionic gonadotropin （hCG）. However, the identification of Ca^2＋ entry implicated in Leydig cell steroidogenesis is not well defined. The objective of this study was to identify the type of Ca^2＋ channel that affects Leydig cell steroidogenesis. In vitro steroidogenesis in the freshly dissociated Leydig cells of mice was induced by hCG incubation. The effects of mibefradil （a putative T-type Ca^2＋ channel blocker） on steroidogenesis were assessed using reverse transcription （RT）-polymerase chain reaction analysis for the steroidogenic acute regulatory protein （STAR） mRNA expression and testosterone production using radioimmunoassay. In the presence of 1.0 mmol L-1 extracellular Ca^2＋, hCG at 1 to 100 IU noticeably elevated both StAR mRNA level and testosterone secretion （P 〈 0.05）, and the stimulatory effects of hCG were markedly diminished by mibefradil in a dose-dependent manner （P 〈 0.05）. Moreover; the hCG-induced increase in testosterone production was completely removed when external Ca^2＋ was omitted, implying that Ca entry is needed for hCG-induced steroidogenesis. Furthermore, a patch-clamp study revealed the presence of mibefradil-sensitive Ca^24- currents seen at a concentration range that nearly paralleled those inhibiting steroidogenesis. Collectively, Our data provide evidence that hCG-stimulated steroidogenesis is mediated at least in part by Ca^2＋ entry carried out by the T-type Ca^2＋ channel in the Leydig cells of mice.

Functional remodeling of Ca^(2+)-activated Cl^-channel in pacing induced canine failing heart

Objective To determine whether Ca2+ activated Cl- current(Icl(Ca)) contributes to the functional remodeling of the failing heart.Methods Whole cell patch-clamp recording technique was employed to record the Icl(Ca) in cardiac myocytes enzymatically isolatedfrom rapidly pacing induced canine failing hearts at room temperature and compared that of the normal hearts (Nor).Results Thecurrent density of DIDS(200M)sensitive Icl(Ca) induced by intracellular Ca2+ release trigged by L-type Ca2+ current(Ica,L)wassignificantly decreased in heart failare(HE)cells compared to Nor cells.At membrane voltage of 20mV,the Icl(Ca) density was 3.02±0.54 pA/pF in Nor(n=6)vs.1.31±0.25 pA/pF in HF(n=8)cells,(P＜0.01),while the averaged Ica,L density did not show differencebetween two groups.The time constant of current decay of Icl(Ca) was similar in both types of cells.On the other hand,in intra cellularCa2+ clamped mode,where the[Ca2+];was maintained at 100nmol/L,Icl(Ca) density be increased significantly in HF cells when themembrane voltage at+30mV or higher.Conclusions Our results suggest that Icl(Ca) density was decreased in pacing induced failingheart but the channel function be enhanced.Impaired Ca2+ handing in HF cells rather than reduced,Icl(Ca) channel function itself may havecaused this abnormality.The Icl(Ca) density reduction might contribute to the prolongation of action potential in failing heart.The Icl(Ca)channel function up-rugulation is likely to cause cardiac arrhythmia by inducing a delayed after depolarization,when Ca2+ overloadoccurred in diastolic failing heart cells.

Effect of Calmodulin and Voltage-dependent Ca^(2+) Channel on the Proliferation of Heptoma Cells Induced by Epidermal Growth Factor

The effect of thyrosine kinase, calmodulin and voltage-dependent Ca 2+ channel on the proliferation of hepatoma cells induced by EGF was studied. Hepatoma cell line SMMC7721 was cultured in RPMI1640 serum-free medium. DNA synthesis rate of hepatoma cells was measured by 3H-TdR incorporation. 10 -9 mol/L EGF could significantly stimulate the proliferation of hepatoma cells (P<0.05), and this effect might be significantly inhibited by tyrosine kinase inhibitor (P<0.001). Calmodulin inhibitor W-7 had no effect on the basic phase of cultured hepatoma cells (P> 0.05), but it had very significantly inhibitory effect on the proliferation of hepatoma cells induced by EGF (P<0.001). Voltage-dependent Ca 2+ channel inhibitor Varapamil had no inhibition on the proliferation of hepatoma cells induced by EGF (P>0.05). It had no effect on the basic phase of cultured hepatoma cells (P>0.05). It is suggested that tyrosine kinase and Ca 2+-calmodulin-dependent pathway may play a critical role on the proliferation of heptoma cells induced by EGF, and voltage-dependent Ca 2+ channel is independent of the effect of EGF.

2-aminoethoxydiphenyl borate or lanthanum potentiates transient receptor potential-like channels in rat CA1 hippocampal neurons

Expression of transient receptor potential （TRP） channels is widespread with transcripts distributed throughout the brain. All TRP channel subunits are activated following phospholipase C activation and form cation-selective ion channels. Previous studies examining the existence of TRP channels in hippocampal CA1 pyramidal neurons were based on cultured neurons. Therefore, their relevance for living tissue remains unclear. In the present study, patch-clamp recordings were conducted from CA1 pyramidal neurons in hippocampal slices from 7-day-old rats. Whole-cell currents were obtained from CA1 hippocampal neurons with potentiation effects of 2-aminoethoxydiphenyl borate and lanthanum, revealing that recorded experimental currents were characteristic TRP-like channel currents. Identification of rat hippocampal mRNA transcripts of TRPC4, TRPC5, TRPV1, TRPV2, and TRPV3 channels further verified the expression of characteristic TRP-like channels on rat CA1 hippocampal neurons.

Caribbean maitotoxin elevates [Ca^(2+)]i and activates non-selective cation channels in HIT-T15 cells

AIM:To investigate the cytotoxic mechanism of caribbean maitotoxin(MTX-C) in mammalian cells.METHODS:We used whole-cell patch-clamp techniques and fluorescence calcium imaging to determine the cellular toxic mechanisms of MTX-C in insulin secreting HIT-T15 cells,which is a system where the effects of MTX have been observed.HIT-T15 cells stably express L-type calcium current,making it a suitable model for this study.Using the fluorescence calcium indicator Indo-1 AM,we found that there is a profound increase in HIT-T15 intracellular free calcium 3 min after application of 200 nmol/L MTX-C.RESULTS:About 3 min after perfusion of MTX-C,a gradual increase in free calcium concentration was observed.This elevation was sustained throughout the entire recording period.Application of MTX-C did not elicit the L-type calcium current,but large cationiccurrents appeared after applying MTX-C to the extracellular solution.The current-voltage relationship of the cation current is approximately linear within the voltage range from-60 to 50 mV,but flattened at voltages at-80 and-100 mV.These results indicate that MTX-C induces a non-voltage activated,inward current under normal physiological conditions,which by itself or through a secondary mechanism results in a large amount of cationic influx.The biophysical mechanism of MTX-C is different to its isoform,pacific maitotoxin(MTX-P),when the extracellular calcium is removed.CONCLUSION:We conclude that MTX-C causes the opening of non-selective,non-voltage-activated ion channels,which elevates level of intracellular calcium concentration and leads to cellular toxicities.

Effects of isoflurane and ethanol on large conductance Ca^(2+)-activated K^+ channels

Objective: To study the effect of isoflurane and ethanol on large conductance Ca 2+-activated K + channels(BK channels). Methods: The cRNA of mslo1 encoding BK channels was injected into Xenopus oocytes. Oocytes were incubated in ND96 (96 mmol/L NaCl, 2.0 mmol/L KCl, 1.8 mmol/L CaCl 2, 1.0 mmol/L MgCl 2, and 5.0 mmol/L HEPES, pH 7.4) at 4 ℃. Patch clamp recording (outside-out) were performed after 2-3 d. Isoflurane was administrated by the vaporizer driven by air, ethanol was applied by a closed, manual-controlled administration system. Different test potentials from 0 to 10 mV were given to observe changes of currents. Results: 0.7 mmol/L and 1.2 mmol/L of isoflurane could inhibit BK currents obviously at different command potentials, but 50 mmol/L, 100 mmol/L, or 200 mmol/L of ethanol had no any effect on BK currents. Conclusion: Clinical concentration of isoflurane can distinctly inhibit isolating BK currents.

Changes of Ca^2+ activated potassium channels and cellular proliferation in autogenous vein grafts

Objective: To investigate changes of Ca2+ activated potassium channels (KCa) in autogenous vein grafts. Methods: Contraction of venous ring was measured by means of perfusion in vitro. The intimal rabbits proliferation of vascular and proliferation of cultured smooth muscle cells(vascular smooth muscle cells, VSMCs)were observed by the means of computerised image analysis and MTT method respectively. Furthermore, whole cell mode of patch clamp was used to record KCa of VSMCs isolated from autogenous vein grafts. Results: One week after transplantation there were no significant differences of contraction and intimal relative thickness between autogenous vein grafts and control. Contraction and intimal relative thickness of autogenous vein graft were significantly increased 2 weeks after transplantation (P<0.05, n=8 vs control), and they was more enhanced 4 weeks after vein transplantation (P<0.01, n=8 vs control).TEA(blocker of Ca2+ activated potassium channels)increased MTT A490 nm value of VSMCs from femoral vein in a dose dependent manner(P<0.05, n=8). KCa current density was significantly attenuated in VSMCs from autogenous vein grafts (1-4) week after transplantation(P<0.05, n=5).Conclusion: KCa is inhibited in autogenous vein graft, which account for vasospasm and intimal proliferation.

Correlation of large conductance Ca2+ activated K+ channelα andβ subunit expression in uterine smooth muscle with the postpartum hemorrhage induced by uterine inertia

Objective:To study the correlation of large conductance Ca2+ activated K+ channel (BKCa)α andβ subunit expression in uterine smooth muscle with the postpartum hemorrhage induced by uterine inertia.Methods: The puerperae who underwent cesarean section and had postpartum hemorrhage induced by uterine inertia in Panzhihua Women and Children Health Hospital between March 2015 and May 2017 were selected as the hemorrhage group of the study, and the puerperae who underwent cesarean section and were without postpartum hemorrhage in Panzhihua Women and Children Health Hospital during the same period were selected as the control group. Proper amount of uterine muscle tissue was collected during the cesarean section to measure the expression of BKCaα andβ subunits and the levels of contraction-related proteins in uterine muscle as well as the contraction characteristic parameters of the uterine muscle.Results: The mRNA expression and protein expression of BKCaα andβ subunits in uterine muscle tissue of hemorrhage group were significantly higher than those of control group;the contraction amplitude, contraction frequency and contraction activity of uterine muscle tissue as well as the OTR, COX2, CX43 and HSP27 levels in uterine muscle tissue of hemorrhage group were significantly lower than those of control group;the BKCaα andβ subunit expression in uterine muscle tissue of hemorrhage group were negatively correlated with the contraction amplitude, contraction frequency and contraction activity as well as the OTR, COX2, CX43 and HSP27 levels.Conclusion: The high expression of BKCa in uterine smooth muscle can reduce the uterine muscle contractility and decrease the levels of contraction-related proteins, and it is closely related to the occurrence of postpartum hemorrhage induced by uterine inertia.

三七皂甙单体Rb_1对心肌细胞Ca^（2＋）内流作用的研究

应用Ｆｕｒａ－２荧光技术及放射配基结合实验探讨三七皂甙单体Ｒｂ１对心肌细胞胞外Ｃａ２＋内流的作用。０．０４ｍｍｏｌ·Ｌ－１Ｒｂ１可以抑制高钾引起的大鼠心肌细胞胞浆Ｃａ２＋浓度的升高，且呈浓度依赖性；可以完全阻断高钾基础上的异丙肾上腺素的作用。其作用与钙通道拮抗剂维拉帕米类似。Ｒｂ１对大鼠心肌细胞膜上β受体亲和力和受体数均无明显影响。结果提示：Ｒｂ１对心肌细胞电压依赖性钙通道开放引起的胞内钙升高有抑制作用；对β受体相关联的钙通道开放引起的胞浆Ｃａ２＋升高也有抑制作用。而不影响β受体本身。

萘甲异喹对大鼠心肌细胞Ca^(2+)内流的影响

目的研究萘甲异喹（NI）对大鼠心肌细胞外Ca(2+)内流的影响。方法：应用钙离子荧光指示剂Fura－2检测。结果：NI（3，10μmol·L(-1)）和维拉帕米（0．3μmol·L(－1)）对静息状态下心肌细胞内Ca(2+)浓度无影响，但可浓度依赖地抑制高钾（60mmol·L(-1)）和异丙肾上腺素（lμmol·L(－1)）引起的心肌细胞内Ca(2+)浓度的升高，抑制率分别为29％±6％、49％±9％和26％±6％、40％±8％；NI对两种激动剂作用的抑制百分率无明显差异，而维拉帕米对高钾作用的抑制大于对异丙肾上腺素作用的抑制。结论：NI对心肌细胞电压依赖性钙通道以及和β受体有关的钙通道有阻断作用，NI可能是非选择性钙通道阻滞剂。

甜菜碱通过钙通道升高鼠脾淋巴细胞内[Ca^(2+)]i研究

研究甜菜碱对小鼠脾淋巴细胞内钙离子浓度的变化及相关钙通道的研究.应用激光共聚焦显微镜(LSCM)测小鼠脾淋巴细胞内钙浓度的变化,应用不同钙通道阻滞剂研究甜菜碱影响细胞内钙浓度变化途径.对终浓度4 mmol/L甜菜碱作用淋巴细胞不同时间的细胞内钙离子浓度值分析表明:甜菜碱可以使淋巴细胞内Ca2+浓度升高,6 h后效果最明显;对加入不同阻滞剂细胞内钙离子浓度变化分析表明:钙通道及蛋白阻滞剂硝苯地平、地尔硫卓、咪贝地尔、金雀异黄素对甜菜碱升高淋巴细胞内钙离子浓度没有影响;维拉帕米、新霉素、肝素、普鲁卡因能阻断甜菜碱对淋巴细胞内钙离子浓度的升高作用.由此可知:细胞内钙离子浓度升高主要通过以下途径:在G蛋白介导下通过影响L-型电压门控钙通道的α1亚单位而引起外钙内流;通过影响胞内钙库的IP3R钙通道和RyR钙通道而引起内钙外排.其共同引起胞质钙离子浓度增加.

Cl^-通道阻断剂对5-HT和CPA引起的兔脑椎基底动脉平滑肌细胞Ca^(2+)内流的影响

目的 在培养的兔脑椎基底动脉平滑肌细胞上观察5 HT和CPA诱导的Ca2 + 内流的特性 ,电压依赖性Ca2 + 通道 (VDC)抑制药尼莫地平 ,非电压依赖性Ca2 + 通道抑制药SK&F963 65及Cl-通道阻断剂DIDS、NPPB对两种激动剂引起 [Ca2 + ]i 反应的影响 ,以探讨脑血管平滑肌细胞中 5 HT引起Ca2 + 内流的特性、Cl-通道与Ca2 + 内流的关系。方法 采用生物荧光双波长影像分析系统瞬即测定单细胞胞质[Ca2 + ]i 技术。结果 ① 5 HT和CPA均能诱导平滑肌细胞[Ca2 + ]i 呈双相升高 ,并且 5 HT诱导的Ca2 + 释放是环匹阿尼酸 (CPA)敏感Ca2 + 池的一部分 ;②尼莫地平对 5 HT和CPA触发的Ca2 + 内流无明显影响 ,而SK&F963 65可阻止二者触发的Ca2 + 内流 ;③Cl-通道阻断剂DIDS、NPPB呈浓度依赖性抑制Ca2 + 内流 ,在SK&F963 65最大限度抑制Ca2 + 内流后 ,DIDS、NPPB可进一步抑制Ca2 + 内流 ;而Ca2 +内流被DIDS、NPPB分别最大抑制后 ,SK&F963 65也可进一步抑制Ca2 + 内流。结论 5 HT引起的Ca2 + 内流是经SK&F963 65敏感的非VDC ,其中包含Ca2 + 释放引起的Ca2 + 内流 (CRAC)成分与非CRAC成分 ,并且这两部分Ca2 +内流均与DIDS。

心衰大鼠心肌SR Ca^(2+)泵活性和Ca^(2+)释放通道密度的变化及培哚普利干预的影响

目的 探讨ACEI干预慢性心衰对心肌肌浆网 (SR)Ca2 + 泵活性和Ca2 + 释放通道 (RyR2 )密度的影响及意义。方法 通过结扎大鼠左冠脉建立慢性心衰模型 ,以培哚普利进行干预 ,对照观察血流动力学、左室心肌SRCa2 + 泵活性、[3 H]-ryanodine与RyR2 最大结合量 (Bmax)、Kd 值。结果 与对照组 (C组 )相比 ,心衰组 (F组 )LVEDP显著升高 (P <0 0 1) ,+dp/dtmax、-dp/dtmax显著降低 (P <0 0 1) ,培哚普利组 (P组 )LVEDP显著低于F组 (P <0 0 1) ,+dp/dtmax、-dp/dtmax显著高于F组 (P <0 0 1)。F组心肌SRCa2 + 泵活性、[3 H]-ryanodine与RyR2 最大结合量Bmax显著低于C组 (P <0 0 1) ,也显著低于P组 (P <0 0 1) ,三组Kd 值无显著差异 (P >0 0 5 )。心肌SRCa2 + 泵活性与 +dp/dtmax、-dp/dtmax显著正相关 (r=0 5 16 1、0 6 172 ,P <0 0 1)。结论 培哚普利长期干预慢性心衰 ,能够改善心肌SRCa2 + 泵活性 ,增加RyR2 密度 ,可能与其改善心肌舒缩功能及心肌保护作用有关。

巯亚硝基卡托普利对环匹阿尼酸引起的平滑肌细胞胞浆游离Ca^(2+)浓度升高作用的影响

目的 探讨巯亚硝基卡托普利 (S nitrosocaptopril,CapNO)对Ca2 + 池操纵性Ca2 + 内流信号转导过程的影响。方法 以Fura 2荧光探针测定胞浆游离Ca2 + 浓度([Ca2 + ]i)。结果 ①CapNO(2 0～ 12 0 μmol·L-1)呈浓度依赖性抑制环匹阿尼酸 (cyclopiazonicacid ,CPA)引起的[Ca2 + ]i 升高 ,80 μmol·L-1CapNO为最大效应浓度。相同浓度的captopril对CPA升高 [Ca2 + ]i 无明显抑制作用。②在 80 μmol·L-1CapNO抑制CPA引起 [Ca2 + ]i 升高作用的基础上 (31%± 11% ) ;随后加入 1μmol·L-1硝苯地平不能降低 [Ca2 + ]i,再加入 2 0 μmol·L-1SK&F96 36 5 (最大效应浓度 )可进一步降低 [Ca2 + ]i(5 4%± 18% ) ,其中SK&F96 36 5净抑制率为 2 4%± 10 % ,与SK&F96 36 5单独作用抑制率(5 4%± 11% )比较差异有显著性。③不同顺序给予最大效应浓度CapNO (80 μmol·L-1)和tyrphostinAG490 (2 μmol·L-1)对CPA引起 [Ca2 + ]i 升高存在交叉抑制作用。结论 CapNO可通过阻断电压依赖性Ca2 + 通道和Ca2 + 池操纵性Ca2 + 通道抑制CPA引起的 [Ca2 + ]i 升高 ,CapNO对CPA引起 [Ca2 + ]i 升高的阻断作用存在酪氨酸激酶 (Janus2亚型 )

Ca^(2+)对角质形成细胞增殖与分化调控的作用研究

目的:探讨胞外Ca2+对人角质形成细胞(HKC)的增殖与分化的调控作用,为组织工程皮肤的研制提供依据。方法:HKC体外培养,应用形态学、免疫细胞化学、MTT等方法检测胞外Ca2+对HKC增殖与分化的影响,并利用钙通道阻滞剂SK&F 96365来研究其作用的可能途径。结果:Ca2+为0.5mmol/L时,HKC呈单层生长,免疫细胞化学显示HKC呈低分化状态,当Ca2+为1mmol/L与1.5mmol/L时,细胞在3天后出现复层生长,免疫细胞化学显示细胞K19角蛋白表达减少,Ca2+为2.0mmol/L时表现出一定的细胞毒性作用,SK&F 96365可逆转Ca2+的促增殖与分化作用。结论:胞外Ca2+在一定范围内具有促HKC分化与增殖的作用,并且该作用可以被SK&F 96365所阻滞。

库容性Ca^(2+)内流参与ACh诱导的大鼠远端结肠平滑肌收缩

应用生物换能技术和Ca2+通道特异性阻断剂观察并记录大鼠离体远端结肠平滑肌收缩张力的变化,分析库容性 Ca2+内流(capacitative Ca2+ entry,CCE)是否与ACh诱导的离体远端结肠平滑肌收缩反应有关。结果表明,以无钙的Krebs 液灌流或应用EGTA螯合细胞外Ca2+后,高K+及ACh引起的远端结肠平滑肌收缩几乎完全消失。电压操纵性Ca2+通道阻断剂veiapamil也能减弱高K+及ACh引起的远端结肠平滑肌收缩,其减弱的程度分别为74％和41％。在无钙的Krebs液中, 5 μmol／L ACh可引起离体肠管瞬时性收缩,这是由肌质网(sarcoplasmic reticulum,SR)释放钙所致;然后加入10 μmol／L阿托品(atropine),并在此基础上恢复细胞外Ca2+(2．5 mmol／L),结肠平滑肌则出现持续性收缩,待收缩反应达峰值时,加入5μmol／L verapamil,收缩无明显变化,且该收缩反应对钙库操纵性通道(store-operated Ca2+ channel,SOCC)阻断剂La3+ 敏感,20,50和100 μmol／L的La3+使上述收缩张力分别降低15％,23％和36％,且呈浓度依赖性,但对Cd2+不敏感。研究结果提示,细胞外Ca2+内流对高K+及ACh介导的离体远端结肠平滑肌持续性收缩是必需的,由ACh诱导的远端结肠平滑肌收缩至少包括SR释放钙引起的短暂性收缩及受体操纵性Ca2+通道(receptor-operated Ca2+ channel,ROCC)、电压操纵性Ca2+通道(voltage-operated Ca2+ channel,VOCC)和CCE介导的胞外Ca2+内流等途径。这将从通道水平进一步分析消化管平滑肌收缩的机制和特征,亦将为预防和控制因胃肠动力紊乱所致的消化管疾病寻求有针对性的药物干预和治疗提供理论依据。

高压氧对脑缺血及再灌注时海马游离Ca^（2＋）及钙通道的作用

应用新型钙离子荧光指示剂Ｆｕｒａ－２／ＡＭ测定海马突触体内游离Ｃａ￣（２＋）浓度，观察在脑缺血时及不同压力高压氧治疗后的变化规律，并应用［￣３Ｈ］ＰＮ２００－１１０作为放射性配基，用放射配体结合法测定海马组织Ｌ－型钙通道生物学特性和缺血及高压氧治疗后的变化。结果表明：脑缺血及再灌注后海马脑区突触体内游离Ｃａ￣（２＋）浓度显著增加，其Ｌ－型钙通道的Ｂｍａｘ和Ｋｄ值均显著上升，但经吸入高压氧后，可降低胞浆内游离Ｃａ￣（２＋）浓度，其中以２５３．２５ｋＰａ高压氧作用明显，并可降低钙通道的Ｂｍａｘ与Ｋｄ值。说明高压氧部分地通过减少细胞内游离Ｃａ￣（２＋）而起作用，Ｌ－型钙通道参与了高压氧降低脑缺血后胞浆内游离Ｃａ￣（２＋）浓度的作用，高压氧可使其开放的通道数量减少。

西洋参茎叶皂苷对大鼠心肌细胞Ca^(2+)内流的影响

目的 :研究西洋参茎叶皂苷 (PQS)对大鼠心肌细胞Ca2 + 内流的影响。方法 :应用钙离子荧光指示剂Fura 2 /AM检测。结果 :PQS(1.5mg/ml)和维拉帕米 (0 .5 μmol/L)对静息状态下心肌细胞内Ca2 + 浓度均无明显影响 ,但PQS使心肌细胞内Ca2 +浓度有下降趋势 ;两药可明显抑制高钾 (5 0mmol/L)引起的心肌细胞内Ca2 + 浓度的升高。结论 :PQS对心肌细胞电压依赖性钙通道有阻断作用。