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Aim To investigate the role of mechano- sensitive ion channel Piezol in regulating electrical re-modeling of atrial myocytes induced by hypertension and to further explore the potential mechanisms.Methods Spontaneously hypertensive rats ( SHR ) aged 30 - 32 weeks treated with or without valsartan (30 mg • kg 1 • d 1 ) were used.Wistar rats were used as control.Western blot was used to detect the protein expression of Piezol , Src and Cavl.2 in atrial appendages of rats and in atrial myocytes ( HL-1 cells) exposed to different levels of high hydrostatic pressure (20 and 40 mmHg) , Piezol inhibitor (GsmTx4) and agonist ( Yodal ) in vitro.Whole-cell patch clamp technique was employed to detect L-tvpe calcium current (ICa, ) and action potential duration ( APD) of atrial myocytes.Results Compared with Wistar rats in control group, the protein expressions of Piezol and Src significantly increased and the expression of Cavl.2 decreased in SHR group (P < 0.05 ), while the a- bove changes could he reversed in SHR treated with valsartan( P < 0.05 ) .Meanwhile, higher hydrostatic pressure (40 mniHg) could increase the expressions of Piezol and Src in HL-1 cells( P <0.05) and decrease the protein expression of Cavl.2 (P <0.05 ) , accompanied by a shortened APD and a decreased ICa,.GsmTx4 could significantly reverse the above changes.In addition, Piezol agonist Yodal could simulate electrical remodeling and related signal molecule changes in atrial myocytes induced by the high hydrostatic pressure.Conclusions Mechanosensitive ion channel Piezol participates in electrical remodeling induced by hypertension via activating Src kinase signaling pathway and then leading to the decrease of ICa ,.
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Aim To explore the role of cotranscriptional activator p300 in regulating the electrical remodeling of atrial myocytes in aging mouse, which resulted in atrial fibrillation. Methods The left atrial appendage tissues of 5 , 13 and 18monthold C57BL/6 mice were collected respectively. Western blot was used to detect the protein expression levels of p300, L type calcium channel (Cavl. 2) and aging related protein p53/p21. Acute enzymatic hydrolysis was used to isolate single atrial myocytes, and the wholecell patchclamp technique was used to detect the Ltype calcium current (I
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[ ABSTRACT] AIM:To establish a perforated whole-cell patch-clamp technique withβ-escin to record L-type cal-cium current (ICa,L) in osteoblasts.METHODS:ROS 17/2.8 is a rat osteoblast-like osteosarcoma cell line.β-escin was applied to the pipette solution to permeabilize the cell membrane and the perforated patch recording mode was obtained. RESULTS:β-escin at concentration of 50μmol/L easily permeabilized the cell membrane and obtained a perforated patch recording mode in 2~7 min.This technique prevented ICa,L rundown and preserved cytoplasmic signaling pathways.CON-CLUSION:β-escin may be used as an alternative ionophore for perforated patch-clamp studies in osteoblasts and results in minimal rundown that could facilitate recordings of ICa,L in osteoblasts.
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Objective: To observe the effect of cilostazol on the ion channel of right ventricular cells in experimental rats, and to explore the ion channel mechanism of ciolstazol for preventing the ventricular arrhythmia in Brugada syndrome. Methods: Our research was composed of 2 groups: ①Perfusion group, the cells were treated in 4 sub-groups by cilostazole at 1, 2, 5, 50μmol/L respectively, and there were 9, 5, 3, 7 cells were recorded at each sub-group to observe the differences of current density Ito at before and after treatment. ②Oral group, which included 4 sub-groups:Control 1 with 7 rats, Experiment 1 with 5 rats, and Control 2 with 8 rats, Experiment 2 with 6 rats respectively. The differences of current density Ito and ICa,L were studied between each Control and Experiment sub-groups. Results: In Perfusion group,①with cilostazole 1, 2, 5, 50μmol/L treatment, the current density Ito decreased in all sub-groups, when the self-command voltage at+60mV, the Ito was signiifcantly different in each sub-group at before and after treatment, all P0.05. In Oral group,①When the self-command voltage from-50mV reached the maximum of+60mV, the Ito was similar between Control 1 and Experiment 1 sub-groups, P>0.05.②When the self-command voltage at+10mV, the current density of ICa,L was slightly higher in Control 2 sub-group than that in Experiment 2 sub-group, P>0.05. Conclusion: Direct perfusion of cilostazole in right ventricular cells may inhibit Ito in experimental rats, such effect was similar with cilostazole treatment at (1-50)μmol/L. Cilostazole might prevent the ventricular arrhythmia in Brugada syndrome in experimental rats.
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Objective To investigate the effect of the calmodulin kinase Ⅱ Inhibitor KN-93 on L-typecalcium current(ICa,L)and intracellular calcium concentration([Ca2+]i)in hypertrophic cardiac myocytes.Methods Forty-eight female New Zealand white rabbits were randomized(random number)into four groups(12 animals in each group):the sham operation group(sham group),the left ventricular hypertrophy group(LVH group),the myocardial hypertrophy + KN-93 group(KN-93 group),and the myocardial hypertrophy + KN-92 group(KN-92 group).Myocardial hypertrophy in the rabbits was established by coarctation of the abdominal aorta.In the sham group,the abdominal aorta was dissociated without coarctation.Eight weeks after coarctation,single ventricular myocytes were isolated by enzymaticdissociation,and ICa,L was recorded using perforated-patch recording(PPR)techniques.[Ca2+]i was measured using single-cell calcium imaging with the fluorescence calcium indicator dye fura-2/AM.Results Cardiac hypertrophy was successfully established after 8 weeks of coarctation of the abdominal aorta.The peak ICa,L in the LVH group and the sham group was(1.38 ± 0.3)nA and(0.87 ± 0.1)nA at 0 mV,respectively(P ＜0.01,n =12).There was no significant difference in Ica,L density between the LVH group and the sham group[(6.7 ±1.0)pA/pF vs.(6.3±0.7)pA/pF; P≥0.05,n=12].The addition of either KN-92(0.5 μmol/L)or KN-93(0.5 μmol/L)to the perfusing solution caused a modest steady-state inhibition of peak ICaL(9.4％ ±2.8％,KN-92; 10.5％ ±3％,KN-93)(P≥0.05,n =12)at 0 mV.However,at a higher concentration(1 μmol/L),KN-93 more potently inhibited peak ICa,L(40％±4.9％)compared to KN-92(13.4％ ± 3.7％ ; P ＜ 0.01,n =12).Resting[Ca2+]i levels in fura-2-loaded myocytes isolated from the sham,LVH,KN-92,and KN-93 groups were(98 ± 12.3)nmol/L,(154 ± 26.2)nmol/L,(147 ± 29.6)nmol/L,and(108 ± 21.2)nmol/L,respectively.Conclusions The CaMK Ⅱ specific inhibitor,KN-93,can effectively block ICa,L and reduce intracellular calcium overload in hypertrophic cardiac myocytes.This action may account for the antiarrhythmic effect of KN-93 in hypertrophic ventricular myocardium.
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Objective To assess the anti-arrhythmic activity and cardioprotective effects of Wenxin Granula, a traditional Chinese formula (consisting of Salviae Miltiorrhizae Radix, Polygonati Rhizoma, Notoginseng Radix et Rhizoma, Nardostachyos Radix et Rhizoma, Angelicae Sinensis Radix, and Succinum), on heart in ischemic-induced myocardial infarction (MI) rats and compare with those of Amiodarone which have been demonstrated in clinic. Methods Rats were randomly divided into Sham-operated (control), Ml + Amiodarone [5 mg/(kg·d)] (MI), and MI + Wenxin Granula [10 mg/(kg·d)] groups and left anterior descending coronary artery was occluded in each group. After left anterior descending for 12 h, standard lead Ⅱ of administration electrocardiogram was recorded in order to analyze the occurrence of arrhythmia. After one month, the size of the infarct area of heart was evaluated by TTC staining method and haemodynamic function was assessed to detect the heart function. Laser scanning confocal microscope and the technique of patch clamp were used to detect the intracellular Ca2+ ([Ca2+]j) and L-type calcium current (ICa-L), respectively. Results Both Wenxin Granula [10 mg/(kg·d)] and Amiodarone [5 mg/(kg·d)] could markedly decrease the incidence of arrhythmia in heart of rats which were subjected to ischemic injury. After one month, Wenxin Granula could significantly decrease mortality to 22.22% and reduce the infarct area (P < 0.05), but Amiodarone did not. The mechanism may involve that Wenxin Granula attenuated [Ca2+]j decreasing in MI rats. Additionally, Wenxin Granula could obviously ameliorate the impaired heart function of MI rats by decreasing the elevated left ventricular end-diastolic pressure and increasing the attenuated maximum change velocity of left ventricular pressure in the isovolumic contraction or relaxation period. On the other hand, electrophysiological experiment results revealed that Wenxin Granula administration one month later also increased the reduced ICa-L density in rat ventricular myocytes in MI rats. The results of LSCM showed that Wenxin Granula could recover the amplitude of [Ca2+]j decreased by heart failure during long term. Conclusion Wenxin Granula could not only inhibit the incidence of arrhythmia but also decrease the mortality, which was accompanied by recovering the amplitude of [Ca2+]j. This protective effect of Wenxin Granula may partially be mediated through changing ICa-L.as well as increasing [Ca2+]j.
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Aim To observe the effect of Ginkgo biloba extract 50(GBE50)on L-type calcium current and cytosolic[Ca~(2+)]_i in ischemic guinea pig ventricular myocytes.Methods Single ventricular myocytes were isolated by enzymatic dissociation. I Ca-L was recorded by whole-cell patch clamp technique in voltage clamp mode.[Ca~(2+)]_i was detected by laser confocal micros-copy and represented by relative fluorescent intensity (FI).Results During ischemia, the peak Ca~(2+) current was reduced, and the I-U curve of I Ca-L was shifted upward.50 mg·L~(-1) GBE50 reversed the change induced by ischemia(n =6, P >0.05).After perfusing ischemic solution for 12 min, intracellular calcium concentration was increased(n =10, P <0.01).After perfusion with ischemic solution containing 50 mg·L~(-1) GBE50, the increase of intracellular calcium concentration was markedly inhibited(n =10, P >0.05).Conclusion GBE50 can reverse the decrease of I Ca-L and partially inhibit calcium overloading during ischemia.
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AIM: To evaluate the effects of simulated acute ischemia and reperfusion on L-type calcium current (ICa,L) in ventricular myocytes from diabetic and non-diabetic rabbits.METHODS: Using whole-cell patch clamp techniques, ICa,L was measured in left ventricular myocytes isolated from 6-week alloxan-induced diabetic rabbits and age-matched control ones at baseline, 5 min of simulated ischemia, and 5 min of reperfusion.RESULTS: There were no significant differences on baseline maximum ICa,L densities between diabetic and control ventricular myocytes. In control cells (n=11), maximal ICa,L densities of baseline, ischemia and reperfusion were (-8.36±1.63)pA/pF, (-5.90±1.75)pA/pF and (-4.22±1.02)pA/pF, respectively. The ICa,L of ischemia was less than that of baseline (P<0.01), while the ICa,L of reperfusion was less than those of baseline (P<0.01) and ischemia (P<0.05). In diabetic cells (n=9),the ICa,L of baseline, ischemia and reperfusion were (-7.55±1.62)pA/pF, (-6.05±1.58)pA/pF and (-5.12±1.13)pA/pF, respectively. Only ICa,L of reperfusion was less than that of baseline (P<0.01), while ICa,L of ischemia was not significantly different from that of baseline (P>0.05) or reperfusion (P>0.05).CONCLUSION: ICa,L in diabetic ventricular myocytes represents blunted response to acute ischemic injury, being decreased more slowly than that in control cells. Post-ischemic reperfusion is still a potent inhibitor against ICa,L in both diabetic and non-diabetic cells. This study may be indicative of the mechanism about ischemia-reperfusion injury to diabetic myocardium and the therapy for diabetic patients with ischemic heart disease.
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Objective To determine the effects of valsartan, a specific angiotensin Ⅱ type 1 receptor blockade, on arrhythmia in rabbits after myocardial infarction and to discuss the mechanism. Method Twentyfour rabbits were randomly (random number) divided into sham operated (SO) group ( n = 8), myocardial infarction (MI) group ( n = 8) and valsartan (VAL) group ( n = 8). The rabbits of SO group were operated upon with median stemotomy without left ventricular coronary artery hgature. The rabbits of MI group and VAL group had median stemotomy with left ventricular coronary artery ligature. After MI, the rabbits of VAL group were fed with border zone of infracted left ventricular wall and the L-type calcium current was recorded by whole-cell patch clamp technique. Results Ventricular tachycardia or fibrillation (VT/VF) episodes were markedly decreased in VAL group than that in MI group [(3.2 ± 0. 6) vs. ( 11.7 ± 1.8)] after 12 weeks. The density of Ica-L current was higher in MI group than that in SO group and VAL group [( - 9.12 ± 0.73) pA/pF vs. ( - 6.29 ± 0.65) pA/pF and ( - 6.75 ± 0.64) pA/pF], ( P ＜ 0.05), however, there were no significant differences in Ica-L current between So group and VAL group ( P ＞ 0.05). Conclusions Valsartan reduces the VT/VF episodes in rabbits after MI. The effects of valsartan may be attributed to the inhibited electrical remodeling after MI.
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To elucidate the mechanism of cyclic nucleotides, such as adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5' -cyclic monophosphate (cGMP), in the regulation of human gastric motility, we examined the effects of forskolin (FSK), isoproterenol (ISO) and sodium nitroprusside (SNP) on the spontaneous, high K+ and acetylcholine (ACh)-induced contractions of corporal circular smooth muscle in human stomach. Gastric circular smooth muscle showed regular spontaneous contraction, and FSK, ISO and SNP inhibited its phasic contraction and basal tone in a concentration-dependent manner. High K+ (50 mM) produced sustained tonic contraction, and ACh (10 micrometer) produced initial transient contraction followed by later sustained tonic contraction with superimposed phasic contractions. FSK, ISO and SNP inhibited high K+-induced tonic contraction and also ACh-induced phasic and tonic contraction in a reversible manner. Nifedipine (1 micrometer), inhibitor of voltage-dependent L-type calcium current (VDCC(L)), almost abolished ACh-induced phasic contractions. These findings suggest that FSK, ISO and SNP, which are known cyclic nucleotide stimulators, inhibit smooth muscle contraction in human stomach partly via inhibition of VDCCL.
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Humans , Acetylcholine , Adenosine , Calcium , Contracts , Colforsin , Guanosine , Isoproterenol , Muscle, Smooth , Nifedipine , Nitroprusside , Nucleotides, Cyclic , Relaxation , StomachABSTRACT
It was previously showed that aqueous leaf extract (AqEx) of Averrhoa carambola depresses the guinea pig atrial inotropism. Therefore, experiments were carried out on guineapig left atrium and on pituitary GH3 cells in order to evaluate the effect of AqEx on the cellular calcium infl ux. The atrium was mounted in an organ chamber (5 mL, Tyrode, 27 ± 0.1 °C, 95% O2, 5 % CO2), stretched to 10 mN, and paced at 2 Hz (0.5 ms, 400 V) and GH3 cells were submitted to a whole cell voltage clamp confi guration. In the atrium, the AqEx (1500 μg/mL) shifted to the right the concentration-effect curve of the positive inotropic effect produced by (±) BAY K 8644, an L-type calcium channel agonist. The AqEx increased EC50 (concentration required to promote 50% of the maximum effect) of the inotropic effect of BAY K 8644 from 7.8 ± 0.38 to 115.1 ± 0.44 nM (N = 3; p < 0.05). In GH3 cells assayed with 500 μg/mL of AqEx, the L-type calcium inward current declined 30 % (from 282 to 190 pA). Nevertheless, the extract did not change the voltage correspondent to the peak current. These data suggest that, at least in part, the negative inotropic effect of AqEx on the guinea pig atrium is due to a reduction of the L-type calcium current.
Em estudo prévio mostrou-se que o extrato aquoso das folhas de Averrhoacarambola (ExAq) reduziu o inotropismo atrial da cobaia. Por isso, este trabalho avaliou se o ExAq interfere com o infl uxo de cálcio através da membrana celular. A investigação foi conduzidaem átrio esquerdo de cobaia, montado em cuba (5 mL, Tyrode, 27 ± 0,1 °C, 95 % O2, 5 % CO2), estirado para uma tensão de repouso de 10 mN e submetido a uma estimulação de 2 Hz (0,5 ms, 400 V). O efeito do ExAq sobre a entrada de cálcio nas células foi avaliado em átrio de cobaia e em células GH3, estas submetidas a patch clamp na confi guração whole cell. No átrio, o ExAq (1500 μg /mL) deslocou para direita a curva concentração-efeito do (±) BAY K 8644 (agonista dos canais de cálcio tipo-L), aumentando a CE50 (concentração capaz de produzir 50 % do efeito máximo) de 7,8 ± 0,38 para 115,1 ± 0,44 nM (N = 3, p < 0,05). Em células GH3, este extrato (500 μg /mL) reduziu de 282 para 190 pA (30 %) a corrente de cálcio, sem contudo alterar a voltagem de pico da curva desta corrente. Estes resultados mostram que, pelo menos em parte, o efeito inotrópico negativo do ExAq em átrio de cobaia se deve a uma diminuição do infl uxo de cálcio pelos canais tipo-L.
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Objective To study the intervention effect of tanshinone on electrophysiological abnormality of hypertrophic cardicoyte in order to illuminate the underlying mechanism of tanshinone in preventing the arrhythmia induced by myocardial hypertrophy. Method Twenty-week-rid SD rats (200～250 g) were divided into 4 groups (8 in each group) randomly. Of 4 groups, rats of three groups were operated on by a procedure of 'one kidney one clamp' to make renal artery constriction. The rest group served as sham operation group (control group). When the blood pressure increased,rats of operation groups were divided into tanshinone group, captopril group and hyper-trophic group. The effects of tanshinoe and captopril were observed and compared on the action potential duration (APD),L-type calcium current (ICa, L) and transient outward potassium current (Ito) density in cellular membrane of hypertrophic myocardium by using patch clamp and intra-cellular calcium survey technique. Results The blood pressure in operation groups was obviously higher than that in sham-operation group (P<0.01), but there was no difference between operation groups (P>0.05). The ratio of ventricle weight to body weight (VW/BW) was much higher in hypertrophic group than in control group (P<0.01), and it significantly decreased after interven-tion with tanshinone or captopril (P<0.01). Compared with hypertrophic group, tanshinone markedly shortened the prolongation of action potential duration (P<0.01), decreased membrane capacity and peak amplitude of ICa,L(P<0.01), but had no effect on the density of ICa,L. Tanshinone also significantly increased Ito current density and peak amplitude, which were completely different from hypertrophic group (P<0.05). There were similar results foundin captopril intervention. Conclusions Tanshinone could reduce calcium influx and resume the activity of ho ion channels, and thus shorten the first phase and the plateau phase of repolarization and decrease the prolongation of APD in hypertrophic cadiocyte. So tanshinone can prevent the onset of arrhythmia attributed to the myocardial hypertrophy.
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Objective To study the biological effect of ?3 adrenoceptor-activated electrophysiological activities in cardiac myocytes. Methods Changes of transient outward potassium ( Ito) and L-type calcium current ( ICa-L) in primary cultured guinea pig cardiacmyocytes were detected with the standard whole-cell patch clamp technique about 5 -10 min before and after administration of ?3 adrenoceptor agonist,4--2-hydroxy-( 3-chlorophenyl) ethyl-aminopropylphenoxyacetate ( BRL-37344; BRL). Results BRL could significantly increased the Ito in guinea pig cardiac myocytes with the I-V curve up-moved. When the membrane potential reached to + 80 mV,the density current increased from 6. 11 ? 1. 03 pA/pF to 8. 46 ? 2. 07 pA/pF ( n = 6,P =0. 013 064). BRL ( 10 -6mol/L) could significantly increase the ICa-Lin guinea pig cardiac myocytes,which was ( 2. 30 ?0. 75) -fold higher than in control group( n =5,P =0. 0063). When the membrane potential increased to + 10 mV ,the current,increased from 89. 25 ? 17. 83 pA to 205. 00 ? 72. 24 pA ( n = 5,P = 0. 006 3). Conclusion BRL-37344 can increase the transient Itoand ICa-L,thus further regulating the cardiac activities.
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Objective To determine the changes of L-type calcium currents(I Ca-L ) of rabbit ischemic myocytes in peri-infarcted zone.Methods Rabbit AMI models were made by ligation of branches of left coronary artery. After 1 week and 2 months, single pericardial myocytes were isolated enzymatically from ischemic zone adjacent to infarcted area and the normal control cells from similar regions in normal rabbit hearts. I Ca-L were recorded by using patch clamp techniques in the whole cell configuration. Results Peak of I Ca-L density of ischemic cells from the peri-infarcted zone was significantly reduced in AMI onc week later ( 3 52 0 93 pA/pF, n=6) compared to control cells ( 5 58 1 53pA/pF,n=10), P0 05 The steady-state inactivation curves were shifted to the hyperpolarizing direction in ischemic cells,the half-maximal voltage dependence of inactivation(V 1/2 ) in ischemic cells was 25 9 7 0 mV in AMI 1W , 21 3 5 6mV in AMI 2M and 13 1 4 2mV in the control cells(compared with control group,P
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BACKGROUND: We have previously reported that not only cGMP but also 8-Br-cGMP or 8-pCPT-cGMP, specific and potent stimulators of cGMP-dependent protein kinase (cGMP-PK), increased basal L-type calcium current (ICa) in rabbit ventricular myocytes. Our findings in rabbit ventricular myocytes were entirely different from the earlier findings in different species, suggesting that the activation of cGMP-PK is involved in the facilitation of ICa by cGMP. However, there is no direct evidence that cGMP-PK can stimulate ICa in rabbit ventricular myocytes. In this report, we focused on the direct effect of cGMP-PK an ICa in rabbit ventricular myocytes. METHODS AND RESULTS: We isolated single ventricular myocytes of rabbit hearts by using enzymatic dissociation. Regulation of ICa by cGMP-PK was investigated in rabbit ventricular myocytes using whole-cell voltage clamp method. ICa was elicited by a depolarizing pulse to +10 mV from a holding potential of -40 mV. Extracellular 8-(4-Chlorophenylthio)-guanosine-3',5'-cyclic monophosphate (8-pCPT-cGMP), potent stimulator of cGMP-dependent protein kinase (cGMP-PK), increased basal ICa. cGMP-PK also increased basal ICa. The stimulation of basal ICa by cGMP-PK required both 8-Br-cGMP in low concentration and intracellular ATP to be present. The stimulation of basal ICa by cGMP-PK was blocked by heat inactivation of the cGMP-PK and by bath application of 8-(4-chlorophenylthio)-guanosine-3',5'-cyclic monophosphate, Rp-isomer (Rp-pCPT-cGMP), a phosphodiesterase-resistant cGMP-PK inhibitor. When ICa was increased by internal application of cGMP-PK, IBMX resulted in an additional stimulation of ICa. In the presence of cGMP-PK, already increased ICa was potentiated by bath application of isoprenaline or forskolin or intracellular application of cAMP. CONCLUSIONS: We present evidence that cGMP-PK stimulated basal ICa by a direct phosphorylation of L-type calcium channel or associated regulatory protein in rabbit ventricular myocytes.
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1-Methyl-3-isobutylxanthine , Adenosine Triphosphate , Baths , Calcium Channels, L-Type , Calcium , Colforsin , Heart , Hot Temperature , Isoproterenol , Muscle Cells , Phosphorylation , Protein KinasesABSTRACT
Objective To study the effects of mimic ischemic preconditioning (IP) on i and I-LCa of sinoatrial node cells and explore the protective effects of IP. Methods Cells were randomized to three groups: control, ischemia/reperfusion (I/R), IP. After labeled with fura4, fluorescence intensity of i was studied with laser confocal microscopy and I-LCa was recorded by whole-cell patch clamp technology. Results IP significantly reduced the fluorescence intensity of i and enhanced the peak of I-LCa as compared with I/R, shifted the I-V curve to more negative value. Conclusion IP can reduce the overload of i caused by I/R and increase I-LCa weakened by I/R.
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Aim To investigate the effect of hypercholesterolemia on L-type Ca2+(ICa-L) current and intracellular calcium concentration ([Ca2+]i) in single ventricular myocytes of hypercholesterolemic rats.Methods 12 male wistar rats were randomly divided into two dietary groups:a group fed a normal diet(n=6)and a group fed high-cholesterol diet(n=6) for 4 weeks,respectively. The level of serum lipid was examined.Zymolytic method was used to isolate single ventricular myocytes from hypercholesterolemic and normal rats,which were loaded with Ca2+-sensitive fluorescent indicator Fluo-3/AM.[Ca2+]i represented by fluorescent intensity(FI)was measured by laser scanning confocal microscope.Whole cell patch clamp technique was used to record ICa-L.Results There was no significant influence exhibited on TG level.However, the serum total cholesterol(TC)level of hypercholesterolemic rats was much higher than that of model control group; at the test potential of 0 mV, ICa-L decreased from(-8.56?1.29)pA/pF(Control)to(-5.24?0.90) pA/pF(HC)(n=6 in each group,P
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Aim To investigate the effects of emodin on the contraction of gallbladder smooth muscle(GBSM)and the L-type calcium current in GBSM cells.Methods Gallbladder muscle strips were obtained from adult guinea pigs and the resting tension was recorded.Gallbladder smooth muscle cells were isolated by enzymatic digestion,and calcium current was recorded by the whole-cell patch clamp method.Results Emodin-induced contraction of GBSM was significantly attenuated by pretreatment with nifedipine.Emodin increased the L-type calcium current in a dose-dependent manner.When 10 ?mol?L-1 emodin was applied to GBSM cells,the amplitude of L-type calcium current at +10 mV was enhanced by(45.2?2.26)%.In the presence of PKC inhibitor,staurosporine,emodin did not significantly affect the calcium current.Conclusion Emodin enhances L-type calcium current via PKC-dependent pathway and promotes gallbladder contraction.
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AIM To investigate the effects of levo phenoprolamine hydrochloride [ levo 1 (2,6 dimethylphenoxy) 2 (3,4 dimethoxyphenyl ethylamino) propane hydrochloride] [ l DDPH([?]D 25 1 08)]on experimental arrhythmias. on experimental arrhythmias. METHODS Intravenous administration of ouabain, aconitine or CaCl 2 induced arrhythmias in rats or guinea pigs; Microelectrode recording was used to record action potential; Whole cell patch clamp technique was used to record L type calcium current ( I Ca,L ). RESULTS ① l DDPH 50 mg?kg -1 inhibited the ventricular arrhythmias induced by intravenous injection of ouabain in guinea pigs or aconitine and CaCl 2 in rats. ② l DDPH 30 ?mol?L -1 shortened 50% action potential duration (APD 50 ) and prolonged effective refractory period (ERP) ( n =6, P