Effect of garlicin on sodium channel current in rat ventricular myocytes

AIM: To observe the effect of garlicin on sodium channel(I_Na) in isolated ventricular myocytes of rats. METHODS: The ventricular myocytes of rats were obtained by enzymatic dissociation and treated with different concentrations of garlicin. The change of I_Na was recorded by the technique of whole-cell patch clamp recording.RESULTS: Garlicin decreased the I_Na of isolated ventricular myocytes in a dose- and voltage-dependent manner. The current density was elevated to peak under the condition that the membrane voltage was -40 mV before treated with garlicin. The current density was decreased by 48% from peak after treated with 500 μmol/L garlicin . No significant change of the active curve with the use of garlicin was observed. The median inactive voltages of the inactive curves before and after garlicin treatment were (-88.61±9.60) mV and (-103.03±8.90) mV (P<0.01), respectively, and the slopes were -7.85±0.88 and -7.55±2.75 (P>0.05), respectively, indicating that garlicin made a shift to the negative direction. CONCLUSION: Garlicin treatment induced the current density-voltage curve of I_Na to shift up and significantly decreased the current density. The inactive curve of sodium channel moved to the left, while the current density was not decreased after treated with garlicin. Garlicin blocks sodium channel in its inactive state in a dose- and voltage-dependent manner.     

Effect of breviscapin on INa channel current in isolated rat ventricular myocytes

AIM: To investigate the effects of breviscapine on INa channel in isolated rat ventricular myocytes. METHODS: Single cell of rat ventricular myocyte was isolated by enzymatic dissociation. The whole-cell patch-clamp recording technique was used to observe the change of INa channel current influenced by breviscapine. RESULTS: Breviscapine decreased the INa channel current in a dose-dependent and voltage-dependent manner in rat ventricular myocytes. The current-voltage curve was significantly decreased. Breviscapin at concentrations of 1, 3, 30, 100 mg/L respectively decreased INa current density, which were (7.98±0.60)%, (37.73±2.31)%, (65.58%±2.90)% and (88.09±5.60)%, respectively. INa was inhibited in a voltage-dependent manner, showing a significant attenuating effect at test potentials from -30 mV to 0. The INa inactivation curve was shifted to left and the activation curve was shifted to right. Breviscapine step down the recovery curve significantly. CONCLUSION: Breviscapine concentration-dependently decreased INa channel current in rat ventricular myocytes.     

Effects of endothelin and endothelin receptor antagonist on funny current and its gene expression in neonatal rat ventricular myocytes

AIM: To analyze the effect of endothelin-1 (ET-1) and ET-1 receptor antagonist on funny current (If) and its gene (hyperpolarization-activated cation channel, HCN) expression in neonatal rat ventricular myocytes. METHODS: Fresh ventricular myocytes were isolated from 1-3 d rats. The expression of If gene was measured by real-time quantitative polymerase chain reaction (real-time PCR). If was recorded and studied through whole-cell patch clamp. The cardiomyocytes were stimulated by ET-1 (0, 1, 10, 100 nmol/L) for 3 hours, or ET-1 (100 nmol/L) for 0, 0.5, 1, 3, 6 hours or ET-1 plus ETA- or ETB-receptor antagonist (BE-18257B or IRL-1038), respectively. RESULTS: HCN1, HCN2, HCN3, HCN4 represented (0.23±0.01)%, (83.58±0.04)%, (0.79±0.01)%, (15.44±0.01)% of total HCN mRNA, respectively. If was recorded. When cells were stimulated by ET-1 (10, 100 nmol/L), HCN2 was significantly increased by 0.1, 2 times and HCN4 was increased by 0.1, 0.5 times. When cells were stimulated for 0.5, 1, 3 and 6 hours, HCN2 was significantly increased by 0.3, 1, 5, 5.1 times and HCN4 was increased by 0.1, 0.6, 2, 2.1 times. The treatment of the combination of ET-1 plus BE-18257B significantly decreased HCN2 and HCN4 level. However, HCN1 and HCN3 had no statistically significant change. If would be increased by ET -1 and this effect was reverted by BE-18257B. IRL-1038 had no effects on If and HCN. CONCLUSION: (1) HCN2 and HCN4 represent a large amount of total HCN mRNA in neonatal rat ventricular myocytes. (2) If and the expression of HCN2 and HCN4 are increased by ET-1, this effect is reverted by BE-18257B.     

Interleukin-2 altered the frequency -dependent relationship of intracellular calcium in rat ventricular myocytes

AIM:We examined the effect of interleukin-2 (IL-2) on calcium handling of rat cardiomyocytes. METHODS:The effects of steady state and transient changes in stimulus frequency on the intracellular calcium transient were investigated in the isolated ventricular myocytes with spectrofluorometry technique. RESULTS: Under the steady state (0.2 Hz), IL-2 at 2×10⁵U/L decreased the peak [Ca²⁺] i and amplitude of the [Ca²⁺]i transient, increased the diastolic calcium level, and prolonged the decay of the calcium transient. At 1.25 mmol/L of extracellular [Ca²⁺], when increasing the stimulus frequency from 0.2 to 1.0 Hz, diastolic calcium level and peak [Ca²⁺] i as well as the amplitude of the transient were increased. The positive frequency relationship was blunted in the IL-2-treated myocytes and this was not normalized by increasing extracellular [Ca²⁺] to 2.5 mmol/L. The caffeine induced Ca²⁺ release was increased with increase in stimulus frequency. IL-2 inhibited the frequency relationship of caffeine induced Ca²⁺ release. The restitution was not different between control and IL-2 groups at the 1.25 mmol/L of extracellular [Ca²⁺], which was slowed in IL-2-treated myocytes when the extracellular [Ca²⁺] was increased to 2.5 mmol/L. CONCLUSIONS:It is concluded that the blunted frequency response of IL-2-treated myocytes was resulted from the decrease in SR Ca²⁺ release, which was related to depression of SR function. Despite the evidence of depressed SR Ca²⁺ uptake, the restitution of calcium transient at 1.25 mmol/L of extracellular remains unchanged, which maybe due to the increase in the Na⁺/Ca²⁺ exchanger activity.     

Effect of interleukin-2 on intracellular calcium levels in rat ventricular myocytes during anoxia and reoxygenation

AIM: To investigate the effect of interleukin-2(IL-2) on the intracellular calcium in electrically stimulated adult rat ventricular myocytes during anoxia and reoxygenation. METHODS: The isolated cardiac ventricular myocytes were exposed to 5 min anoxia followed by 10 min reoxygenation. Chemical anoxia was introduced by Krebs-Henseleit(K-H) solution containing 10^-3 mol/L sodium dithionite. The spectrofluorometric method was used to verify intracellular calcium transient with fura-2/AM as calcium fluorescence probe. RESULTS: It was shown that during anoxia, the amplitude of Ca²⁺ transient was decreased, diastolic [Ca²⁺]_i, time to peak and time to relaxation of Ca²⁺ transient were increased. All the parameters were got back but did not returned to the pre-anoxia level during reoxygenation. IL-2 at 2×10⁵ U/L administrated during anoxia aggravated the effect of rexoxygenation on [Ca²⁺]_i transient. Pretreatment with a specific κ opioid antagonist, nor-BNI(10^-8 mol/L), abolished the effect induced by IL-2 during anoxia on the [Ca²⁺]_i transients, whereas specific δ opioid antagonist, naltrindole(10^-6 mol/L), did not cancel the effect. CONCLUSION: It is concluded that administration of IL-2 during anoxia aggravated the effect of reoxygenation on the [Ca²⁺]_i transients of isolated ventricular myocytes, which was mediated by cardiac κ opioid receptor pathway.     

Nuclear calcium oscillation in cultured neonatal rat myocytes

AIM: To determine whether nuclear Ca²⁺ is independently regulated from the cytosolic Ca²⁺ and nuclear Ca²⁺ oscillation induced by many modulating factors in cultured rat neonatal myocytes and its mechanism. METHODS: Rat neonatal cardiac myocytes were cultured, and fluo-4/AM was loaded as calcium probe. The changes of cytosolic and nuclear Ca²⁺ were observed by confocal laser microscopy. RESULTS: Calcium fluorescent intensity oscillated slightly in myocardiocytes and the average intensity was much higher in the nucleus than that in the cytosole. Ca²⁺ oscillation in nucleus and cytosole induced by norepinephrine, isoproperenol, ATP were completely blocked by Ca²⁺-ATPase antagonist thapsigargin (10^-6 mol/L),L-type Ca²⁺ channel blocker verapermil (500 μmol/L) and KCl (20 mmol/L). Ca²⁺-ATPase antagonist thapsigargin completely blocked the propagation of Ca²⁺ waves and simutaneouly induced a temporary Ca²⁺ increase followed by a magnificient drop and loss of response to norepinephrine. CONCLUSIONS: The results suggested that generation and maintenance of calcium oscillation both in cytosole and nucleus depended on extracellular Ca²⁺ influx, membrane potential, Ca²⁺ release and uptake of cytosolic and nuclear calcium stores. The difference between cytosolic calcium and nuclear calcium indicated that calcium regulating system relatively independent of cytosole may exist in nucleus.     

Hypoxia facilitates rapid pacing-induced calcium transient alternations in ventricular myocytes

AIM:To explore the effect of hypoxia on rapid pacing-induced calcium transient alternations in ventricular myocytes.METHODS:Ventricular myocytes were isolated from the heart of adult SD rats and cultured in serum-free hypoxic fluid to set up an in vitro model of hypoxia-induced cardiac injury. The calcium transient and its alternations were investigated under confocal laser scanning microscope. The mitochondrial function was also examined by WST-8 kit. RESULTS:Under normoxic condition, the ventricular myocytes were claviform. Low frequency of pacing, ranging from 60 to 240 min^-1, induced calcium transient, but not calcium transient alternations, which was elicited by the pacing over a threshold frequency of(288 ±27)min^-1. Exposure of the ventricular myocytes to hypoxia did not obviously affect the morphology of the cells, but reduced the threshold frequency of pacing to(227±26) min^-1(P<0.05). Additionally, exposure of the cells to hypoxia repressed the activity of mitochondrial dehydrogenase from(100.2±8.7)%(control group) to(57.6±7.5)%, which was partially blocked by L-type Ca²⁺ channel inhibitor. CONCLUSION:Hypoxia facilitates calcium transient alternations induced by rapid pacing, and the calcium transient alternations are involved in the hypoxia-injured mitochondria function.     

Effect of oxymatrine on sodium channel in isolated ventricular myocytes in guinea pig

AIM: To observe the effect of oxymatrine on sodium channel in isolated cardiomyocytes of guinea pig. METHODS: Single ventricular myocytes of guinea pigs were obtained by enzymatic dissociation. The whole-cell patch clamp recording technique was used to record the change of sodium current by different dosage of oxymatrine from 1 to 1 000 μmol·L-1. RESULTS: Oxymatrine decreased sodium current in a dose-dependent manner. Oxymatrine (100 μmol·L-1) decreased the current density by 40% (P<0.01). The current-voltage curve was moved up and active potential, peak potential and reverse potential had no change. The inactivation curve was moved to more negative potential and the recovery curve was delayed. The activation curve had no significant change. CONCLUSION: Oxymatrine decreases the sodium channel current in a dose-dependent and voltage-dependent manner.     

Effects of alcohol on L-type calcium channel of atrial myocytes in guinea pig

AIM: To observe the effect of acute alcohol intervention on atrial myocytic L-type calcium ion channels (ICa.L) in guinea pig by whole-cell patch clamp technique. METHODS: Guinea pig atrial myocytes were obtained by enzymolysis. Whole-cell patch clamp was used to gain the I-V curve, availability curve and activity curve of ICa.L with or without different concentrations of alcohol. RESULTS: The I-V curves of ICa.L were changed by alcohol in a concentration-dependent manner. Inhibition occurred when the alcohol concentration was less than 45 mmol/L, while enhancement was observed with a concentration more than 50 mmol/L. A sudden alternation between the two effects was observed with the alternation between the two concentrations. Alcohol concentration higher to 80 mmol/L did not change the I-V curve. Alcohol did not change the activity curve or availability curve of ICa.L except the former at concentration of 80 mmol/L. CONCLUSION: Alcohol affects ICa.L in a non-voltage-dependent way and a concentration-dependent manner where different concentrations of alcohol make inverse effects. That may help to elucidate the relationship between atrial fibrillation and atrial flutter.     

An approach to calcium signal transmission between L-type calcium channel and sarcoplasmic reticulum of atrial myocytes during atrial fibrillation

AIM: To inquire into the Ca2+ signal transmission from L-type calcium channel to the sarcoplasma reticulum in atrial fibrillation. METHODS: Ten adult cross-bred dogs were used in the experiment. Five dogs underwent continuous rapid atrial pacing (500±20 beats/min) for twenty-four weeks to create persistent atrial fibrillation. Another group of size-matched dogs (n=5) without pacemaker implantation was used as a control group. Canine atrial myocytes were isolated by enzymatic dissociation. The Ca2+ cytosolic transient in atrial myocytes was analyzed by confocal imaging after loading myocytes with the acetoxymethyl ester of fluo-3 (Fluo-3/AM). Ca2+ signal transmission from L-type Ca2+ channels in the plasma membrane to the sarcoplasma reticular IP3R and RyR in atrial myocytes during atria fibrillation were measured. RESULTS: (1) Ca2+ signal transmission from L-type calcium channel to IP3R in the sarcoplasma reticulum:intracellular Ca2+concentration was slightly increased in two groups after blocking T-type calcium channel and RyR, but showed no statistic significance (P＞0.05) between them. (2) Ca2+ signal transmission from L-type calcium channel to RyR in the sarcoplasma reticulum: intracellular Ca2+concentration was risen (1.5576±0.1989) in control groups after blocking T-type calcium channel and IP3R, and no significance was observed (P＞0.05) compared with that in atrial fibrillation group (1.5372±0.2952). CONCLUSIONS: Ca2+ signal transmission possibly exists from L-type calcium channel to RyR and IP3R in the sarcoplasma reticulum, but it does not play an important role in intracellular Ca2+-overload and abnormal Ca2+ signal transmission during atrial fibrillation.     

Effects of resveratrol on the L-type calcium current by protein kinase G pathway in isolated guinea pig ventricular myocytes

AIM: To investigate the effects of resveratrol on the L-type calcium current in isolated guinea pig ventricular myocytes. METHODS: The whole cell patch clamp method was used. RESULTS: （1）Resveratrol (1, 50, 100 μmol/L) reduced the I_Ca-L by 18.31%±3.15%, 56.20%±2.50% and 84.51%±4.01% in a concentration-dependent manner (n=5, P<0.05). But it has no change on I-V shape of I_Ca-L. (2) 8Br-cGMP (100 μmol/L), an activator of protein kinase G(PKG), deduced the density of I_Ca-L by 10.50%±1.11%. Applying resveratrol and 8Br-cGMP simultaneously decreased the I_Ca-L significantly by 87.58%±3.49％ (n=6, P<0.05). (3) 5 μmol/L H8, a PKG inhibitor, inhibited the decrease in I_Ca-L caused by resveratrol. CONCLUSION: Resveratrol inhibits I_Ca-L in guinea pig ventricular myocytes, and this inhibitory effect involves the PKG pathway.     

Blunted response of L-type calcium current to simulated ischemia and reperfusion in ventricular myocytes from diabetic rabbits

AIM: To evaluate the effects of simulated acute ischemia and reperfusion on L-type calcium current (I_{Ca, L}) in ventricular myocytes from diabetic and non-diabetic rabbits.METHODS: Using whole-cell patch clamp techniques, I_{Ca, 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 I_{Ca, L} densities between diabetic and control ventricular myocytes. In control cells (n=11), maximal I_{Ca, 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 I_{Ca, L} of ischemia was less than that of baseline (P<0.01), while the I_{Ca, L} of reperfusion was less than those of baseline (P<0.01) and ischemia (P<0.05). In diabetic cells (n=9), the I_{Ca, 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 I_{Ca, L} of reperfusion was less than that of baseline (P<0.01), while I_{Ca, L} of ischemia was not significantly different from that of baseline (P>0.05) or reperfusion (P>0.05).CONCLUSION: I_{Ca, 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 I_{Ca, 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.     

Electrical heterogeneity of transient outward current in thyroxine induced ventricular myocytes of cardiomyopathy rat

AIM: To study the electrical heterogeneity of transient outward potassium current (Ito) in left and right ventricular myocytes of cardiomyopathy rat. METHODS: The rats were peritoneally injected with L-thyroxine 0.5 mg/kg for 10 d to establish the model of ventricular hypertrophy. The right and left ventricular parts of the heart were separated and the ventricular myocytes were prepared by step digestion using enzyme solution. Ito was recorded by using whole cell patch clamp technique. The change of the electrical heterogeneity was determined. RESULTS: The electrical heterogeneity of Ito existed in the normal myocytes of left and right ventricles. In the myocytes of left and right ventricles isolated from the cardiomyopathy rats, the electrical heterogeneity was enhanced obviously and showed statistical difference. At +40 mV depolarizing test potential, the current density of Ito in the myocytes of right ventricle was increased from (9.23±0.84) pA/pF to (11.19±1.73) pA/pF, while the current density of Ito in the myocytes of left ventricle was decreased from (6.99±1.14) pA/pF to (4.95 ±1.84) pA/pF and the dispersion was increased. The V1/2 of right ventricle steady inactivation was increased significantly ［from (-68.85±1.37) mV to (-49.86±0.69) mV］. The time constant τ of de-inactivation changed significantly ［τleft=(79.16±7.04) ms,τright=(53.19±3.72) ms］. CONCLUSION: Enhanced electrical heterogeneity of Ito in the left and right ventricular myocytes of cardiomyopathy rat may represent one of the important ionic mechanisms for some arrhythmia caused by myocardial hypertrophy.     

Role of calcium activated potassium channel in cardioprotection induced by anoxic postconditioning in isolated rat heart

AIM:To investigate whether calcium activated potassium channel (KCa) and mitochondrial permeability transition pore (mPTP) contribute to cardioprotective effect elicited by anoxic postconditioning.METHODS:The isolated perfused hearts of male Sprague-Dawley rats were subjected to 30 min global anoxic followed by 120 min reoxygenation. Formazan content of myocardium was measured at 490 nm spectrophotometrically,and the level of lactate dehydrogenase (LDH) in the coronary effluent was detected. The absorbance of isolated heart mitochondria at 520 nm was determined. RESULTS:Anoxic postconditioning increased formazan content,reduced LDH release,improved the hemodynamic parameters of the left ventricular developed pressure,maximal rise/fall rate of left ventricular pressure,left ventricular end-diastolic pressure and rate pressure product and attenuated the decrease of coronary flow during reperfusion. Pretreatment with paxilline (1 μmol/L) inhibited the effect of anoxic postconditioning. The opening of mPTP was suppressed in the mitochondria isolated from A/R hearts treated with anoxic postconditioning.CONCLUSION:The findings indicate that in the isolated rat heart,anoxic postconditioning protects myocardium against anoxic/reoxygenation injury via inhibiting KCa and the mPTP opening.     

Interleukin-2 pretreatment improves the contractility of isolated rat ventricular myocytes during hypoxia and reoxygenation

AIM: To investigate the effect and possible mechanisms of interleukin-2 (IL-2) on the cell contractility in cardiomyocytes during hypoxia and reoxygenation.METHODS: Glucose-free Krebs-Henseleit (K-H) solution, gassed with 95% N2 and 5% CO2 for hypoxia, were used. The cell contractility were determined after 20 min of hypoxia and 30 min of reoxygenation by the video tracking system. The parameters of cell contractility included peak velocity of cell shortening (+dL/dtmax), peak velocity of cell relengthening (-dL/dtmax), contraction amplitude (dL) and end-diastolic cell length.RESULTS: It was shown that during hypoxia, the cell contraction was depressed. All the parameters were unable to return to the pre-hypoxia level during reoxygenation. Pretreatment with IL-2 at 2×103 U/L attenuated the inhibitory effect of hypoxia/reoxygenation on contractility in single ventricular myocytes. The effect of IL-2 was reduced in the presence of 10-8 mol/L nor-binaltorphimine (nor-BNI), a selective κ-opioid receptor antagonist. On blockade of protein kinase C with 3×10-6 mol/L chelerythrine, the effect of IL-2 was significantly attenuated. The effect of IL-2 was also blocked by 10-4 mol/L 5-hydroxydecanoate (5-HD), a mitochondrial ATP-sensitive potassium (KATP) channel blocker. CONCLUSIONS: The results of the present study provide evidence that pretreatment with IL-2 at 2×103 U/L attenuates the effect of hypoxia/reoxygenation on cell contraction in the isolated ventricular myocytes. The κ-opioid receptor mediates the effect of IL-2, in which activation of PKC and opening of mitochondrial ATP-sensitive potassium (mito KATP) channel are involved.     

Effects of calmodulin antagonist and slow calcium channel antagonist on reperfusion injury of isolated rat hearts in calcium paradox

AIM: To observe the protective effect of calmodulin antagonist trifluoperazine(TFP) and slow calcium channel antagonist verapamil (VP) upon calcium overload injury. METHODS: The calcium content of the myocardium, lactate dehydrogenase (LDH) release, protein loss and coronary flow were measured after the isolated rat hearts were perfused by TFP and VP. RESULTS: TFP could significantly reduce the tissue calcium , LDH release and protein loss of the myocardium ( P <0.01) while VP had no such effects.The above indexes were further reduced when TFP and VP were used simutaneously( P <0.01).CONCLUSION:TFP can effectively alleviate the severity of the myocardium injury during calcium paradox while VP has no such effects.The simultanous use of VP and TFP is more effective in preventing tissue damage of the heart than the use of TFP alone.The massive influx of Ca²⁺ in calcium paradox is mainly a calmodulin related process.     

Effect of hypoxia on persistent sodium current in ventricular myocytes from 3-week infarcted rat heart

AIM: To investigate the effect of hypoxia on persistent sodium current (INap) in single ventricular myocyte isolated from acute myocardial infarction (AMI) heart of rats and to study the mechanisms of cardiac arrhythmias that occur after AMI. METHODS: AMI model was induced by ligating the left anterior descending coronary artery in rats. The whole-cell patch clamp technique was used to record the current in epicardial myocytes in infarcted region from rats at 3 week after AMI. RESULTS: In normoxic conditions, the current density of INap in cardiomyocytes of fake operation (FO) and AMI hearts was 0.144±0.022 pA/pF (n=9), 0.121±0.013 pA/pF (n=9，P<0.01)， respectively, which was blocked by tetrodotoxin (TTX). The amplitude of INap was gradually increased with the prolongation of hypoxia time, but the increase in extent of INap in FO cells was significant bigger than that in AMI cells. The INap was blocked by 1 mmol/L glutathione. CONCLUSIONS: After AMI, the amplitude of INaP in infarcted and noninfarcted myocardium showed differences both in normoxic and hypoxic conditions, which increased dispersion of repolarization. This may be one of the reasons of reentrant ventricular arrhythmias that occur after AMI.     

Knockdown of IK1 potassium channel inhibits expression and function of ClC-3 chloride channel

AIM: To investigate whether the ClC-3 chloride channel is an acting target of the IK1 potassium channel, and to study the action of IK1 potassium channel on the functional activities and expression of ClC-3 chloride channels. METHODS: IK1 gene was silenced by IK1 siRNA in poorly-differentiated nasopharyngeal carcinoma cells (CNE-2Z). Real-time PCR and Western blot were used to detect the expression of ClC-3 at mRNA and protein levels. The distribution of ClC-3 protein in the cells was observed under confocal immunofluorescence microscope. The chloride current was recorded by the patch-clamp technique. RESULTS: IK1 siRNA was successfully transfected into the CNE-2Z cells and knocked down the expression of IK1 potassium. The mRNA expression of ClC-3 was increased by the IK1 siRNA. IK1 siRNA inhibited the expression of ClC-3 protein. A chloride current was activated by hypotonic challenges, and the hypotonicity-induced current was reduced in the cells which successfully transfected with IK1 siRNA. CONCLUSION: The knockdown of IK1 potassium channels inhibits the expression and function of ClC-3 chloride channel.     

Effects of fluvastatin on the left ventricular function,MHC gene expression and collagen remodeling after myocardial infarction

AIM: To observe the effects of fluvastatin (FV) on the left ventricular (LV) function, MHC mRNA and collagen remodeling of non-infarcted area after acute myocardial infarction (AMI). METHODS: Six hours after ligating left coronary artery, survivors of AMI female SD rats were randomly assigned to: ①AMI control; ②FV; ③sham-operated groups. After 8 weeks of therapy, the LV function, hemodynamics, expression of non-infarcted myocardial MHC mRNA, collagen volume fraction (CVF) and the ratio of type Ⅰ/Ⅲ collagen of non-infarcted area were assessed. RESULTS: Compared with sham-operated group, E wave, E wave deceleration, E/A ratio, LV end diastolic pressure (LVEDP), β MHC mRNA, CVF and the ratio of type Ⅰ/Ⅲ collagen were all significantly increased in AMI group, while fractional shortening (FS), ejection fraction (EF), mean arterial pressure (MAP) and α MHC mRNA were all significantly decreased. In comparison with AMI group, E wave, E wave deceleration, E/A, LVEDP, β MHC mRNA, CVF and the ratio of type Ⅰ/Ⅲ collagen were all significantly decreased, while FS, EF, MAP and α MHC mRNA were all significantly increased in FV group. CONCLUSION: FV improves the LV function after AMI and has beneficial effects on reversing LV myocardial pathologic switching of MHC isoform and collagen remodeling.     

Change of calcium sensing receptor expression and apoptotic pathways in myocardial infarction rat induced by isoprel

AIM:To observe the change of calcium sensing receptor (CaSR) expression and apoptotic pathways in myocardial infarction rat induced by isoprel.METHODS: The myocardial infarction rat models were prepared by subcutaneous injection of isoprel (ISO 200 mg·kg-1·d-1 for 2 d). Wistar rats were divided into three groups randomly: ① Control group; ② ISO/1d group; ③ ISO /2d group. The expressions of CaSR, 〖STBX〗bcl-2, bax〖STBZ〗 and caspase-3 mRNA and protein were analyzed by RT-PCR and Western blotting, respectively. Apoptotic cells were measured by TUNEL staining assay. The morphological and ultrastructural changes were observed under optical microscope and electronic microscope. The activity of LDH, CK, SOD and the content of MDA were assayed with ultraviolet spectrophotometer. The level of troponin(cTnT) was observed by chemical immunofluoresence.RESULTS: Compared with control group, the activity of LDH and CK, the content of MDA and cTnT, the apoptosis index and the expression of CaSR, Bax and caspase-3 were reached the highest level, but the SOD activity and Bcl-2 expression were decreased. The myocardial ultrastructural injury was aggravated in the ISO/1d group. The change of above parameters in ISO/2d group was between control and ISO/1d group.CONCLUSION:The increased expression of CaSR is involved in rat myocardial infarction induced by isoprel, which is related with oxidative stress and apoptosis.