Inhibitory effect of zacopride on ouabain-induced arrhythmias in adult rats

AIM: To investigate the effect of zacopride, an inward rectifier potassium channel agonist, on ouabain-induced arrhythmias in adult rats, and to explore the underlying electrophysiological mechanism.METHODS: Using ouabain to establish in vitro and in vivo arrhythmic rat models, the effects of zacopride on ouabain-induced arrhythmias were observed. The technique of whole-cell patch clamp was used to observe the effects of zacopride on inward rectifier potassium current (I_K1), resting membrane potential (RMP) and delayed afterdepolarizations (DADs) in single rat ventricular myocyte. RESULTS: Zacopride at 1 μmol/L significantly reduced total number of premature ventricular beats, and the duration and incidence of ventricular tachycardia and ventricular fibrillation induced by ouabain in rat hearts in vitro (P<0.05). In anesthetized rats, zacopride at 15 μg/kg significantly reduced total number of premature ventricular beats, and the duration and incidence of ventricular tachycardia and ventricular fibrillation induced by ouabain (P<0.05). I_K1 was significantly inhibited by ouabain (P<0.05), which was partially and even completely reversed by zacopride at 0.1~10 μmol/L. RMP value was significantly reduced by ouabain (P<0.05), and then increased to different levels after treatment with zacopride (0.1~10 μmol/L). Zacopride at 1 μmol/L showed its maximal effect and RMP was restored to normal level. Moreover, zacopride at 1 μmol/L markedly suppressed ouabain-induced DADs in single rat ventricular myocyte. The incidence of DADs decreased from 91.67% to 12.50% after zacopride was applied (P<0.05), and this effect was abolished by 1 μmol/L BaCl₂. CONCLUSION: Inward rectifier potassium channel agonist zacopride significantly inhibits ouabain-induced ventricular arrhythmias in adult rats. The mechanism is related to increased RMP level and inhibition of DADs by activation of I_K1 channel.     

Postconditioning of zacopride depresses ischemia/reperfusion-induced arrhythmias in rats

ATM: To investigate the effects of postconditioning of zacopride, a specific agonist of inwardly rectifying potassium channel (K_ir), on ischemia/reperfusion-induced arrhythmias and the involved electrophysiological mechanisms. METHODS: Langendorff-perfused SD rat hearts or anesthetized rats were subjected to coronary artery occlusion for 15 min followed by 15 min of reperfusion to induce ischemia/reperfusion arrhythmias. Zacopride was applied 3 min before reperfusion. Various arrhythmias were monitored and compared in different groups. The single rat ventricular myocyte was isolated by collagenase digestion. The effects of zacopride on hypoxia/reoxygenation-induced delayed afterdepolarizations (DADs) and ATP-sensitive potassium channel (K_ATP) were observed by the technique of whole-cell patch clamping. RESULTS: Post-conditioning of 0.1~10 μmol/L zacopride significantly prevented the hearts from reperfusion arrhythmias. During reperfusion, 0.1 μmol/L zacopride showed the maximum effect, with decreasing the number of premature ventricular beats (PVB), reducing the incidences of ventricular tachycardia (VT) and ventricular fibrillation (VF), and shorte-ning the duration of VT and VF (P<0.01). The postconditioning effects were partly reversed by 1 μmol/L BaCl₂(P<0.01), suggesting that the antiarrhythmic effect of zacopride was mediated by K_ir. In the in vivo study, 1.5~5 μg/kg zacopride had positive effects on reperfusion-induced VT and VF and negative effect on PVB. At the dose of 1.5 μg/kg, zacopride showed the most potent antiarrhythmic effect, which compared favourably with that of a classical antiarrhythmic agent, lidocaine. Furthermore, zacopride significantly inhibited hypoxia/reoxygenation-induced DADs (P<0.01). Zacopride had no effect on K_ATP.CONCLUSION: The inhibitory effect of zacopride on ischemia/reperfusion-induced arrhythmias is mediated by the activation of K_ir. Augmentation of K_ir cuvrent, thus diminishing the DADs, might be the critical mechanisms underlying postconditioning of zacopride.     

Effect of platelet activating factor on the action potential and potassium currents in guinea-pig ventricular myocytes

AIM: To investigate the effects of platelet activating factor (PAF) on the action potential and potassium currents in guinea-pig ventricular myocytes. METHODS: By using whole-cell patch clamp technique, the effects of PAF on APD₉₀, I_K1 and I_K were investigated in enzymatically dispersed single guinea-pig ventricular myocytes. RESULTS: With 5 mmol/L ATP in the pipette electrode, 1 μmol/L PAF increased APD₉₀ from (225.8±23.3) ms to (352.8±29.8) ms (n=5, P<0.05), decreased I_K1 and I_K tail currents from (-6.1±1.3) nA to (-5.6±1.1) nA (n=5, P<0.05) at -120 mV and from (173.5±16.7) pA to (152.1±11.5) pA (P<0.05, n=4) at +30 mV, respectively. In contract, without ATP in the pipette electrode, 1 μmol/L PAF shortened APD₉₀ from (153.0±24.6) ms to (88.2±19.4) ms (n=5, P<0.01). Incubation of myocytes with 1 μmol/L glibenclamide, a blocker of I_KATP restored prolongation of APD induced by PAF. CONCLUSION: In guinea-pig ventricular myocytes, with 5 mmol/L ATP in the pipette, PAF prolonged APD partly due to the inhibition of I_K and I_K1, while with 0 mmol/L ATP in the pipette, PAF induced an activation of I_KATP, hence a decrease in APD was observed. Therefore, PAF might amplify the heterogeneity between ischemia and normal cardiac myocytes during ischemic reperfusion, which might play a vital role in the pathogenesis of the arrhythmias induced by ischemia/reperfusion.     

Electrophysiological effects of amiodarone on pacemaker cells in guinea-pig left ventricular outflow tract under conditions of hypoxia,acidosis and treatment with epinephrine

AIM: To study the electrophysiological effects of amiodarone on the pacemaker cells in guinea-pig left ventricular outflow tract under the conditions of hypoxia, acidosis and treatment with epinephrine.METHODS: The action potentials of the pacemaker cells in guinea-pig left ventricular outflow tract were recorded by conventional intracellular microelectrode technique. The effects of amiodarone on the spontaneous slow response potentials were investigated under the conditions of hypoxia, acidosis and treatment with epinephrine.RESULTS: (1) Amiodarone at concentration of 0.1 μmol/L markedly decreased the rate of pacemaker firing (RPF) and maximal diastolic potential (MDP), lengthened 80% of the duration of action potential (APD80). Amiodarone at concentration of 1 μmol/L significantly decreased the velocity of diastolic depolarization (VDD) and RPF, the maximal rate of depolarization (Vmax), MDP and amplitude of action potential (APA), lengthened 50% of the duration of action potential (APD50) and APD80. Amiodarone at concentration of 10 μmol/L led to a significant decrease in VDD and RPF, Vmax, MDP and APA, a notable lengthening in APD50 and APD80 was also observed. (2) Under the condition of hypoxia and perfusion with deprived glucose content for 15 min, VDD, RPF, MDP, Vmax and APA decreased significantly, APD50 was shortened notably. Under the condition of hypoxia, amiodarone at concentration of 1 μmol/L significantly decreased VDD, RPF and Vmax, increased MDP, lengthened APD50 and APD80 as compared to the cells treated with hypoxia only. (3) Perfusion with pH 6.8 solution for 10 min, VDD and RPF significantly decreased, Vmax and APA notably reduced, APD80 was markedly shortened. Under the condition of acidosis for 10 min, amiodarone significantly decreased VDD, RPF, MDP and APA, lengthened APD50 and APD80 as compared to the cells under the condition of acidosis only. (4) Perfusion of epinephrine at concentration of 10 μmol/L for 10 min resulted in a significant increase in VDD, RPF, Vmax, MDP and APA, a notable shorting in APD50 and APD80 was also observed. Compared to 10 μmol/L epinephrine group, 1 μmol/L amiodarone+10 μmol/L epinephrine significantly reduced VDD, RPF, Vmax, MDP and APA, lengthened APD50 and APD80.CONCLUSION: Amiodarone markedly decreases the autorhythmicity of the pacemaker cells in guinea-pig left ventricular outflow tract. This electrophysiological effects were significantly influenced by hypoxia, acidosis and epinephrine.     

Receptor and signaling mechanisms involved in zacopride-induced potentiation of IK1

AIM: To investigate the receptor and signaling mechanisms involved in the potentiation of inward rectifier K⁺ current (I_K1) induced by zacopride, a potent 5-HT₃ receptor antagonist and 5-HT₄ receptor agonist. METHODS: The whole-cell patch clamp technique was used to record I_K1. 5-HT₄-receptor antagonist RS23597-190, 5-HT₃-receptor agonist m-chlorophenylbiguanide (m-CPBG), PKA inhibitor KT5720, PKC inhibitor GF109203X and PKG inhibitor KT5823 were applied respectively to determine the regulatory mechanism of I_K1. RESULTS: In the presence of RS23597-190 at concentration of 10 μmol/L which inhibited I_K1, zacopride at concentration of 1 μmol/L still increased I_K1 with the mean increment of 32.5% in inward current (at -100 mV, P<0.05). The I_K1 increment induced by zacopride was not inhibited by m-CPBG at concentration of 10 μmol/L (P>0.05). Furthermore, PKA inhibitor KT5720 at concentration of 5 μmol/L reversed the effect of zacopride (P<0.05), while PKC inhibitor GF109203X and PKG inhibitor KT5823 both at concentration of 5 μmol/L didn't influence the effect (P>0.05). CONCLUSION: Zacopride potentiates I_K1 via a PKA-mediated signaling pathway, which is independent on 5-HT₄ and 5-HT₃ receptors.     

Effects of stretch on transient outward potassium and inward rectifier potassium current in cultured neonatal rat atrial myocytes

AIM：To investigate the effects of mechanical stretch on transient outward potassium current (Ito), inward rectifier potassium current (IK1) and action potential duration(APD) of cultured neonatal rat atrial myocytes. METHODS：Neonatal rat atrial myocytes were isolated and cultured on silicone sheeting with or without stretch for 24 h. The silicone membrane area was increased by 12% in stretched group. The cells without stretch served as control. Ito, IK1 and APD were recorded by the technique of whole-cell patch clamp. RESULTS：Compared with control group, Ito density in stretched myocytes was significantly reduced ［(16±04) pA/pF vs (121±29) pA/pF, P<001］, whereas IK1 density was increased ［(-108±08) pA/pF vs (-88±09) pA/pF, P<001］. The APDs at 50% and 90% levels of repolarization (APD50 and APD90) in the stretched cells were obviously decreased than those in non-stretched cells ［(105±14) ms vs (155±24) ms, (300±28) ms vs (563±36) ms, P<001］. CONCLUSION：Stretch stimulation leads to the reduction of Ito density, the increase in IK1 density and the shortness of APD in cultured rat atrial neonatal myocytes, which may contribute to atrial electrical remodeling induced by pressure overload.     

Electrophysiological effects of lidocaine on myocardial tissue in guinea-pig left ventricular outflow tract under conditions of hypoxia,acidosis and treatment with epinephrine

AIM：To study the electrophysiological effects of lidocaine on the myocardial tissue in guinea-pig left ventricular outflow tract under the conditions of hypoxia, acidosis and treatment with epinephrine. METHODS：The action potentials of pacemaker cells in guinea-pig left ventricular outflow tract were recorded by conventional technique with intracellular microelectrodes. The effects of lidocaine on the spontaneous slow response potentials were investigated under the conditions of hypoxia, acidosis and treatment with epinephrine (EPI). RESULTS：Lidocaine markedly decreased the rate of pacemaker firing (RPF), the velocity of diastolic depolarization (VDD), the maximal rate of depolarization (Vmax), the maximal diastolic potential (MDP) and the amplitude of action potential (APA). Lidocaine also shortened the 50% and 80% of duration of action potential (APD50 and APD80). At the concentrations from 0.1 μmol/L to 10 μmol/L, the effects of lidocaine were more significant. Under the condition of hypoxia and perfusion with deprived glucose content for 15 min, VDD, RPF, Vmax, MDP and APA significantly decreased, and APD50 notably shortened. Under the condition of hypoxia, lidocaine at 1 μmol/L significantly decreased VDD, RPF, Vmax and APA as compared with the cells treated with hypoxia only. Perfusion with pH 6.8 solution for 10 min, VDD, RPF, Vmax and APA significantly decreased, MDP notably increased, and APD50 and APD80 markedly shortened. Under the condition of acidosis for 10 min, lidocaine significantly decreased VDD, RPF and Vmax, and lengthened APD50 and APD80 as compared with the cells under the condition of acidosis alone. Perfusion with EPI at 10 μmol/L for 10 min resulted in significant increases in VDD, RPF, Vmax, MDP and APA, and notable shortenings of APD50 and APD80 were also observed. Compared with 10 μmol/L EPI group, 1 μmol/L lidocaine+10 μmol/L EPI significantly reduced VDD, RPF, MDP and APA, and lengthened APD50 and APD80. CONCLUSION：Lidocaine markedly decreases the autorhythmicity of the pacemaker cells in guinea-pig left ventricular outflow tract and influences the electrophysiological effects of hypoxia, acidosis and EPI.     

Synergistic effect of decitabine and valproic acid on apoptosis and cell cycle arrest at G0/G1 phase in gastric cancer MGC-803 cells

AIM: To investigate the synergistic effect of decitabine (DCA) and valproic acid (VPA) on apoptosis and cell cycle arrest at G₀/G₁ phase in gastric cancer MGC-803 cells. METHODS: Gastric cancer MGC-803 cells were used in the study and divided into the following groups according to the treatment with different drugs for 72 h: DCA 1.5 μmol/L,DCA 3.0 μmol/L, VPA 1.5 mmol/L, DCA 1.5 μmol/L+VPA 1.5 mmol/L and DCA 3.0 μmol/L+VPA 1.5 mmol/L. The early and late apoptotic rates were detected by annexin V and PI staining. The cell cycle was also determined by flow cytometry. The relative nm23-H1 mRNA expression level was measured by real-time quantitative PCR. RESULTS: The apoptotic rates in VPA 1.5 mmol/L+DCA 1.5 μmol/L group (early: 33.58%±3.88%; late: 31.52%±4.20%) and VPA 1.5 mmol/L+DCA 3.0 μmol/L group (early: 42.61%±4.23%; late: 38.01%±3.86%), the percentages of the cells in G₀/G₁ phase in VPA 1.5 mmol/L+DCA 1.5 μmol/L group (61.55%±2.38%) and VPA 1.5 mmol/L+DCA 3.0 μmol/L group (66.75%±2.48%), and the relative nm23-H1 mRNA expression levels in VPA 1.5 mmol/L +DCA 1.5 μmol/L group (1.84±0.46) and VPA 1.5 mmol/L+DCA 3.0 μmol/L group (3.02±0.36) were all significantly higher than those in the corresponding concentrations of single drug treatment groups (P<0.01). CONCLUSION: Synergistic effect of VPA and DCA on apoptosis and cell cycle arrest in gastric cancer MGC-803 cells is possibly via inactivation of nm23-H1 gene expression.     

Effect of panax notoginseng saponins on electrophysiological characteristic of atrial cardiomyocytes in guinea pig

AIM: To study the effect of panax notoginseng saponins on the left atrial appendage (LAA) of the guinea pigs. METHODS: Standard microelectrode intracellular recording technique was used to record the LAA action potential (AP) and the effective refractory period (ERP) in the guinea pigs during the pouring with different density of PNS. RESULTS: The effect of PNS in concentration of 0.7, 7, 70, 700 mg/L was significant at 20 min, the APD50 and APD80 of the pouring at 20 min, 30 min, 40 min of the 70 mg/L was longer than the reference group (P<0.05). The rest potential (RP), action potential amplitude (APA) and Vmax kept no change during the pouring at 20 min with 4 difference densities from 0.7 to 700 mg/L. The pouring at 20 min of 7 mg/L and 70 mg/L obviously prolonged the ERP of the atrial cardiomyocytes. compared to the reference group, it prolonged from (127.00±7.26) ms to (153.00±9.19) ms and (161.00±10.21) ms (P<0.01). However, pouring at 10 min with 7 000 mg/L caused the arrhythmias. CONCLUSION: PNS prolongs the APD and ERP in guinea pig atrial cardiomyocytes. It may be the mechanism of PNS against arrhythmias in cellular level, which is similar to amiodarone.     

Effect of BQ123 on the voltage-gated K+ current of pulmonary artery smooth muscle cells of rats exposed to chronic hypoxia

AIM:To study the effect of BQ123 on voltage-gated K+ current in pulmonary artery smooth muscle cells (PASMCs) from chronic hypoxic rats. METHODS:Twelve age and body weight matched Wistar rats were randomly divided into control and chronic hypoxic group. Single PASMCs were obtained with acute enzyme (collagnaseⅠ plus papain) dispersing method. Using the whole cell patch-clamp technique in freshly isolated PASMCs from normorxic and hypoxic rats, the effects of ET-1 and BQ123, a selective ETA receptor antagonist, on voltage-gated K+ current were recorded. RESULTS:(1) ET-1 (10-8 mol·L-1) caused inhibition of K+ current in PASMCs from normoxic and hypoxic rats. The effect of ET-1 on K+ current in PASMCs from hypoxic rats was greater than that from normoxic rats ［+50 mV, percent inhibition were (71.04±6.58)% and (60.21±5.32)%, respectively, P<0.01, n=6］. (2) In normoxic PASMCs, neither BQ123 alone produced influence on the IKV (P>0.05, n=5), nor ETA receptor blockade had change of ET-1 mediated IKV inhibition. (3) In chronic hypoxic PASMCs, BQ123 significantly reduced the effect of ET-1 mediated IKV inhibition, from (28.49±6.69) pA/pF to (74.19±9.74) pA/pF at +50 mV (P<0.01, n=6). CONCLUSION:In normoxic condition, the effect of ET-1 on IKV of PASMCs is not mediated by BQ123, a selective ETA receptor antagonist. During exposure to chronic hypoxia, the inhibition of ET-1 on IKV of PASMCs is partly mediated by BQ123, namely, ETA receptor mediates the effect of ET-1 on IKV of chronic hypoxic PASMCs.     

Angiotensin II-induced matrix metalloproteinase-9 expression mediated by NF-κB pathway in human THP-1 cells

AIM: The present study was undertaken to investigate the effect of angiotensin II (AngⅡ) on expression of MMP-9 in THP-1 macrophages. METHODS: Macrophages converted from THP-1 monocytes by incubating with PMA (0.1 μmol/L) for 48 h were divided into PMA group; PMA+AngⅡ group (10-7mol/L, 1 h); PMA+AngⅡ+PDTC group (10 μmol/L, 30 min) and PDTC group. Western blotting was used to detect the MMP-9 and phosphorylation of NF-κB p65, and the expression of MMP-9 mRNA in THP-1 macrophages was measured by RT-PCR.RESULTS: Compared to control group, the expression of MMP-9 (1.06±0.11, P<0.05) and phosphorylation of NF-κB p65 (1.02±0.10, P<0.05) in THP-1 macrophages were expressed when treated with AngⅡ (10-7mol/L); and the expression of MMP-9 mRNA were upregulated (1.22±0.08, P<0.05). However, NF-κB inhibitor PDTC reduced the NF-κB p65 (0.99±0.12, P<0.01) and MMP-9 (1.04±0.14, P<0.01) expressions and decreased the expression of MMP-9 mRNA (0.90±0.06,P<0.01). CONCLUSION: NF-κB signaling pathway contributes to the expression of MMP-9 in THP-1 macrophage induced by AngⅡ.     

Modulation of interleukin-2 on the positive effect of isoproterenol in the isolated cardiomyocytes

AIM: To explore the effects and mechanism of interleukin-2 (IL-2) on the positive effect of isoproterenol (ISO) in the isolated rat cardiomyocytes. METHODS: Enzymatically isolated cardiomyocytes were used. Peak twitch amplitude and maximal velocity of shortening/relaxation (±dL/dtmax) in the isolated cardiomyocytes were recorded with a microscope coupled to a charge-coupled device camera and ［Ca2+］i transients were determined with a fluorometric ratio method by using Fura-2/AM as Ca2+ indicators. RESULTS: ① ISO increased the peak twitch amplitude and ±dL/dtmax of the isolated cardiomyocytes. Perfusion for 15 min with IL-2 at 2×103 U/L, which had no effect at all, attenuated the enhancing effect of ISO on the peak twitch amplitude and ±dL/dtmax. ② ISO increased the ［Ca2+］i transients of the single ventricular myocytes in a dose dependent manner and the corresponding EC50 values of ISO was (0.12±0.01) μmol/L. Perfusion for 15 min with IL-2 at 2×103 U/L, which had no effect on the ［Ca2+］i transient at all, attenuated the enhancing effect of ISO and the corresponding EC50 was (0.44±0.06) μmol/L. ③ The electrically induced ［Ca2+］i transient was significantly increased by pretreatment with 20 mg/L cholera toxin for 12 h. The elevation of the ［Ca2+］i transient induced by cholera toxin was significantly attenuated by 2×103 U/L IL-2. ④ Forskolin (1 μmol/L), the activator of adenyl cyclase, significantly increased the electrically induced ［Ca2+］i transient, which was attenuated by IL-2 at 2×103 U/L. CONCLUSION: IL-2 inhibits the positive effect of isoproterenol in the isolated single ventricular myocytes, in which Gs protein and adenyl cyclase are involved.     

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.     

Effect of preconditioning with pioglitazone on ischemia reperfusion/hypoxia reoxygenation-induced mitochondrial structure and membrane potential in rats

AIM: To observe the effect of preconditioning with pioglitazone on ischemia reperfusion/hypoxia reoxygenation-induced mitochondrial ultramicro-structure and membrane potential in rats. METHODS: Sprague-Dawley rats were randomly divided into four groups: sham-operated (SO) group, ischemia reperfusion (IR) group, pioglitazone preconditioning group (Pio-P) and 5-HD+pioglitazone (5-HD+Pio) group. Apart from the SO group, IR, Pio-P and 5-HD+Pio groups were subjected to 30 min ischemia and 4 h reperfusion. The heart was quickly removed for observing the structure of mitochondria and measurement of the apoptosis index (AI) by TUNEL. Primary cultured cardiomyocytes of Sprague-Dawley rats were divided into control, hypoxic reoxygenation (HR) and different concentrations of Pio-P group. JC-1 staining flowcytometry was adopted to examine mitochondrial membrane potential (ΔΨm). RESULTS: The injury of mitochondrial structure in IR group was severer than that in Pio-P group, while the difference between 5-HD+Pio group and IR group was not evident. Flameng score in Pio-P group(1.62±0.60) was significantly lower than that in IR group (2.75±1.09), P<0.01. AI in Pio-P group (28.19%±4.93%) was lower than that in IR group (55.44%±6.63%),P<0.05. The rates of low ΔΨm cells in (5 μmol/L,10 μmol/L and 15 μmol/L) Pio-P group were (45.89±3.63)%, (17.13±1.37)% and (18.43±2.44)%, significantly lower than that in HR group (56.52%±2.87%),P<0.05, while the difference between 10 μmol/L group and 15 μmol/L group was not significant (P>0.05). CONCLUSION: Pioglitazone protects the heart from ischemia reperfusion/ hypoxia reoxygenation injury evidenced by improving mitochondrial ultrastructure and lessening the loss of mitochondrial membrane potential, and decreasing apoptosis. The cardioprotective effects can be inhibited by the blocker of mitochondrial ATP-sensitive potassium channels.     

Influence of leptin on intestinal function and its protective effect on hepa tic and renal functions after sepsis

AIM: To detect the effect of sepsis on hepatic,renal functions and corresponding enzymes in intestine of mice,and to explore the role of leptin in acute inflammation.METHODS: A mice model of sepsis was made by cecum ligation and perforation,and 96-well spectrophotometry was used to detecte the levels of alanine aminotransferase (ALT),uric acid (UA) and activities of myeloperoxidase (MPO),glutathin-S-transferase (GST),xanthine oxidase (XOD),superoxide dismutase (SOD) in serum and intestinal homogenized fluids,respectively.Hematoxylin-eosin staining was used simultaneously to check the histopathologic changes of intestine.RESULTS: Compared with sham group (330.12 μmol/L±94.15 μmol/L),serum UA level (521.92 μmol/L±91.86 μmol/L) at 6 h after sepsis was significantly higher.12 h after sepsis,both serum ALT (83.55 U/L±40.44 U/L) and UA (474.03 μmol/L±75.22 μmol/L) were significantly higher than those in sham group (66.23 U/L±16.80 U/L and 320.95 μmol/L±99.14 μmol/L,respectively).12 h after leptin injection (0.1 mg/kg,ip) or indomethacin injection (2 mg/kg,ip),the serum ALT and UA levels significantly decreased (vs sepsis group,P<0.05).Moreover,the activities of MPO,GST,XOD and SOD in intestine were changed at different degrees.CONCLUSION: During the process of sepsis,trace dose of leptin injected peritoneally significantly improves and stabilizes the hepatic and renal functions.The mechanisms may be related with those intestinal enzymes associated with metabolism of free radicals,mercapto group and purine.Indomethacin exerts a similar role as leptin though at much higher dose.     

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.     

Effects of sodium metabisulfite on sodium current in acutely isolated rat hippocampal CA1 neurons

AIM: To study the effects of sodium metabisulfite (SMB), sulfur dioxide (SO2) and its derivatives in vivo, sodium bisulfite and sulfite, on Na+ currents. The effects of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) against SMB were also studied in freshly dissociated hippocampal CA1 neurons in rats. METHODS: The whole-cell patch-clamp techniques were used in the experiments. RESULTS: ① SMB increased the voltage-activated Na+ currents in a concentration-and voltage-dependent manner. The amplitudes of Na+ currents was increased (22.36±3.28) % and (65.05±5.75)% (n=10) by SMB at 2 μmol/L and 20 μmol/L, respectively. ② SMB (10 μmol/L) did not affect the activation process, but changed the inactivation process significantly. Before and after application of 10 μmol/L SMB, the half-inactivation voltage was (-82.38±0.54) mV and (-69.39±0.41) mV (n=10, P<0.01). However, the slope factor remained unchanged. ③ SOD, CAT and GPx partly inhibited the incremental effect of SMB on Na+ currents. CONCLUSION: SMB increases Na+ currents and inhibits the steady-state inactivation, which contributes to the increase in the excitibility of neuronal cells. Its mechanism may involve oxidative damage caused by sulfur-and oxygen-centered free radicals in the rat hippocampal CA1 neurons.     

Effects of beta2-adrenergic blocker on cytosolic Ca2+ in isolated cardiomyocytes of rats with myocardial infarction

AIM: To investigate if beta2-adrenergic receptors result in more Ca2+ load after myocardial infarction (MI), the effects of beta2-adrenergic blocker on cytosolic Ca2+ (［Ca2+］i) were studied. METHODS: Male Wistar rats underwent a ligation of left coronary artery (n=9) or a sham operation (n=3). Cardiomyocytes were dissociated at 2, 4 and 8 weeks after MI and ［Ca2+］i was measured via fura-2 fluorescence. The response of cardiomyocytes to isoproterenol (1 μmol/L) in the presence or absence of atenolol (1 μmol/L), beta2-adrenergic blocker ICI118,551 (0.1 μmol/L) or propranolol (1 μmol/L) was examined. RESULTS: ICI118,551 suppressed the increase in ［Ca2+］i induced by isoproterenol at 4 and 8 weeks after MI (24.5%±5.7% vs 57.8%±13.2%, P<0.01; 12.2%±7.9% vs 44.6%±11.3%, P<0.01), but had no effects in control and 2 weeks post-MI groups. It decreased ［Ca2+］i in control and the three post-MI groups by 14.3%, 7.9%, 57.6% and 72.6%, respectively. Atenolol had suppressive effects only in control and 2 weeks post-MI groups (P<0.05). Propranolol had suppressive effects in control and all three post-MI groups (P<0.01). CONCLUSION: Beta 2-adrenergic blocker ICI118,551 exerts negative effects on ［Ca2+］i after MI, and the effects dramatically increase with the progression of MI.     

Electrophysiological changes in rat ventricular myocardium of experimental diabetes and action of CVB-D

AIM: To investigate the electrophysiological changes of diabetic myocardium and effects of cyclovirobuxine D (CVB-D) on its electrophysiology. METHODS: Diabetes was induced in male SD rats, using a single injection of alloxan into tail vein. Untreated age-matched animals were used as controls. Animal electrocardiogram (ECG) was recorded by 2 weeks. Effects of CVB-D on isolated right ventricular papillary muscle from experimental diabetic rats and control group were observed by recording the transmembrane potentials with conventional glass microelectrodes. RESULTS: QT intervals in ECG and action potential duration (APD) at all levels were significantly lengthened in myocardium from week 2 of diabetes. Within the concentration of 13.3-63.3 μmol·L^-1, CVB-D prologated APD of diabetes in dose-dependent manner and more than that of control. Within the concentration of 33.3-63.3 μmol·L^-1, CVB-D depressed RP, APA, Vmax and OS of diabetes in dose-dependent way and more than that of control. In addition, CVB-D at concentration of 20 μmol·L^-1 prologated APD in a time-dependent manner. The most prologation of APD was attained about 40 min in control, while more than 40 min in diabetes. CONCLUSION: The results show that QT intervals in ECG and APD at all levels are significantly lengthened in myocardium from week 2 of diabetes. CVB-D prolongates APD and inhibits RP, APA, OS and Vmax more in diabetes than in control.     

Effects of salvianolic acid B on the energy metabolism and hydrocephalus in mice with cerebral ischemia

AIM: To explore the effects of salvianolic acid B (SalB) on the energy metabolism and hydrocephalus in mice with cerebral ischemia.METHODS: NIH mice were randomly divided into four groups: sham-operated group,cerebral ischemia group,SalB-treated group and nimodipine-treated group.The brain tissue energy charge (EC),phosphocreatine (PCr),the activity of ATPase,excitability amino acid (EAA) content and water content of brain were measured when cerebral ischemia for 30 min.RESULTS: EC (0.520±0.034),PCr content ［(98.344±13.249) μmol/g］,the activity of Na⁺-K⁺-ATPase ［(0.593±0.013)×10³ U/g］ and Ca²⁺-ATPase ［(0.484±0.053)×10³ U/g］ in SalB-treated group were significantly higher than those in cerebral ischemia group {EC (0.465±0.037),PCr content ［(81.614±9.919) μmol/g］ ,the activity of Na⁺-K⁺-ATPase ［(0.244±0.065)×10³ U/g］,the activity of Ca²⁺-ATPase ［(0.321±0.086)×10³ U/g］} (P<0.01).The glutamate (Glu) content ［(0.405±0.110) μmol/g］,aspartate (Asp) content ［(0.141±0.020) μmol/g］ and water content of brain ［(38.1±0.1)%］ in SalB-treated group were markedly lower than those in cerebral ischemia group ［ Glu content (0.550±0.140) μmol/g,Asp content (0.287±0.050) μmol/g,water content of brain (44.1±0.1)%］ (P<0.05,P<0.01).CONCLUSION: The increase in cerebral energy metabolism and the activity of ATPase,and decrease in EAA content in brain tissue are the mechanism of SalB alleviating hydrocephalus at the early stage of cerebral ischemia in mice.