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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 (IK1), 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).IK1 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 IK1 channel.
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Aim To observe the effect of antibody NCX-3F10 on the main ion current of rat ventricular myocytes and its effect on arrhythmias induced by ischemia/reperfusion(I/R).Methods ① The whole-cell patch clamp technique was employed to record the Na+/Ca2+ exchange current(INa/Ca) and other major ion currents in rat ventricular myocytes.② The rat models of arrhythmia induced by ischemia/reperfusion were established by ligating the left coronary artery to in vivo and in vitro.Then the effects of antibody on the arrhythmia were observed.③ The IonOptix ion imaging system was used to observe the effect of antibody on calcium transients in single ventricular myocytes.Results ① The antibody NCX-3F10 dose-dependently inhibited INa/Ca from 5 to 40 mg·L-1.The IC50 for outward and inward currents was 11.15 and 11.69 mg·L-1, and the maximum inhibitory rates were 61% and 62%, respectively.The antibody also had an inhibitory effect on calcium current(ICa-L), and had no significant effect on inward rectifier potassium current(IK1), transient outward potassium current(Ito) and sodium current(INa).② In the isolated rat heart group I/R, 100% rats showed ventricular tachycardia, and 88.89% rats had ventricular fibrillation.After administration of antibody NCX-3F10(10 mg·L-1) 5 min before reperfusion, the incidence of ventricular tachycardia decreased to 44.43%(P<0.05), and the duration of ventricular tachycardia and ventricular fibrillation was also shortened remarkably(P<0.05).③ In the anesthetized rats after administration of antibody NCX-3F10(50 μg·kg-1) 5 min before reperfusion, the incidence and duration of ventricular tachycardia,the incidence and duration of ventricular fibrillation, and total number of ventricular premature beats were significantly decreased(P<0.05).④ From 5 to 40 mg·L-1, NCX-3F10 antibody decreased calcium transient amplitude in rat single ventricular myocytes dose-dependently(P<0.05).Conclusions The NCX-3F10 antibody shows significant arrhythmic effects on ischemia-reperfusion induced arrhythmia in rats both in vitro and in vivo, the underlying mechanism of which is related to NCX and L-type calcium current inhibition and calcium overload reduction by the NCX antibody.
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Aim To examine the effect of zacopride,a specific inward rectifier potassium channel(IK1)agonist,on L-thyroxine(T4)-induced ventricular remodeling and the underlying mechanism.Methods SD rats were randomly divided as control,L-thyroxine(L-thy,1 mg·kg-1·d-1,ig,10 d)model,L-thy +zacopride(5,15,50 μg·kg-1,respectively,ip),L-thy+zacopride(15 μg·kg-1)+chloroquine(7.5 μg·kg-1,ip)and L-thy+captopril(100 mg·kg-1·d-1,drinking water)groups.Echocardiography and cardiac hypertrophic indexes were measured to confirm the establishment of the ventricular remodeling model.The changes of IK1 and L-calcium current(ICa-L)were detected by whole cell patch clamp technique.The confocal microscopy and fluorescent indicator Fluo-4 were applied to examine the intracellular Ca2+ concentration([Ca2+]i)of isolated adult rat ventricular myocytes.Results L-thyroxine induced left ventricular hypertrophy with increased ratio of heart weight(HW)to body weight(HW·BW-1),ratio of left ventrical weight(LVW)to body weight(LVW·BW-1),left ventricular dimension in diastole(LVIDd),left ventricular dimension in systole(LVIDs),interventricular septum thickness(IVS)and decreased ejection fraction(EF),fractional shortening(FS)(P<0.01).Patch clamp data suggested IK1 was downregulated,while ICa-L was upregulated(P<0.01).In isolated adult cardiomyocytes,L-thyroxine increased the cell area and [Ca2+]i(P<0.01).Zacopride treatment obviously alleviated cardiac remodeling,improved cardiac function,reversed the changes of IK1 and ICa-L,and significantly attenuated intracellular calcium overload(P<0.01).The optimum dose of zacopride in vivo was 15 μg·kg-1 at which the effect was compared favourably with captopril,a classical anti-remodeling agent.Low-dose IK1 atagonist chloroquine could reverse the effect of zacopride(P<0.01).Conclusion Via activating IK1,zacopride could significantly decrease Ca2+ influx and intracellular calcium overload thereby inhibiting L-thyroxine-induced cardiac ventricular remodeling.
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Objective: To investigate the effect with its possible mechanisms of zacopride on vasodilatation of isolated coronary arterial rings in experimental rats. Methods: The tension of vasodilatation of isolated coronary arterial rings of male SD rats was recorded by Powerlab and DMT system. The rats were divided into 4 groups: +Endo (vehicle) group, +Endo (zacopride) group and -Endo (vehicle) group, –Endo (zacopride) group.n=6 in each group. The vasodilatation effects of zacopride on KCl (60 mmol/L) and U46619 (10-6 mol/L) pre-constricted arterial ring were recorded; the effects of different agents on zacopride caused vasodilatation were studied. Results: In both +Endo (zacopride) and –Endo (zacopride) groups, zacopride showed a dose dependent vasodilatation effect on coronary ring pre-constricted by KCl and U46619. The maximum vasodilatation effect of zacopride in KCl treated+Endo (zacopride) group was (90.15 ± 6.38) %, in U46619 treated-Endo (zacopride) group was (81.67 ± 4.97 ) %; the maximum vasodilatation effect of zacopride in KCl treated-Endo (zacopride) group was (85.48±5.04) %, in U46619 treated–Endo (zacopride) group was (79.65 ± 3.51) %, compared to each corresponding vehicle group, allP0.05. Conclusion: Zacopride had vasodilatation effect on coronary arterial ring which was pre-constricted by KCl and U46619, which might be related to the channel of IK1.
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Aim To assess the effects of N -[2-p-bromo-cinnamylamino-ethyl]-5-isoquinoline-sulfonamide (H-89), a potentially selective inhibitor of Protein Kinase A (PKA), on cardiac membrane ion channels and transporters, which will further fulfill our understanding of pharmacology of PKA inhibitors.Methods Whole-cell patch clamp was used to investigate the effects of H-89 on cardiac L-type Ca~(2+) current (I_(Ca-L)), Na~+ current (I_(Na)), inward rectifier K~+ current (I_(K1)), transient outward K~+ current (I_(to)) and Na~+-Ca~2+ exchanger current (I_(Na/Ca)) in enzymatic dissociated SD rat ventricular myocytes.Results H-89 at 1～10 μmol·L~(-1) could inhibit I_(Ca-L) , I_(Na) , and Ito in a concentration-relative manner (P <0.05). At low concentra-tion (5 μmol·L~(-1)), H-89 completely inhibited I_(K1) (P <0.05) just as the action of 0.5 mmol·L~(-1) BaCl_2.Further, H-89 at 1～10 μmol·L~(-1) had no significant effect on I_(Na/Ca) (P >0.05).Conclusion The direct or PKA-mediated indirect action maybe involved in the effects of H-89 on ion currents and transporter.
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Aim To investigate the effects of 5-HT_4 receptor agonist and 5-HT_3 receptor antagonist 2-[1-(4-piperonyl)piperazinyl]benzothiazole on rat heart rhythm and the involved ionic mechanisms.Methods Langendorff-perfused rat hearts were subjected to 0.1～10 μmol·L~(-1) 2-[1-(4-piperonyl)-piperazinyl]benzothiazole for 15 minutes with simultaneous ECGs recording.The whole-cell patch-clamp electrophysiology was used to record effects of 2-[1-(4-piperonyl)piperazinyl]benzothiazole on inward rectifier K~+ current(I_(K1)),transient outward K~+ current(I_(to)),resting membrane potential(RMP)and action potential(AP)in enzymatic dissociated rat ventricular myocytes.Results In ex vivo Langendorff-perfused hearts,0.1～10 μmol·L~(-1) 2-[1-(4-piperonyl)piperazinyl]benzothiazole elicited singnificant rhythm disturbances.In the presence of 10 μmol·L~(-1) agent,the total of PVB were 236±37,87.5%(7/8)hearts exhibited VT,and 62.5%(5/8)hearts exhibited VF(P<0.01).At the concentration of 0.1～10 μmol·L~(-1),2-[1-(4-piperonyl)piperazinyl]benzothiazole could inhibit I_(K1)(EC50=0.74 μmol·L~(-1))and I_(to)(EC50=2.16 μmol·L~(-1)),decrease RMP and prolong action potential duration(APD)in concentration-dependent manners(n=6,P<0.01).Conclusion Inhibition of IK1,Ito and resultant prolongation of APD,depolarization of RMP might be the critical causes for induction of arrhythmias by 2-[1-(4-piperonyl)piperazinyl]benzothiazole in rat.
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The changes in excitability and autorhthmicity of bladder detrusor in experimental noninsulin dependent diabetes mellitus (NIDDM) rats were observed. Sixty-nine NIDDM rats as NIDDM group and 69 normal rats as control group were enrolled into this experimental study. At 6th,10th, 14th, 18th, 22nd and 26th week after the rats were injected last time, the changes in the excitability and autorhthmicity of detrusor strips in vitro were observed. The results showed that the threshold of the tension which made the detrusor strips contract was significantly higher in NIDDM group (0.716±0.325 g) than in control group (0.323±0.177 g)(F=59.63, P＜0.001). At different stages, the threshold of the tension resulting the contract of the detrusor strips in NIDDM group was also higher than in control group. At 18th week after STZ injection, the frequency of spontaneous contract of the detrusor strips in NIDDM was significantly higher than in control group (P＜0.05), whereas at 22nd week, that in NIDDM group was significantly lower than in control group (P＜0.05). It was concluded that the decreased excitability of the bladder detrusor was the earliest and most obvious changes in bladder function in diabetes rats and the autorhthmicity had also changed at the early stage of diabetic bladder.
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The changes in excitability and autorhthmicity of bladder detrusor in experimental non-insulin dependent diabetes mellitus (NIDDM) rats were observed. Sixty-nine NIDDM rats as NIDDM group and 69 normal rats as control group were enrolled into this experimental study. At 6th, 10th, 14th, 18th, 22nd and 26th week after the rats were injected last time, the changes in the excitability and autorhthmicity of detrusor strips in vitro were observed. The results showed that the threshold of the tension which made the detrusor strips contract was significantly higher in NIDDM group (0.716 +/- 0.325 g) than in control group (0.323 +/- 0.177 g) (F = 59.63, P < 0.001). At different stages, the threshold of the tension resulting the contract of the detrusor strips in NIDDM group was also higher than in control group. At 18th week after STZ injection, the frequency of spontaneous contract of the detrusor strips in NIDDM was significantly higher than in control group (P < 0.05), whereas at 22nd week, that in NIDDM group was significantly lower than in control group (P < 0.05). It was concluded that the decreased excitability of the bladder detrusor was the earliest and most obvious changes in bladder function in diabetes rats and the autorhthmicity had also changed at the early stage of diabetic bladder.
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Diabetes Mellitus, Experimental/physiopathology , Diabetes Mellitus, Type 2/physiopathology , Muscle Contraction/physiology , Muscle Relaxation/physiology , Rats, Wistar , Urinary Bladder/physiopathology , Urinary Bladder Diseases/etiology , Urinary Bladder Diseases/physiopathologyABSTRACT
AIMTo elucidate possible mechanisms underlying the differences between 1S-[1a,2b,3b,4a(S*)]-4-[7-[[1-(3-chloro-2-thienyl)methylpropyl]propyl-amino]-3H-imidazo[4,5-b]pyridyl-3-yl]-N-ethyl-2,3-dihydroxycyclopentane carboxamide (AMP- 579) and adenosine in pharmacological and clinical effects. METHODSNa+/Ca2+ exchange current was recorded by patch-clamp technique in whole-cell configuration. RESULTSAMP579 significantly enhanced both outward and inward Na+/Ca2+ exchange currents in a concentration dependent manner. Neither infusion of an adenosine A1 receptor antagonist PD116948 30 μmol*L-1 or an adenosine A2 receptor antagonist DMPX 10 μmol*L-1 nor a protein kinase A special blocker KT 5720 0.2 μmol*L-1 or a protein kinase C special blocker GF 109203X 0.4 μmol*L-1 had effect on Na+/Ca2+exchange current increased by AMP579, suggesting that AMP579 possess a direct activating effect on Na+/Ca2+ exchange current. CONCLUSIONAMP579 possibly possesses a direct activating effect on Na+/Ca2+ exchange current.
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Aim This paper aims at investigating the effect of dofetilide on Na+/Ca 2+exchange in ventricular myocytes of adult guinea pigs. Methods Rapid enzymatic isolation procedure was performed to get single ventricular myocytes from adult guinea pigs. After the whole cell configuration was formed, a ramp voltage-clamp pulse depolarized from a holding potential of -40 mV to +60 mV, then hyperpolarized to -120 mV at a rate of 90 mV/s to record the Na+/Ca 2+ exchange current (I Na/Ca) and the influence of dofetilide from 0.03～1.0 ?mol?L -1. Result Dofetilide from 0.03～1.0 ?mol?L -1 concentration-dependently increased the I Na/Ca in both outward and inward mode. The EC 50 of dofetilide on I Na/Ca in outward and inward mode of NCE was 0.178 ?mol?L -1 (95% confidence interval was 0.040～0.787 ?mol?L -1) and 0.178 ?mol?L -1 (95% confidence interval was 0.038～0.842 ?mol?L -1), respectively. Conclusion Dofetilide concentration-dependently increased the outward and inward Na+/Ca 2+ exchange current in ventricular myocytes of adult guinea pigs.
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<p><b>OBJECTIVE</b>To investigate the importance of autoimmunity against beta(1)-adrenoreceptor in the pathogenesis of dilated cardiomyopathy (DCM).</p><p><b>METHODS</b>Fourteen rabbits were divided equally into two groups. Rabbits in the immunized group (n = 7) were immunized monthly for one year with synthetic peptide corresponding to the second extracellular loop of the beta(1)-adrenoreceptor and adjuvant. Control rabbits received the mixture with the same procedure as described except with a substitution of saline for the corresponding peptide. During the study period, all rabbits were bled to assay the titers of antipeptide antibody and left ventricular ejection fractions (LVEFs) were measured by emission computed tomography. At the end of experiment, invasive cardiac function was measured and morphologic examinations were done.</p><p><b>RESULTS</b>High titers of antipeptide antibody were found in the sera from immunized rabbits throughout the study period in contrast to those from control rabbits. LVEFs were significantly higher in immunized rabbits than those of the control group at the 4th and 6th month. At the end of the experiment, the maximal rates of rise and decline of ventricular pressure of the immunized group were significantly lower than those of the control group. Morphological changes were found in immunized rabbits such as the enlargement of ventricles, myofibrillar lysis and necrosis, mitochondria swelling and condensation. No obvious alterations were noted in hearts of control rabbits.</p><p><b>CONCLUSION</b>Autoimmunity against the beta(1)-adrenoreceptor may be involved in the pathogenesis of dilated cardiomyopathy and beta(1)-adrenoreceptor antibody may play a role in the process.</p>
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Animals , Male , Rabbits , Cardiomyopathy, Dilated , Allergy and Immunology , Pathology , Heart , Immunization , Microscopy, Electron , Myocardium , Pathology , Peptide Fragments , Allergy and Immunology , Receptors, Adrenergic, beta-1 , Chemistry , Allergy and Immunology , Ventricular Dysfunction, LeftABSTRACT
AIM To study the effects of Phe-Met-Arg-Phe-NH2 (FMRFa) on Na+/Ca2+ exchange and its specificity for Na+/Ca2+ exchange in rat ventricular myocytes. METHODS Na+/Ca2+ exchange current and other currents of ion channels were measured using whole cell voltage clamp techniques. RESULTS A dose-related inhibition of tetrapeptide FMRFa on Na+/Ca2+ exchange was observed in rat ventricular myocytes. Inward and outward INa+/Ca2+ were inhibited by 60.1% and 56.5%, respectively, at highest concentration (100 μmol*L-1) and its IC50 were 20 μmol*L-1 and 34 μmol*L-1 in inward and outward INa+/Ca2+, respectively. Inward and outward INa+/Ca2+ were inhibited 38.7% and 34.9%, respectively, at FMRFa 5 μmol*L-1. FMRFa 5 μmol*L-1 and 20 μmol*L-1 did not affect L-type calcium current, sodium current, transient outward current and inward rectifier potassium current. CONCLUSION These data indicate that FMRFa is a specific inhibitor of Na+/Ca2+ exchange in intact rat ventricular myocytes.
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150 ml in 22 patients (31%).Ten patients (14%) had detru-sor instability.Six patients were incapable to void during the test. The volume of first bladder sensation was(203.25?107.53)ml (range,125 -630 ml) in the diabetes patients.The bladder capacity was (428.09?227.89)ml (range,220 -1350 ml).The maximum flow rate was (10.70?3.27) ml/min.The residualurine volume was (100.57?108.08) ml.In early stage group the volume of first bladder sensation was(151.67?24.07) ml;while in progressive stage group it was (268.16?13.90)ml,and bladder capacitywas (592.97?252.51)ml.The maximum flow rate was (8.61?2.04) ml/min. PQmax was (33.16?19.81)cm H2O (1 cm H2O=0.098 kPa).The residual urine volume was (169.03?137.25) ml. Theseparameters were all abnormal. In the detrusor strips test,the threshold of the tension which made the detrusorstrips contract was significantly higher in T2DM rats [(0.72?0.33) g] than in control rats [(0.32?0.18)g] (F=59.63,P
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0.05).Zacopride at concentration of 1.0 ?mol/L showed the most potent activity on IK1 with approximately 30% increment both in inward current and outward current(P
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1∶640) was purified by affinity chromatography with a Mab Trap kit.The effects of the purified IgGs on the ion channel and transporter(INa/Ca,INa pump,ICa-L,Itko,Ik1,IK) at concentrations of 10 nmol/L,20 nmol/L and 40 nmol/L were observed by whole cell voltage clamp technique.RESULTS:The purified IgG enhanced INa/Ca,ICa-L and I Na/k pump in a dose-dependent manner and no significant effect on INa,Itko,Ik1 and Ik was found.CONCLUSION:The site specific antibody of Na-Ca exchanger stimulates Na-Ca exchanger current and has cross-reaction with L-type Ca channel and Na pump.
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AIM To investigate the positive inotropic effect of aconitine on isolated hearts from cardiac dysfunctional rats when combined with pinacidil. METHODS In our experiment Langendorff perfusion equipment was used to investigate the following cardiac indexes:LVSP(left ventricular systolic pressure), LVDP(left ventricular diastolic pressure), +d p /d t max (the maximum going up rate of left ventricular pressure) and -d p /d t max (the maximum going down rate of left ventricular pressure) from rat hearts under two conditions:① aconitine only,② aconitine plus pinacidil(an agonist of K ATP channel) to observe the positive inotropic effect of aconitine on cardiac dysfunctional rat hearts. RESULS ①Aconitine had certain positive inotropic effect on isolated hearts from cardiac dysfunctional rats; ②Combing aconitine with potassium channel activator markedly winded the doses range between the effective and toxic concentration and enhanced the cardiotonic effect of aconitine. CONCLUSION Aconitine had positive inotropic effect on dysfunctional isolated rat hearts; the combination of aconitine with potassium channel activator markedly widened the cardiotonic doses range of aconitine and enhanced its cardiotonic effect.
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Objective:To observe the effects of active immunization with a synthesized repetitive peptides in the extracellular loops of Na/Ca exchanger(NCX)?1 on cardiac structure and function in rats.Methods:A repetitive peptide of 124 HNFTAGDLGPSTIVGSAAFNMF145 was synthesized,which was in line with the extracellular loops of Na/Ca exchanger(NCX)?1.Healthly male Wistar rats of 2 month age were immunized actively with the synthesized peptide as antigen repeated for 12 weeks.The control group was given Freund's adjuvant only.Specific antibodies were detected by ELISA.The cardiac function was observed by Langendorff isolated heart-perfusing assay and the hearts were prepared for routine histological evaluation.Results:All rats immunized with the peptide developed highly positive autoimmunities,indicated by the antibody titers.After 12 weeks of peptide inoculation,the cardiac functioning indexes including LVSP-LVDP,+dp/dtmax and -dp/dtmax increased much more significantly in immunized group than in control.Histological evaluation showed that the myofilaments of the control group arranged regularly and densely with better continuity,whereas the myofilaments of the immunized group were lined with disorder.Some of those were ruptured.The interstitial lymphocyte infiltration was observed.Conclusion:The results indicate that long term immunization with the synthesized repeatitive peptide in line with the extracellular parts of Na/Ca exchanger(NCX)?1 can enhance both systolic and diastolic function of rat heart,but it can also induce injury in the heart structure.This may relate with an increase of myocardial oxygen consumption owing to a long time and continued excitement of membrane ion transporters as well as their active effect in heart contraction to a larger extent.
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Aim This study aimed at investigating the postconditioning protective effect of KB-R7943 and the proper administration time on cardiac ischemia-reperfusion injury in isolated rat heart. Methods Rat heart was isolated quickly when the animal was anesthetized. With Langendorff perfusion, the left anterior descending coronary artery was ligated for 30 min, then released for 120 min in isolated rat heart. Left ventricular function (LVF) and the infarct size of left ventricle were determined. Result Compared with control, KB-R7943 at 1 ?mol?L-1 perfused during the early period of the reperfusion prevented the post-ischemic depression of LVF, decreased the infarct size by 77 %(P