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Aim To investigate the effect of U50488H(a selective κ-opioid receptor agonist)and isoproterenol(ISO,a β-adrenergic receptor agonist)on ventricular arrhythmias and Cx43 during myocardial ischemia and reperfusion in rats.Methods 60 rats were randomly divided into five groups,ie,normal control group,I/R group,ISO+I/R group,U50488H+ISO+I/R group,Nor-BNI+U50488H+ISO+I/R group.The incidence of ventricular arrhythmias and arrhythmia score were determined. The expression of Cx43mRNA was tested by RT-PCR.The expression of Cx43 protein in myocardial cell was tested by an immunohistochemical approach with a quantitative imaging system.Results ① Compared with the I/R group,arrhythmia score was increased with administration of ISO(P<0.05).U50488H intravenously injected before ISO significantly decreased the arrhythmia score(P<0.05).② Compared with the normal control group,the expression of Cx43 mRNA was decreased in the I/R group(P<0.05).With administration of ISO,the amount of Cx43 mRNA was not significantly increased.③ Compared with normal control group,total and phosphorylated Cx43 proteins were significantly decreased in the I/R group(P<0.05),and the phosphorylated Cx43 was also decreased with administration of ISO.Compared with ISO+I/R group,phosphorylated Cx43 was increased with administration of U50488H (P<0.05).Conclusion κ-opioid receptor agonist U50488 H antagonizes the arrhythmias through the regulation of Cx43 during myocardial ischemia and reperfusion via inhibiting β-adrenergic receptor pathway.
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@#ObjectiveTo observe the growth of BT-325 human glioma cells after interfering volume-regulated chloride channel ClC-2 gene.MethodsTwo expression recombinant vectors of ClC-2 gene were designed and constructed. The primary plasmid, pSUPER.puro-shRNA, and the two recombinant plasmids, pSUPER.puro-shRNA-ClC-21 and pSUPER.puro-shRNA-ClC-22, were transfected into BT-325 cells by LipofectamineTM2000 (Groups: control, PP1 and PP2, respectively). The mRNA expression of ClC-2 gene was detected with reverse transcription polymerasse chain reaction (RT-PCR), the cellular survival was determined with MTT assay, and the cell cycle was measured with flow cytometry (FCM). ResultsClC-2 mRNA expression and the growth of the cells in PP1 and PP2 groups were significantly lower than that of control group. The cell cycle progression was blocked in G1 phase (PP1 and PP2 vs control,P<0.01). ConclusionThe growth of BT-325 human glioma cells is prevented by knockdown of ClC-2 gene expression, which may be one of the novel targets to inhibit growth of human malignant glioma cells.
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Aim To examine the effect of ? opioid receptor agonist U50488H on the levels of interleukin-6(IL-6) and interleukin-8(IL-8) from angiotensinⅡ(AngⅡ) stimulated endothelial cells.Methods In the in vivo study,the modulation of U50488H(1.5 mg?kg~-1) intravenously on the level of AngⅡ was evaluated.In the in vitro study,endothelial cells from human umbilical vein(HUVEC) were cultured and divided into four groups:Control group,AngⅡ group,and AngⅡ plus U50488H and/or nor-BNI(a selective ? opioid receptor antagonist) group.These groups were treated respectively with phosphate buffered solution(PBS),AngⅡ(10~-9~10~-5 mol?L~-1),and AngⅡ in the presence of U50488H and/or nor-BNI for 0~24 hours.Culture supernatant and endothelial cells were collected at 0,3,6,12 and 24 h.IL-6 and IL8 levels in culture supernatant were measured by enzyme linked immunosorbent assay(ELISA).Results The level of AngⅡ in the blood was significantly decreased following U50488H intravenously,which was blocked by nor-BNI administration(2 mg?kg~-1).AngⅡ stimulated the productions of IL-6 and IL-8 from HUVEC in the dose-dependent and time-dependent manners.U50488H at 10~-5 mol?L~-1 significantly inhibited this process,and the inhibitory effect of U50488H was blocked by nor-BNI,which itself had no effect.Conclusion ? opioid receptor may play a role in the process of anti-inflammation via down regulation of AngⅡ level and inhibition of the AngⅡ-stimulated IL-6 and IL-8 productions from endothelium cells.
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AIM:To investigate effect of hypoxia on the expression of proliferating cell nuclear antigen(PCNA) a nd phenotype of cardiac fibroblasts(CFs). METHODS: The purif ied cardiac fibro blasts were cultured and divided randomly into there groups :control group, mode rate hypoxia(MH) group and severe hypoxia(SH) group. After 72 h,MTT method was u s ed to investigate the proliferation of CFs, and the ultrastructure of fibroblast s were observed with transmission electron microscopy The expression of PCNA a n d ?-actin in cardiac fibroblasts were measured by the means of immunohistochemi s try and laser scanning confocal microscopy, respectively. RESULTS: MTT A 490 nm value of MH group was significantly higher than that of control group by (18 4?25 0)% ( P
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Objective To investigate the effects of quiet respiratory intrathoracic pressure changes on ventricular dimensions and left ventricular systolic function,and to further verify our newly proposed hypothesis of the mechanism of respiratory effects on hemodynamics.Methods Twenty healthy volunteers aged 18 to 40 years average(24?7) years were included.The respiratory curve and electrocardiogram were simultaneously recorded.The interventricular septum movement,ventricular dimensions and ventricular systolic excursions were recorded by two-dimensional and M-mode echocardiography during quiet respiration.The respiratory variations of the above parameters were derived,and the parameters for assessing ventricular systolic function were calculated.Results With quiet respiration,the interventricular septum moved towards the left ventricle on inspiration,and then towards the right ventricle on expiration.The right ventricular diastolic dimension increased significantly on inspiration compared with those on expiration.The opposite changes occurred with left ventricular diastolic dimensions.The left ventricular posterior wall systolic excursion and the left ventricular stroke volume significantly increased during expiration compared with those during inspiration.No significant differences were found in left ventricular ejection fraction and fractional shortening between inspiration and expiration.Conclusions The respiratory intrathoracic pressure change is one of the factors influencing the reciprocal changes of the left and right ventricular parameters related to ventricular dimensions and systolic function.
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Intracoronary effects of calcitonin gene related peptide (CGRP) on coro-nary hemodynamics were observed in the normal and following different extent of coro-nary stenosis using graded coropary- stenosis modl in dogs. The results showed that CGRPincreased the coronary artery blood flow (CBF) and distant coronary blood prepsure (DCP),but decreased mean artery pressure (MAP), coronary vessels total resistance (R_T),large co-ronary vessels, resistance (R_L) and small coronary vessels resistance (R_s). Thirty minutesafter. coronary middle. stenosis, CGRP was given intracoronary, MAP had no significantchange, but CBF insreased and R_T R_L, R_s decreased, and which maintained for 30 min. 30min after coronary severe stenosis, CGRP increased CBF and MAP, but decreased DCP,R_T, R_L, R_S continuously. These results suggested that CGRP could ameliorate myocardialischemia through enlargement of coronary vessels and by increasing CBF.
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Aim To investigate the effects of U50488H,a selective ?-opioid receptor agonist,on the blood pressure in the rats and explore their mechanisms.Methods Heart rate(HR),arterial blood pressure(ABP),left ventricular pressure(LVP),contractive function(+ dp/dt_(max)) and diastolic function(-dp/dt_(max)) were examined in rats.Physiological experimental technique was used to collect urine and to determine the volume of urine output;isolated artery perfusion technique was used to investigate the direct action of U50488H on abdominal aorta of rats.Results HR,ABP,LVP and ?dp/dt_(max) in rats were decreased with the administration of U50488H;the urine volume increased significantly with the administration of U50488H.U50488H induced a dose-dependent vasodilation in the aortic artery.These effects of U50488H were totally abolished by nor-BNI,a selective ?-opioid receptor antagonist.Conclusion Stimulation of ?-opioid receptor with U50488H depresses the blood pressure mainly by reducing the strength of cardiac muscle,enhancing the urine volume and relaxing the vessel.
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Aim To investigate the effects of U50,488H(a selective ?-opioid receptor agonist)on ventricular arrhythmias induced by myocardial ischemia and reperfusion in rats and to elucidate their mechanisms.Methods The contents of CK(creatine phosphokinase)and LDH(lactate dehydrogenase)were measured; The isolated heart was perfused using langendorff equipment. Heart rate(HR), arterial blood pressure(ABP), left ventricular pressure (LVP), cardiac function (?dp/dtmax), rate of ventricular tachycardia(VT)and ventricular fibrillation(VF)were examined in rats in vitro. The incidence of ventricular arrhythmias and arrhythmia score were also determined; The change of sodium currents (INa) induced by U50,488H was detected by whole-cell recording mode using patch clamp.Results ① In comparison with I/R group, the contents of CK、LDH in plasma of rats in U50,488H+I/R group were significantly lowered(P
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AIM: The present study was to investigate the time course of ?-adrenoceptor desensitization and changes in the calcium transient in rat ventricular myocytes following chronic hypoxia. METHODS: With the spectrofluorometric method, the intracellular calcium( i) transient and its response to ?-adrenoceptor stimulation were determined in the single right ventricular myocytes, loaded with Fura-2.RESULTS: After 2-3 weeks of chronic hypoxia, the amplitudes of electrically induced i transient and caffeine-induced i transient started to decrease and the duration of i transient prolonged. The enhanced electrically induced i transient evoked by isoprotrenol was also decreased. After 3 or 4 weeks of chronic hypoxia, these changes aggravated gradually. After 8 weeks of chronic hypoxia, the changes of all these parameters were convalescent, meanwhile there was no significant difference compared with that of 4 weeks group. CONCLUSIONS: After 2-4 weeks of chronic hypoxia, the ?-adrenoceptor desensitization occurs, the underlying mechanism is related to the decreased function of L-type of calcium channel, ryanodine receptor-operated calcium channel and calcium ATPase, which is responsible for the decreased cardiac functionl. At 8 weeks of hypoxia, the heart is in adaptation and compensatory process.
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AIM: To observe the changes of NO, ET-1, SOD and MDA levels in plasma of rats exposed to infrasound. METHODS: Using infrasound (frequency: 8 Hz; sound pressure level:130 dB), the rats were exposed for 1 d, 7 d, 14 d, 21 d and 28 d, 2 h daily, then the levels of NO, ET-1, SOD and MDA were measured after exposure. RESULTS: The changes of NO levels in plasma significantly declined at 7 d and 14 d (P0.05). The changes of ET-1 levels in all groups in plasma were significantly increased (P
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Aim To investigate the anti-arrhythmic effect and mechanism of ?-opioid receptor during myocardial ischemia and reperfusion in rats,and to initially determine the regulation of U50488H(U50,a selective ?-opioid receptor agonist) to angiotensinⅡ(AngⅡ),endothelin(ET) and nitric oxide(NO) in rats.Methods Rats were randomly divided into 7 groups,i.e.,control group,ischemia/reperfusion group(I/R),U50488H+I/R group,PTX group(PTX,a Gi/o proteininhibitor),Glib group(glibenclamide,a K_(ATP) channel blocker),Che group(chelerythrine,a selective PKC inhibitor),and Gen group(Genistein,a Tyrosine kinase inhibitor) respectively.The arrhythmia occurrence and score in different groups were observed and counted.The contents of AngⅡ,ET and NO in plasma of rats were also examined.Results ① Compared with I/R group,the arrhythmia score of U50+I/R group was significantly decreased.The effect of pared with I/R group,the arrhythmia score of U50+I/R group was significantly decreased.The effect of glibenclamide and chelerythrine respectively,the anti-arrhythmic effects induced by U50488H in the rats during myocardial ischemia and reperfusion were significantly attenuated or even completely blocked.③ The anti-arrhythmic effects of U50488H were not significantly affected by pretreatment with genistein.④ In comparison with normal rats,the contents of AngⅡand ET in plasma of I/R group were significantly increased,but the content of NO was decreased.With the administration of U50488H,the contents of AngⅡand ET in plasma of rats in U50488H+I/R group were significantly decreased.Meantime the content of NO was increased.Conclusions ① U50488H-induced anti-arrhythmic effects in the rats with myocardial ischemia and reperfusion are mediated by ?-opioid receptor.The signaling pathway may be related with(Gi/o,) PKC,and K_(ATP) channel.② The activation of ?-opioid receptor may elicit anti-arrhythmic effect through the down-regulations of AngⅡ or ET and up-regulation of NO in plasma of rats.
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To determine the regulatory effect of ? opioid receptor stimulation on ? adrenoceptor signaling and its underlying mechanism, single ventricular myocytes were isolated from the heart of rat subjected to chronic hypoxia for 4 weeks. The electrically induced [Ca 2+ ] i transient were measured using a spectrofluorometric method. RT PCR was used to determine the mRNA of ? opioid receptor, and Western blot was used to determine the Gi and Gs protein. ? adrenoceptor stimulation with isoproterenol increased the amplitude of the electrically induced [Ca 2+ ] i transient in myocytes of normoxic rats. U50488H, a selective ? opioid receptor agonist, significantly inhibited the effect of isoproterenol. In the heart of chronically hypoxic rats, the inhibition of U50488H was blunted. RT PCR revealed no significant change in mRNA of ? opioid receptor. Western blot showed no change in Gi protein. While biologically active Gs small protein decreased significantly. The results indicate that the negative modulation of ? opioid receptor on ? adrenoceptor is attenuated in the heart of chronically hypoxic rat. The decrease in Gs protein may be partially responsible for the attenuation.