Effects of metoprolol on electrophysiology of ischemic and anoxic myocardium in diabetic rats / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To investigate the effects of metoprolol on electrophysiology of ischemic and anoxic myocardium in diabetic rats.</p><p><b>METHODS</b>Forty Sprague-Dawley (SD) rats were divided into 4 groups: diabetes group; diabetes and ablation of left sympathetic nerve group; diabetes and metoprolol group and sham group. The diabetes model was induced by intraperitoneal injection of streptozotocin (STZ, 60 mg/kg). The ventricular diastolic effective threshold (DET), effective refractive period (ERP), and Ventricular fibrillation threshold (VFT) were measured. The serum concentration of nerve growth factor (NGF) was measured.</p><p><b>RESULTS</b>Metoprolol increased DET of ischemic and anoxic myocardium in diabetic rats. The ablation of the left sympathetic nerve increased VFT of diabetic rats. VFT in metoprolo group was significantly increased compared to diabetes group after ischemia. The concentrations of NGF in diabetic group and metoprolol group were higher than those in sham group. There were no difference in NGF levels between ablation of left sympathetic nerve group and sham group.</p><p><b>CONCLUSION</b>The remodeling of sympathetic nerve affects the electrophysiology of ischemic myocardium of diabetic rats. Metoprolol can increase the VFT and decrease the excitation threshold of the ischemic myocardium in diabetic rats.</p>

Involvement of potassium channel in hemin-induced cardioprotection in rat hearts / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To investigate the effects of heme oxygenase 1 inducer hemin on protection of ischemia-reperfusion injury in rats and its mechanisms.</p><p><b>METHODS</b>The Langendorff model of isolated rat heart was used; the left anterior descending coronary artery was occluded for 30 min and subsequently reperfused for 2 h. Then the ventricular function and infarct size were measured.</p><p><b>RESULT</b>Hemin preconditioning prevented the increase in LVEDP, decrease in LVDP and +/- dp/dt(max) in the isolated ischemia-reperfusion rat hearts. The leakage of LDH and CK in the coronary effluent was significantly declined in hemin-treated rat hearts. And the infarct size was also reduced. Administration of a blocker of mitochondrial ATP-sensitive potassium channel (mitoK(ATP)) 5-HD (5 mg/kg) before hemin preconditioning increased the LVEDP, and reduced the LVDP and +/- dp/dt(max). The leakage of LDH and CK in the coronary effluent and the infarct size were also increased compared with only hemin-treated rat hearts. Pretreatment of the rats with a blocker of sarcolemmal ATP-sensitive potassium channel (sarcK(ATP)) HMR-1098 (6 mg/kg) before hemin preconditioning also abolished the protective effect. Infusion of paxilline (1 micromol/L), a blocker of calcium activated potassium channel (K(Ca)) for 10 min before ischemia/reperfusion led to larger infarct size and poorer myocardial performance as compared with the hemin group. The leakage of LDH and CK in the coronary effluent was also increased.</p><p><b>CONCLUSION</b>Both mitoK(ATP)and sarcK(ATP)channels activation are required for the delayed cardioprotection induced by hemin. The opening of K(Ca) channels-dependent mechanism may be involved in the protection.</p>

Role of reactive oxygen species, nitric oxide and mitochondrial K(ATP) channels in TNF-alpha induced cardioprotection / 中国应用生理学杂志

<p><b>AIM</b>To explore the cardiac effect of TNF-alpha in postischemic heart and the possible mechanism.</p><p><b>METHODS</b>Langendorff perfused rat heart was used to evaluate the contractile properties of myocardium by intraventricular pressure measurement. The isolated rat heart underwent 20 min of global ischemia followed by 20 min of reperfusion. The level of lactate dehydrogenase (LDH) in the coronary effluent was measured to evaluate the cardiac injury. And the activity of manganese superoxide dismutase (Mn-SOD) in myocardium was measured.</p><p><b>RESULTS</b>Perfusion with TNF-alpha (104 U/L) attenuated the inhibitory effects induced by ischemia/reperfusion on left ventricular developed pressure (LVDP), left ventricular end-diastolic pressure(LVEDP), maximal rise/fall rate of left ventricular pressure (+/- dP/dtmax) and rate pressure product (LVDP multiplied by heart rate, LVDP x HR). TNF-alpha significantly decreased the release of LDH (P < 0.05) and increased the activity of Mn-SOD in the myocardium (P < 0.05). Antioxidant 2-MPG (0.3 mmol/L), NOS inhibitor L-NAME (0.5 mmol/L) or mitochondrial selective KATP channel inhibitor 5-HD (100 micromol/L) attenuated the increase in LVDP, +/- dP/dtmax and LVDP x HR, and decrease in LVEDP induced by TNF-alpha in ischemia/reperfusion heart, respectively. And the effects of TNF-alpha in reducing the levels of LDH and increasing the Mn-SOD activity were also attenuated by 2-MPG, L-NAME or 5-HD, respectively.</p><p><b>CONCLUSION</b>TNF-alpha pretreatment attenuates the myocardial injury induced by ischemia/reperfusion, which coincides with the increasing of myocardial Mn-SOD activity. Reactive oxygen species, nitric oxide and mitochondrial KATP channels are involved in the cardioprotection induced by TNF-alpha.</p>

Modulation of iron on the vasodilating effect of interleukin-2 in the isolated aortic ring / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To explore the effect and mechanism of iron on the vasodilating effect of interleukin-2 (IL-2) in the isolated aortic ring.</p><p><b>METHODS</b>Isometric tension was recorded in response to drugs in organ bath. Ferric ammonium citrate (FAC) was added to the bath 30 min before phenylephrine (1 micromol/L), which was followed by IL-2 in a cumulative fashion. Spectrophotometry was used to determine the activity of nitric oxide synthase (NOS) of the thoracic aorta.</p><p><b>RESULTS</b>FAC (0.1 - 10 micromol/L) alone did not affect the tension of rings,but inhibited the vasodilating effect of IL-2 (1 - 1,000 U/ml) in a dose dependent manner. IL-2(1, 10, 100, 1000 U/ml) decreased the aortic tension to (78.47+/-4.31)%, (66.86+/-5.55)%, (52.62+/-4.51)% and (42.39+/-4.27)% of pre-drug control, respectively. However, after incubation with 10 micromol/L FAC in the presence of IL-2, the aortic tension was reduced to (89.81+/-1.94)%, (86.13+/-3.11)%, (77.16+/-5.66)% and (68.76+/-5.69)% of pre-drug control, respectively. Pretreatment with L-arginine (1 mmol/L) abolished the inhibitory effect of FAC. Pretreatment with FAC attenuated the increased activity of NOS induced by IL-2 from (22.10+/-1.87)U/mg prot to (15.71+/-0.89)U/mg prot. High Ca(2+) (2.5 mmol/L) incubation did not change the inhibitory effect of FAC. Pretreatment with FAC attenuated the increased caffeine-releasable pool of Ca(2+) by IL-2. High K(+) (10 mmol/L) incubation abolished the inhibitory effect of FAC.</p><p><b>CONCLUSION</b>FAC inhibits the vasodilating effect of IL-2 in the isolated aortic ring,which may be mediated by decreasing the activity of NOS. Intracellular calcium release and inward rectifier potassium channel are involved in the inhibitory effect of FAC.</p>

Treatment of interferon-alpha in reducing the endothelium-dependent relaxation of rat thoracic aorta / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To investigate the vascular effect of acute and chronic treatment of interferon-alpha (IFN-alpha) in rat aortic rings.</p><p><b>METHODS</b>Isolated thoracic aortic rings were mounted on the organ bath and the tension of the vessel was recorded.</p><p><b>RESULTS</b>IFN-alpha(10, 100, 1,000 and 10,000 U/ml) caused concentration -dependent relaxation of endothelium-intact aorta rings preconstricted with phenylephrine (PE,10(-6)mol/L), to(90.1+/-0.91)%, (65.1+/-5.21)%, (39.5+/-8.22)% and (35.3+/-8.27)% of pre-drug control, respectively. Removal of the endothelium inhibited the relaxation by IFN-alpha. The vasorelaxant effect of IFN-alpha (100 U/ml ) was attenuated by pretreatment with L-NAME (10(-4)mol/L), methylene blue (10(-5)mol/L) or AMG (10(-4)mol/L), to (97.2+/-5.34)%, (95.1+/-6.25)% and (93.7+/-8.82)% of the control, respectively. Pretreatment with IFN-alpha (1,000,000 U/d, i.p.) for five days markedly inhibited the endothelium-dependent relaxation of the aortic rings to acetylcholine. But the endothelium-dependent relaxation to acetylcholine was not changed by pretreatment of IFN-alpha (10,000 U/ml) with the isolated aorta rings for 2 h.</p><p><b>CONCLUSION</b>The vasorelaxation induced by IFN-alpha in rat aorta rings is endothelium-dependent and is possibly mediated by inducible nitric oxide synthase. Chronic treatment of IFN-alpha may impair the endothelium or NO-sGC pathway.</p>

NO/cGMP signal pathway involved in the disturbance of calcium homeostasis in vascular smooth muscle during the late phase of sepsis / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To evaluate the alterations in calcium metabolism of the vascular smooth muscle of rat thoracic aorta in the late phase of sepsis and to investigate the involvement of nitric oxide (NO)/cyclic-GMP(cGMP) signal transduction pathway in the sepsis-induced vascular hyporeactivity.</p><p><b>METHODS</b>Male Sprague-Dawley rats were subjected to sepsis by cecal ligation and puncture (CLP). Eighteen hours post CLP, rat aortic rings were removed for measurement of contractile responses to vasoconstrictors by using organ bath technique.</p><p><b>RESULT</b>In endothelium intact aortic rings from CLP rats, concentration-contraction curves to phenylephrine (PE) and high KCl were significantly decreased when compared with those from control rats. The transient contraction induced by PE in calcium-free Krebs solution and the concentration-dependent contraction to CaCl(2)in KCl-depolarized medium were also markedly reduced. The hyporeactivity to vasoconstrictors was completely reversed by pretreatment either with aminoguanidine (AMG), a selective inducible nitric oxide synthase inhibitor, or with 1H [1,2,4] oxadiazolo[4,3-a] quininoxalin-1-one(ODQ), an inhibitor of NO-sensitive guanylyl cyclase.</p><p><b>CONCLUSION</b>A generalized impairment in calcium handling in vascular smooth muscle,including the calcium influx through the voltage-operated and receptor-operated channels and calcium release from intracellular calcium stores, is involved in vascular hyporeactivity during the late phase of sepsis. The NO/cGMP signal transduction pathway might be involved in this defect in vascular smooth muscle.</p>