Mitochondrial pores modulate the protective effect of acetylcholine on ventricular myocytes during ischemia/reperfusion injury.

In this study, we investigated the cardioprotective effect of acetylcholine (ACh) via modulation of mitochondrial permeability transition pore (MPTP) opening through the mitochondrial ATP-sensitive potassium channel (mitoK(ATP) channel). In isolated ventricular myocytes from male Sprague-Dawley rats, 0.1 micromol/L ACh was administered for 6 min, before 30 min of simulated ischemia and 30 min of reperfusion (I/R). A mitoK(ATP) inhibitor (5-hydroxydecanoate, 5-HD) and an MPTP opener (atractyloside, Atr) were used to analyze the underlying mechanisms. Myocyte contractile function, myocyte viability, lactate dehydrogenase (LDH) release, reactive oxygen species (ROS) and mitochondrial membrane potential were assayed. During reperfusion, the amplitudes of contraction, +/-dL/dt(max), and end-diastolic length of myocytes were decreased, which were markedly improved by pretreatment with ACh. However, such effects of ACh were reversed by 100 micromol/L 5-HD for 20 min before ischemia, or 20 micromol/L Atr for 20 min at the beginning of reperfusion. Pretreatment with ACh markedly reduced I/R-induced cell death, LDH release, ROS signals and mitochondrial membrane potential dissipation, all of which were reversed by 5-HD or Atr. In conclusion, ACh may protect ventricular myocytes from I/R injury by inhibiting MPTP opening and stabilizing the mitochondrial membrane potential through activating the mitoK(ATP) channel.

[Electrophysiological effect of atorvastatin on isolated rat hearts injured by ischemia/reperfusion].

OBJECTIVE: To investigate the myocardial electrophysiological effect and its underlying mechanisms of atorvastatin (Ator) on isolated rat hearts injured by ischemia/reperfusion (I/R). METHODS: Isolated SD rat hearts were mounted on Langendorff system, and a local I/R was induced by ligation (30 min) and release (15 min) of the left anterior descending artery. During the reperfusion period, the effect of Ator on diastolic excitation threshold (DET), effective refractory period (ERP) and ventricular fibrillation threshold (VFT) on rat heart were measured. RESULT: Compared with the control group, medium concentration of Ator prolonged the ERP in normal rat hearts; low, medium and high concentration of Ator significantly inhibited the decrease of DET, ERP and VFT induced by I/R. However, pretreatment with L-NAME cancelled these cardiac electrophysiological effects of Ator. CONCLUSION: Ator reduced electrophysiological alteration induced by I/R in isolated rat hearts, which may be mediated by activating nitric oxide pathway to enhance the myocardial electrophysiological stability.

[Partial endothelium-dependent vasorelaxation of crocetin and its mechanism].

OBJECTIVE: To investigate the vasorelaxation effect of crocetin (CCT) and its mechanism. METHODS: Isolated aortic rings from Sprague-Dawley rats were mounted in the organ bath system. The tension of the aorta was recorded. RESULT: CCT significantly provoked concentration-dependent relaxation in both endothelium-intact and-denuded aortic rings pre-constricted by phenylephrine (10⁻5 mol/L), and the vasorelaxation in endothelium-intact aortic rings was stronger than that in endothelium-denuded ones. CCT had no significant effects on aortic rings pre-constricted with KCl (6 × 10⁻² mol/L). Pretreatment with eith L-NAME (10⁻4 mol/L), an inhibitor of nitric oxide synthase (NOS), or indomethacin (10⁻5 mol/L), an inhibitor of cyclooxygenase, for 30 min significantly attenuated the relaxation of endothelium-intact aortic rings induced by CCT. Besides, both tetraethylammonium (a Ca²(+)-activated K(+) channel inhibitor, 5 × 10⁻³ mol/L) and 4-aminopyridine (a voltage-sensitive K(+) channel inhibitor, 10⁻³ mol/L), but not the ATP-sensitive K(+) channel inhibitor glibenclamide (3 × 10⁻6 mol/L), significantly attenuated CCT-induced relaxation in endothelium-denuded aortic rings. CONCLUSION: CCT had partial endothelium-dependent relaxation in rat aortas, which may be mediated by activating the endothelial NOS-NO and cyclooxygenase-prostacyclin pathways. The endothelium-independent relaxation in rat aortas induced by CCT may be mediated by Ca²(+)-activated K(+) channels and voltage-sensitive K(+) channels.

[Antiarrhythmic effect of ethyl acetate extract from Chrysanthemum Morifolium Ramat on rats].

OBJECTIVE: To investigate the effect of ethyl acetate extract from Chrysanthemum Morifolium Ramat (CME) on experimental arrhythmia induced by ischemia/reperfusion or aconitine in rats and to explore its underlying mechanisms. METHODS: Arrhythmia model in intact rat was induced by aconitine (30 microg/kg body weight, i.v.). In isolated Langendorff perfused rat hearts, regional ischemia and reperfusion was induced by ligation and release of left anterior descending artery. The ventricular fibrillation threshold (VFT), effective refractory period (ERP), and diastolic excitation threshold (DET) in the isolated heart were measured. The action potentials of papillary muscle in rat right ventricle were recorded by conventional glass microelectrode technique. RESULTS: Compared with control group CME significantly decreased the number and duration of ventricular tachycardia (VT); delayed the occurrence of ventricular premature beats (VPB) and VT induced by aconitine. Arrhythmia score of the CME group was lower than that in aconitine-treated group. CME markedly prolonged the ERP and increased the VFT in the isolated perfused rat hearts during ischemia and reperfusion. CME prolonged action potential duration at 50% and 90% repolarization of the right ventricular papillary muscles and decreased the maximal rate of rise of the action potential upstroke, but did not affect the resting potential, amplitude of action potential. CONCLUSION: CME can reduce myocardial vulnerability and exerts its antiarrhythmic effects induced by aconitine or ischemia/reperfusion, which may be related to its prolongation of action potential duration and effective refractory period that enhance the electrophysiological stability of myocardiaium.

Ischemic postconditioning protects against global cerebral ischemia/reperfusion-induced injury in rats.

BACKGROUND AND PURPOSE: Ischemic postconditioning has been found to decrease brain infarct area and spinal cord ischemic injury. In this study, we tested the hypothesis that ischemic postconditioning reduces global cerebral ischemia/reperfusion-induced structural and functional injury in rats. METHODS: Ten-minute global ischemia was induced by 4-vessel occlusion in male Sprague-Dawley rats. The animals underwent postconditioning consisting of 3 cycles of 15-second/15-second (Post-15/15), 30-second/30-second (Post-30/30), or 60-second/15-second (Post-60/15) reperfusion/reocclusion or 15-second/15-second reperfusion/reocclusion applied after a 45-second reperfusion (Post-45-15/15). RESULTS: Ten minutes of ischemia and 7 days of reperfusion destroyed 85.8% of CA1 hippocampal neurons and 64.1% of parietal cortical neurons. Three cycles of Post-15/15, Post-30/30, and Post-45-15/15 reperfusion/reocclusion markedly reduced neuronal loss after 7 days or 3 weeks of reperfusion and diminished the deficiency in spatial learning and memory. After reperfusion, a period of hyperperfusion followed by hypoperfusion was observed, both of which were blocked by postconditioning. The cytosolic level of cytochrome c increased significantly after 48 hours of reperfusion, and this was inhibited by Post-15/15, Post-30/30, and Post-45-15/15. However, 3 cycles of 60-second/15-second reperfusion/reocclusion failed to protect against neuronal damage, behavioral deficit, or cytochrome c translocation. CONCLUSIONS: Our data provide the first evidence that an appropriate ischemic postconditioning strategy has neuroprotective effects against global cerebral ischemia/reperfusion injury and a consequent behavioral deficit and that these protective effects are associated with its ability to improve disturbed cerebral blood flow and prevent cytochrome c translocation.

Inhibition of superoxide anion-mediated impairment of endothelium by treatment with luteolin and apigenin in rat mesenteric artery.

This study was designed (i) to test the hypothesis that the endothelium-derived hyperpolarizing factor (EDHF) component of ACh-induced vasorelaxation and hyperpolarization of smooth muscle cells (SMCs) are impaired following exposure to superoxide anion, and (ii) to further investigate whether luteolin and apigenin induce vasoprotection at the vasoactive concentrations in rat mesenteric artery. Rat mesenteric arterial rings were isolated for isometric force recording and electrophysiological studies. Perfusion pressure of mesenteric arterial bed was measured and visualization of superoxide production was detected with fluorescent dye. 300 microM pyrogallol significantly decreased the relaxation and hyperpolarization to ACh. Luteolin and apigenin both induced vasoprotection against loss of the EDHF component of ACh-induced relaxation and attenuated the impairment of hyperpolarization to ACh. Oxidative fluorescent microtopography showed that either luteolin or apigenin significantly reduced the superoxide levels. The results suggest that superoxide anion impairs ACh-induced relaxation and hyperpolarization of SMC in resistance arteries through the impairment of EDHF mediated responses. Luteolin and apigenin protect resistance arteries from injury, implying that they may be effective in therapy for vascular diseases associated with oxidative stress.

Opening the calcium-activated potassium channel participates in the cardioprotective effect of puerarin.

The aim of the present study was to determine whether the effective cardioprotection conferred by puerarin against ischemia and reperfusion is mediated by the calcium-activated potassium channel. Hearts isolated from male Sprague-Dawley rats were perfused on a Langendorff apparatus and subjected to 30 min of global ischemia followed by 120 min of reperfusion. The production of formazan, which provides an index of myocardial viability, was measured by absorbance at 550 nm, and the level of lactate dehydrogenase (LDH) in the coronary effluent was determined. Pretreatment with puerarin at 0.24 mmol/l for 5 min before ischemia increased myocardial formazan content and reduced LDH release during reperfusion. Administration of paxilline (1 micromol/l), an antagonist of the calcium-activated potassium channel, attenuated the protective effects of puerarin. In isolated ventricular myocytes, pretreatment with puerarin prevented simulated ischemia and reperfusion injury, hydrogen peroxide-induced cell death and the release of reactive oxygen species. Paxilline and chelerythrine (a protein kinase C inhibitor) both attenuated the effects of puerarin. These findings indicate that puerarin protects the myocardium against ischemia and reperfusion injury via opening the calcium-activated potassium channel and activating protein kinase C.

[Cardioprotection of mitoSlo1 channel activation involves mitochondrial permeability transition in ischemia and reperfusion of rat hearts].

OBJECTIVE: To investigate whether the cardioprotection of mitochondrial Slo channel (mitoSlo(1) channel) is associated with mitochondrial permeability transition in isolated rat hearts subjected to ischemia and reperfusion. METHODS: Isolated perfused rat hearts were subjected to 30 min regional ischemia (occlusion of left anterior descending artery) and 120 min reperfusion. The infarct size, lactate dehydrogenase (LDH) release during reperfusion and ventricular hemodynamic parameters were measured. RESULTS: Pretreatment with mitoSlo(1) channel opener, NS1619 10 micromol/L for 10 min reduced the infarct size and LDH release, and improved the recovery of left ventricular developed pressure, left ventricular end-diastolic pressure, maximal rise/fall rate of left ventricular pressure and coronary flow during reperfusion. Administration of atractyloside (20 micromol/L), an opener of mitochondrial permeability transition pore, for 20 min (last 5 min of ischemia and first 15 min of reperfusion) attenuated the reduction of infarct size and LDH release and improvement of left ventricular performance induced by NS1619. In the isolated mitochondria, a significant inhibition of Ca(2+)-induced swelling was observed when mitochondria were incubated with NS1619. CONCLUSION: MitoSlo(1) channel activation by NS1619 protects the myocardium against ischemia and reperfusion injury by inhibiting mitochondrial permeability transition pore opening.

[Interleukin-2 induced endothelium-dependent relaxation of rat thoracic aorta].

Interleukin-2 (IL-2) therapy often results in potentially life-threatening side effects including hypotension. However, the mechanism has not been completely elucidated. In order to determine whether IL-2 modifies vascular tone, we investigated the effect of IL-2 on rat thoracic aorta rings and the underlying mechanisms. Effects of IL-2 on the contraction of high KCl and phenylephrine (PE) preconstricted rat thoracic aorta with or without endothelium were determined by organ bath technique. To explore the mechanism, nitric oxide synthase inhibitor L-N(G)-nitroarginine methyl ester (L-NAME), guanylyl cyclase inhibitor methylene blue, and cyclooxygenase inhibitor indomethacin were used. IL-2 (10-1000 U/ml) caused concentration-dependent relaxation of aorta rings preconstricted with PE (10 micromol/L) in endothelium-intact rings, but had no effect on KCl (120 mmol/L) preconstricted rings. Removal of the endothelium, or pretreatment with L-NAME (0.1 mmol/L) or methylene blue (10 micromol/L) or indomethacin (10 micromol/L), inhibited the relaxation of IL-2. The results indicate that the relaxation by IL-2 in rat aorta ring is endothelium-dependent and is possibly mediated by the NO-guanylyl cyclase pathway and cyclooxygenase-dependent pathway.

[Effect of interleukin-2 on the activity of Ca2+ ATPase and Na+/K+ ATPase of sarcoplasmic reticulum and sarcolemma].

The purpose of the present study was to investigate whether interleukin-2 (IL-2) changes the activity of sarcoplasmic reticulum (SR) Ca(2+) ATPase, sarcolemmal Ca(2+)ATPase and Na(+)/K(+) ATPase by measuring the Pi liberated from ATP hydrolysis with colorimetrical methods. It was shown that the activity of Ca(2+)ATPase in SR from IL-2-perfused (10, 40, 200, 800 U/ml) rat heart increased dose-dependently. After incubation of the SR with ATP (0.1 approximately 4 mmol/L), the activity of SR Ca(2+)ATPase increased dose-dependently in the control group. In the SR from 200 U/ml IL-2-perfused hearts, the activity of Ca(2+)ATPase was much higher than that in the control group. On the other hand, incubation of the SR with Ca(2+) (1 approximately 40 micromol/L) increased the activity of SR Ca(2+) ATPase in the control group. The activity of SR Ca(2+)ATPase of IL-2-perfused hearts was inhibited as the function to Ca(2+). Pretreatment with specific kappa-opioid receptor antagonist nor-BNI (10 nmol/L) for 5 min attenuated the effect of IL-2 (200 U/ml) on the activity of SR Ca(2+) ATPase. After pretreatment with pertussis toxin (PTX, 5 mg/L) or U73122 (5 micromol/L), IL-2 failed to increase SR Ca(2+)ATPase activity. The activity of SR Ca(2+)ATPase was not changed by incubation of SR isolated from normal hearts with IL-2. Perfusion of rat heart with IL-2 did not affect the activity of sarcolemmal Ca(2+)ATPase and Na(+)/K(+)ATPase. It is concluded that perfusion of rat heart with IL-2 increases the activity of SR Ca(2+)ATPase dose-dependently, which is mainly mediated by cardiac kappa-opioid receptor pathway including a PTX sensitive Gi-protein and phospholipase C. IL-2 increases the activity of SR Ca(2+)ATPase as the function to ATP, but inhibits the activity of SR Ca(2+)ATPase as the function to Ca(2+). IL-2 has no effect on the activity of sarcolemmal Ca(2+)ATPase and Na(+)/K(+)ATPase.

[Role of interleukin-2 in the functional myocardial impairment induced by anoxia and reoxygenation].

OBJECTIVE: To investigate the effect of interleukin-2 (IL-2) on myocardial impairment during ischemia/reperfusion or anoxia/reoxygenation. METHODS: Chemical anoxia was introduced in the isolated rat ventricular myocytes by Krebs-Henseleit (K-H) solution containing 10(-3) mol/L sodium dithionite. The video-tracking system and spectrofluorometric method were employed to verify the cell contraction and calcium homeostasis of the single myocyte. Radioimmunoassay was used to analyze the IL-2 levels in myocardium. RESULTS: The levels of IL-2 in myocardium subjected to ischemia/reperfusion were elevated [(14.34+/-5.99 compared with 22.25+/-3.68)ng/g, P<0.01]. During anoxia, cell contraction and the amplitude of electrically induced calcium transient were depressed and the parameters did not return to the pre-anoxia level during reoxygenation. IL-2 at 200 U/L administered during anoxia aggravated the effect of reoxygenation on cell contraction and calcium transient. After perfusion with IL-2, the malondialdehyde content of myocardial mitochondria was elevated. CONCLUSION: Coexistence of IL-2 during anoxia aggravates the effect of reoxygenation on the cell contraction and calcium homeostasis in the isolated rat ventricular myocytes, in which the mitochondrial lipid peroxidation induced by IL-2 is involved.

[Effects of total flavones of Elsholtzia splendens in isolated ischemia/reperfusion rat hearts].

OBJECTIVE: To investigate the influence of total flavonoids of Elsholtzia splendens (TFES) on isolated ischemia/reperfusion rat hearts and its underlying mechanisms. METHODS: Hearts isolated from male SD rats were perfused on the Langendorff apparatus and subjected to global ischemia for 30 min followed by 120 min of reperfusion. The cardiac infarct size was measured by TTC staining. Hemodynamic parameters and the level of lactate dehydrogenase (LDH) in the coronary effluent were measured. Absorbance at 520 nm was determined in isolated cardiac mitochondria exposed to 200 micromol/L CaCl2 to detect the opening of the mitochondrial permeability transition pore. RESULTS: Pretreatment with TFES (1, 10, 100 microg/ml) for 5 min decreased infarct size and LDH release and improved the recovery of the left ventricular developed pressure. In mitochondria, the decrease of absorbance at 520 nm evoked by CaCl2 was greatly inhibited by TFES. CONCLUSION: TFES prevents myocardial ischemia/reperfusion injury, and this cardioprotective effect is probably via inhibiting mitochondrial permeability transition pore opening.

Endothelium-dependent and -independent vasorelaxant actions and mechanisms induced by total flavonoids of Elsholtzia splendens in rat aortas.

Elsholtzia splendens (ES) is, rich in flavonoids, used to repair copper contaminated soil in China, which has been reported to benefit cardiovascular systems as folk medicine. However, few direct evidences have been found to clarify the vasorelaxation effect of total flavonoids of ES (TFES). The vasoactive effect of TFES and its underlying mechanisms in rat thoracic aortas were investigated using the organ bath system. TFES (5-200mg/L) caused a concentration-dependent vasorelaxation in endothelium-intact rings, which was not abolished but significantly reduced by the removal of endothelium. The nitric oxide synthase (NOS) inhibitor N(ω)-nitro-l-arginine methyl ester (100µM) and the guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,2-α]quinoxalin-1-one (30µM) significantly blocked the endothelium-dependent vasorelaxation of TFES. Meanwhile, NOS activity in endothelium-intact aortas was concentration-dependently elevated by TFES. However, indomethacin (10µM) did not affect TFES-induced vasorelaxation. Endothelium-independent vasorelaxation of TFES was significantly attenuated by KATP channel blocker glibenclamide. The accumulative Ca(2+)-induced contraction in endothelium-denuded aortic rings primed with KCl or phenylephrine was markedly weakened by TFES. These results revealed that the NOS/NO/cGMP pathway is likely involved in the endothelium-dependent vasorelaxation induced by TFES, while activating KATP channel, inhibiting intracellular Ca(2+) release, blocking Ca(2+) channels and decreasing Ca(2+) influx into vascular smooth muscle cells might contribute to the endothelium-independent vasorelaxation conferred by TFES.

[Luteolin reduces cardiac dysfunctions in streptozotocin-induced diabetic rats].

OBJECTIVE: To investigate the effects of luteolin (Chinese Traditional Medicine) on cardiac functions and mitochondrial oxidative stress in streptozotocin (STZ)-induced diabetic rats. METHODS: Male SD rats were randomly divided into a normal control group, a luteolin control group, a diabetic group, and diabetic groups orally administered with a low dose (10 mg/(kg x d)) or a high dose of luteolin (100 mg/ (kg x d)) for eight weeks. The body weight, blood glucose, cardiac functions, left ventricular weight, myocardial collagen and reactive oxygen species (ROS) levels were assayed. The cardiac mitochondrial ROS level, superoxide dismutase (SOD) activity and the mitochondrial swelling were measured. RESULTS: Treatment with luteolin had no effect on the blood glucose but reduced the losing of body weight in diabetic rats. High dose of luteolin markedly reduced the ratio of ventricular weight and body weight, increased the left ventricular develop pressure, and decreased the left ventricular end diastolic pressure in diabetic rats. The myocardial levels of ROS and collagen, the cardiac mitochondrial ROS level, and the mitochondrial swelling in diabetic rats were all markedly reduced by high dose of luteolin. Furthermore, high dose of luteolin significantly increased the mitochondrial SOD activity in diabetic rat hearts. CONCLUSION: Treatment with luteolin for 8 weeks markedly improves the cardiac function, which may be related to reducing mitochondrial oxidative stress and mitochondrial swelling in diabetic rats.

[Effect of S-allyl-L-cysteine on isolate heart subject to ischemia/reperfusion].

OBJECTIVE: To investigate the effect of S-allyl-L-cysteine (SAC) on isolated rat heart subject to ischemia/reperfusion(I/R) injury and the mechanisms. METHODS: The isolated perfused rat hearts on a Langendorff apparatus were subjected to global ischemia for 30 min and followed by 120 min of reperfusion. Hemodynamic index, the production of formazan and the level of lactate dehydrogenase (LDH) in the coronary effluent were determined. Superoxide dismutase (SOD) and reactive oxygen species (ROS) in myocardial homogenates were measured. RESULTS: Compared with I/R group, the hemodynamics were greatly improved, the production of formazan was increased, and LDH level in effluent was reduced in SAC group. SAC improved the SOD activity and significantly decreased the level of ROS. In addition, threonine (Thr) attenuated the protective effect of SAC significantly. CONCLUSION: SAC has protective effect against myocardial ischemia/reperfusion injury on rats. The possible mechanism is that SAC be transported into the cell through alanine-serine-cysteine-transporter 1 (ASCT-1) improves SOD activity and reduces the level of ROS.

[Expression and function of autophagy after ischemia/reperfusion in rats hippocampus neuron].

OBJECTIVE: To explore the expression of autophagy after ischemia/reperfusion and its possible function in rats hippocampus neurons. METHODS: After 2 hours oxygen-glucose deprivation and different periods time of reperfusion (OGD/R) treatment in primary hippocampal neurons, neuron viability was evaluated by MTT assay, specific structure of autophagosome and specific protein of autophagy microtubule-associated protein 1 light chain 3 B (LC3B) were detected by transmission electron microscope and immunofluorescence respectively. The inhibitor of autophagy 3-Methyladenine (3-MA) was also used to exam the viability of neurons. RESULTS: Treatment by OGD/R markedly reduced neuronal viability. Compared to the control group, autophagy existed in different time periods after OGD/R shown both in transmission electron microscope and immunofluorescence. Application of 3-MA significantly reduced neuronal viability. CONCLUSION: Oxygen-glucose deprivation can activate autophagy in rat hippocampus neurons, which may resist the injury during ischemia/reperfusion.

[Auricularia auricular polysaccharide protects myocardium against ischemia/reperfusion injury].

OBJECTIVE: To determine whether auricularia auricular polysaccharide (AAP) protects heart against ischemia/reperfusion (1/ R) injury and its underlying mechanisms. METHODS: Male Sprague-Dawley rats, pretreated with AAP (50, 100, 200 mg/(kg x d), gastric perfusion) for 4 weeks, were used for Langendorff isolated heart perfusion. The hearts were subjected to global ischemia for 30 min followed by 120 min of reperfusion and the left ventricular hemodynamic parameters were measured. Formazan, a product of 2, 3, 5-triphenyl-tetrazolium chloride (TTC), which is proportional to myocardial viability, was measured at 490 nm, and the level of lactate dehydrogenase (LDH) in the coronary effluent was measured to evaluate the cardiac injury. The cardiac malondialdehyde (MDA), a product of lipid peroxidation, and superoxide dismutase (SOD) activity were determined after myocardial I/R. RESULTS: The pretreatment with AAP at 50, 100, 200/(kg d) for 4 weeks before I/R increased myocardial formazan content, reduced LDH release, improved the recovery of the left ventficular developed pressure, maximal rise rate of left ventricular pressure, and rate pressure product (left ventricular developed pressure multiplied by heart rate) attenuated the decrease of coronary flow during reperfusion. The cardiac protective effect of high dose AAP was more potent than that of compound radix salviae miltiorrhizae (CRSM, 4 ml/(kg x d), gastric perfusion for 4 weeks). Pretreatment with AAP (100 mg/(kg x d)) markedly inhibited the increase of MDA level and the decrease of SOD activity induced by I/R in myocardium. CONCLUSION: The findings indicate that in the isolated rat heart, AAP protects myocardium against ischemia/reperfusion injury via enhancing the activity of SOD and reducing lipid peroxidation in heart.

[Myocardial protective effect of acetylcholine against ischemia/reperfusion injury and its underlying mechanism].

OBJECTIVE: To determine whether the caidioprotection of acetylcholine (ACh) against ischeniia/reperftision (I/R) injury is re-kited to mitochondrial permeability transition pore (MEW) and mitochondrial AW-sensitive potassium channel (mitoK(ATP)). METHODS: Male Sprague-Dawley rats were used for Langendorif isolated bean perkision. The hearts were subjected to global ischemia for 30 mm followed by 120 rein of reperfusion and the left ventricular hemodynaniic parameters were measured. Formazan, a product of 2,3, 5-triphenyl-tetrazolium chloride (TTC), which is proportional to myocardial viability, was measured at 490 nm, and the level of lactate dehydrogenase (LDH) in the coronary effluent was measured to evaluate the cardiac injury. RESULTS: The pretreatment with ACh (0.1 mol/L, 5 mm) before I/R markedly increased myocardial formazan content, reduced LDH release, improved the recovery of the left veritficular developed pressure, +/- dP/dtmax, and rate pressure product (left ventricular developed pressure multiplied by hean rate) and attenuated the decrease of coronary flow during reperfusion. The opener of MPTP, atiractyloside (20 mmoL/L) or the inhibitor of mitoK(ATP), 5-hydroxydecanoate (100 micromol/L) abolisbed the beneficial effect of ACh. CONCLUSION: In the isolated rat bean, ACh protects myocardium against ischemia/reperfusion injury via inhibiting the opening of MPTP and increasing the opening of mitoKATP in heart.

[Study of the effects of Auricularia auricular polysaccharide on local ischemia/reperfusion injury in rat].

OBJECTIVE: To investigate the influence of Auricularia Auricular polysaccharide (APP) on acute cerebral injury induced by ischemia/reperfusion in rats and its underlying mechanism. METHODS: Adult male SD rats were intragastrically pretreated with AAP at a low (50 mg/kg) or high (100 mg/kg) dose once a day for 20 days before operation. Rats intraperitoneally injected with ginkgo biloba extract (EGb671) were taken as positive control. Focal ischemia was achieved by middle cerebral artery occlusion (MCAO) on the right side for 60 min. After 24 hrs of reperfusion, the nerve function defects were recorded by Longa's score and the brain infarct sizes were measured by 2,3,5-Triphenyl-tetrazolium-chlor (TTC) staining. Apoptotic neurons were detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining after 48 h of reperfusion. The levels of oxidative stress was determined via the mitochondria-generated reactive oxygen species (ROS). RESULTS: AAP treatment decreased Longa's score, brain infarct size, apoptotic neurons and mitochondria-generated ROS in a dose-dependent manner. AAP at 100 mg/kg gave a better performance compared with EGb671 on all parameters examined. CONCLUSION: AAP treatment protected rat brain from focal ischemia/reperfusion injury by its anti-oxidative effect and worked better than EGb671.

[Effect of gap junction on the cardioprotection of ischemic postconditioning in rat heart].

AIM: To determine whether the cardioprotection of ischemic postconditioning and heptanol in ischemic heart against ischemia/reperfusion (I/R) is mediated by gap junction. METHODS: The effect of ischemic postconditioning, heptanol at different doses (0.03, 0.06, 0.30, and 0.60 mg/kg) and AAP10 (10 mg/kg) on the intact rat heart during 30 min ischemia and 2 h of reperfusion was observed. Ischemic postconditioning was achieved by 3 cycles of 10 s reperfusion/10 s regional ischemia starting at the beginning of the reperfusion. The infarct size and the arrhythmia scores were measured. The effect of ischemic postconditioning, heptanol at different doses (0.05, 0.10, 0.50 and 1.00 mmol/L) and AAP10 (1 x 10(-7)mol/L) on the isolated heart during 30 min ischemia and 2 h of reperfusion was observed. Ischemic postconditioning was achieved by 6 cycles of 10 s reperfusion/10 s global ischemia starting at the beginning of the reperfusion. The arrhythmia scores and conduction velocity of ventricle muscle were measured. RESULTS: In the intact rat heart model, ischemic postconditioning and heptanol reduced infarct size and arrhythmia scores. In the Langendorff perfused rat heart model, ischemic postconditioning and heptanol reduced arrhythmia scores and conduction velocity of ventricle muscle. Administration of AAP10, an opener of gap junction attenuated the cardioprotection of ischemic postconditioning and heptanol. CONCLUSION: The cardioprotection of ischemic postconditioning and heptanol may be related to the attenuation of gap junction communication on myocardiac ischemia/reperfusion injury.