OBJECTIVETo explore the relationship between α-actinin content and cardiac function in rats during myocardial ischemia-reperfusion.

METHODSThirty-two rats were randomized equally into sham-operated group, 30 min ischemia group, 1 h ischemia group, and 1 h ischemia with 2 h reperfusion group. Acute myocardial ischemia was induced in the 3 ischemia groups by ligation of the left anterior descending coronary artery, and the cardiac functions were evaluated. The myocardial contents of α-actinin was measured by immunohistochemistry, and phospholipase C (PLC) and phosphatidylinositol-3-kinase (PI3K) contents were determined by ELISA after the operations.

RESULTSThe left ventricular systolic pressure (LVSP), +dp/dt max, and -dp/dt max tended to decrease during myocardial ischemia, and increased after reperfusion, and the left ventricular end-diastolic pressure (LVEDP) showed reverse changes. The levels of α-actinin decreased with prolonged ischemia, showing a significant difference in 1 h ischemia group from those in the other 3 groups. PI3K and PLC contents were significantly increased with prolonged myocardial ischemia. Stimulation by LY-294002 and U-73122 caused enhanced contraction of single cardiomyocytes, and also increased the fluorescence intensity of α-actinin in the cardiomyocytes compared with that in 1 h ischemia group.

CONCLUSIONSThe cardiac dysfunction during acute ischemia-reperfusion in rats may be related with the changes of myocardial α-actinin content, which are probably a result of increased PI3K and PLC contents in the ischemic myocardium.

Actinin ; metabolism ; Animals ; Myocardial Ischemia ; metabolism ; physiopathology ; Myocardial Reperfusion Injury ; metabolism ; physiopathology ; Myocardium ; metabolism ; Phosphatidylinositol 3-Kinase ; metabolism ; Rats ; Rats, Wistar ; Type C Phospholipases ; metabolism

OBJECTIVETo investigate the effect of interleukin-2 (IL-2) on myocardial impairment during ischemia/reperfusion or anoxia/reoxygenation.

METHODSChemical 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.

RESULTSThe 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.

CONCLUSIONCoexistence 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.

Animals ; Calcium ; metabolism ; Interleukin-2 ; physiology ; Lipid Peroxidation ; Male ; Malondialdehyde ; blood ; Mitochondria, Heart ; metabolism ; Myocardial Ischemia ; physiopathology ; Myocardial Reperfusion Injury ; physiopathology ; Rats ; Rats, Sprague-Dawley

The effect of acute ischemia on the electrophysiological characteristics of the three layers myocardium of canine in vivo was investigated. Twelve canines were divided into two groups randomly: acute ischemia (AI) group and sham operation (SO) group. By using the monophasic action potential (MAP) technique, MAP and effective refractory period (ERP) of the three layers myocardium were measured by specially designed plunge needle electrodes and the transmural dispersion of repolarization (TDR) and transmural dispersion of ERP (TDE) were analyzed. The results showed that in the AI group, MAP duration (MAPD) was shortened from 201.67 +/- 21.42 ms to 169.50 +/- 13.81 ms (P < 0.05), but ERP prolonged to varying degrees and TDE increased during ischemia. In the SO group, MAPD and ERP did not change almost. Among of the three layers myocardium of canine, MAPD was coincident in two groups. It was concluded that during acute ischemia, MAPD was shortened sharply, but there was no significant difference among of the three layers myocardium. The prolonged ERP was concomitant with increased TDE during acute ischemia, which may play an important role in the occurrence of arrhythmias induced by acute ischemia. These findings may have important implications in arrhythmogenesis.
Action Potentials/*physiology ; Electrodes ; Heart/physiopathology ; Myocardial Ischemia/*physiopathology ; Myocardium/*metabolism ; Random Allocation ; Refractory Period, Electrophysiological/*physiology

AIMTo observe the effect of LPC on the pacemaker current I(f) in ischemic myocardium and if the effect could be reversed by ISO.

METHODSBy using two microelectrode voltage clamp technique to measure and compare the amplitude of I(f) of ischemic myocardium in the presence of LPC and LPC add ISO.

RESULTSIschemia decreased the amplitude of I(f) at all membrane potential levels. Adding LPC 2 x 10(-5) mol/L to the ischemia-like solution, the amplitude of I(f) decreased further (n = 5, P < 0.05), it means that LPC aggravated the inhibitory effect of "ischemia" on the pacemaker activity. Adding LPC 2 x 10(-5) mol/L and ISO 1 x 10(-6) mol/L together to the ischemia-like solution, the amplitude of I(f) increased significantly at membrane potential -90 mV to - 120 mV (n = 8, P < 0.05) compared with ischemia condition, but still did not reach the levels before ischemia.

CONCLUSIONIn acute myocardial ischemia condition, toxic metabolite LPC accentuated its inhibitory effect on pacemaker current I(f), a local release and accumulation of catecholamine could not completely reverse their inhibitory effect.

Animals ; Isoproterenol ; metabolism ; Lysophosphatidylcholines ; pharmacology ; Membrane Potentials ; drug effects ; Microelectrodes ; Myocardial Ischemia ; metabolism ; physiopathology ; Myocardium ; Patch-Clamp Techniques ; Sheep

UNLABELLEDOBJECTIVE To investigate the effect of Guanxinkang (GXK) on ATP-sensitive potassium channel in myocardial cells of rat with ischemic/reperfusion injury and its possible mechanism for cardiac vascular protection and anti-myocardial ischemia.

METHODSWistar rats were established into I/R injured models by 10 min perfusion--30 min no-flow ischemia--45 min reperfusion, and divided into 5 groups: the I/R model group and 4 treatment groups treated respectively with glibenclamide, pinacidil, GXK and GXK+glibenclamide. Rats' heart were isolated for detecting Ca(2+)-Mg(2+)-ATPase, Na(+)-K(+)-ATPase activity in myocardial cells, and the changes of current in ATP-sensive potassium channel (K(ATP)) was recorded by whole patch clamp technique. Data were controlled by those taken from normal rats in a control group.

RESULTSK(ATP) in the GXK treated group were higher than that in the I/R model group; and similar to that in the pinacidil treated group (P > 0.05). As compared with the model group, activities of Ca(2+)-Mg(2+)-ATPase and Na(+)-K(+)-ATPase in the GXK treated group were increased significantly (P < 0.05).

CONCLUSIONGXK shows definite intervention effect on myocardial I/R injury; which is possibly by way of furthering the opening of K(ATP) channel, decreasing Ca2+ influx, and inhibiting Ca2+ overload.

Animals ; Calcium ; metabolism ; Drugs, Chinese Herbal ; pharmacology ; KATP Channels ; drug effects ; Male ; Myocardial Ischemia ; metabolism ; physiopathology ; Myocardial Reperfusion Injury ; prevention & control ; Myocytes, Cardiac ; metabolism ; Rats ; Rats, Wistar

AIMTo investigated the effect of estrogen on global myocardial ischemia/reperfusion (I/R) injury in ovariectomized (Ovx) rats.

METHODSSprague-Dawley rats were randomly repartitioned into three groups including sham-operated(Sham), ovariectomized (Ovx), or ovariectomized and then given 17beta-estradiol (Ovx + E2). Hearts were excised, mounted on the Langendorff. After the initial stabilization period, all of the three group hearts were randomly divided into normal perfusion subgroup (Control) and I/R perfusion subgroups. Control, perfused for 60 min after stabilization. I/R perfusion subgroups divided into 10 min I + 30 min R, 20 min I + 30 min R, 30 min I + 0 min R, 30 min I + 5 min R, 30 min I + 15 min R and 30 min I + 30 min R. And then, every group hearts were isolated into the single cardiomyocyte. The cardiomyocytes basal contraction and isoproterenol(ISO) stimulation contraction were measured. The viability and yield of cardiomyocytes were counted. LDH and CK concentrations in coronary effluent were assayed with assay kit.

RESULTSThe viability and yield of cardiomyocytes were significantly decreased in the conditions of 30 min ischemia followed by different times of reperfusion. The releases of LDH and CK in coronary effluent were significantly increased in the conditions of 30 min ischemia followed by different times of reperfusion. Except the 10 min and 20 min ischemia, the releases of LDH and CK were significantly increased in Ovx during I/R. Ovx + E2 could abate the heart injury through decreasing the releases of LDH and CK. Besides the control and the 10 min I + 30 min R groups, the myocardial basal and ISO stimulation contraction were higher from Ovx than Sham, and the effect was reversed by Ovx + Ez.

CONCLUSIONThe results indicate estrogen plays a cardioprotective role in global myocardial ischemia/reperfusion injury in ovariectomized (Ovx) rats.

Animals ; Estradiol ; pharmacology ; Estrogens ; pharmacology ; Female ; Myocardial Contraction ; physiology ; Myocardial Ischemia ; physiopathology ; Myocardial Reperfusion Injury ; prevention & control ; Myocytes, Cardiac ; metabolism ; physiology ; Ovariectomy ; Random Allocation ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo explore the cardioprotection effect of co-treatment with ischemic postconditioning and preconditioning in ischemia/reperfusion (I/R) injury and the related mechanism.

METHODSMale Sprague-Dawley rats were used for Langendorff isolated heart perfusion. The hearts were subjected to global ischemia for 60 min followed by 120 min of reperfusion. The cardiomyocyte viability was measured by MTT-formazan method, and the cardiac injury was evaluated by the levels of lactate dehydrogenase (LDH) in the coronary effluent. Ventricular hemodynamic parameters were also measured.

RESULTIn 60 min of ischemia and 120 min of reperfusion group, ischemic postconditioning increased formazan content, reduced LDH release, but hemodynamic parameters did not improved. Co-treatment with ischemic postconditioning and preconditioning during the prolonged ischemia further improved the hemodynamic parameters. The calcium activated potassium channel antagonist paxilline attenuated the effect of co-treatment with ischemic postconditioning and preconditioning.

CONCLUSIONIschemic postconditioning and preconditioning may synergically protect myocardium from severe ischemia injury, which may be related to calcium-activated potassium channel.

Animals ; Cell Survival ; In Vitro Techniques ; Ischemic Preconditioning, Myocardial ; methods ; L-Lactate Dehydrogenase ; metabolism ; Male ; Myocardial Ischemia ; pathology ; physiopathology ; Myocardial Reperfusion Injury ; metabolism ; physiopathology ; prevention & control ; Myocardium ; metabolism ; pathology ; Potassium Channels, Calcium-Activated ; metabolism ; Rats ; Rats, Sprague-Dawley

To study the effects of different pH HEPES-KH reperfusate solution on immature myocardial protection, isolated perfused Langendorff model from immature rabbit hearts were developed formed. Control group (C) was perfused only with pH 7.4 HEPES-KH solution for 90 min. Ischemia/reperfusion group (group I/R) was perfused with pH 7.4 HEPES-KH solution before ischemia or after ischemia. Experimental group (group E), after ischemia, was perfused with pH 6.8, pH 7.1 and pH 7.4 HEPES-KH solutions for 5 min, 5 min, and 20 min, respectively. The left ventricular function recovery, MWC, LDH and CK leakage, MDA, ATP content, and SOD activity were determined. Our results showed that the left ventricular function recovery, ATP content and SOD activity in group E were higher than those of group I/R (P < 0.05). MWC, MDA content, LDH and CK leakage in group E were lower than those of group I/R (P < 0.05). These findings suggested that pH paradox might be one of important mechanisms for immature myocardial ischemia-reperfusion injury, and acidic perfusate, at the beginning of reperfusion, might attenuate pH paradox and ameliorate functional recovery in isolated perfused immature rabbit hearts.
Animals ; Cardioplegic Solutions ; pharmacology ; Female ; Heart ; physiopathology ; Heart Arrest, Induced ; Hydrogen-Ion Concentration ; Male ; Myocardial Ischemia ; metabolism ; physiopathology ; Myocardial Reperfusion Injury ; metabolism ; physiopathology ; prevention & control ; Myocardium ; metabolism ; Rabbits ; Random Allocation ; Superoxide Dismutase ; metabolism

OBJECTIVEThe mechanism through which platelet activating factor (PAF) induces cardiac electrical activity and arrhythmia is not well understood and previous studies have suggested a potential involvement of ion channels in its action. The present study was aimed to clarify the role of PAF in fatal arrhythmias following acute myocardia infarction (AMI) and the underlying mechanism.

METHODS(1) Blood PAF levels were measured among 72 AMI patients at the time of diagnosis with AMI and 48 h later, and their electrocardiogram (ECG) was recorded continuously. (2) Ischemia simulation and surface electrocardiogram were conducted in 20 pigs and their PAF levels were measured. (3) PAF perfusion and standard microelectrode recording were performed on guinea pig papillary muscles.

RESULTSIn both humans and pigs, elevated PAF levels were detected in AMI and simulated ischemia, respectively, and even higher PAF levels were found when fatal arrhythmias occurred. In guinea pig myocardium, PAF induced a shortening of action potential duration at 90% level of repolarization (APD90)under non-ischemic conditions and a more pronounced shortening under early simulated ischemic conditions.

CONCLUSIONAMI and ischemia are associated with increased PAF levels in humans and pigs, which are further raised when fatal arrhythmia follows. The effects of PAF on the myocardium may be mediated by multiple ion channels.

Animals ; Arrhythmias, Cardiac ; blood ; etiology ; physiopathology ; Electrocardiography ; Female ; Heart ; physiopathology ; Humans ; Male ; Middle Aged ; Myocardial Ischemia ; blood ; complications ; physiopathology ; Platelet Activating Factor ; metabolism ; Swine

To shed light on cardiac effects of the potent vasoconstrictive peptide urotensin II (U II), Langendorff-perfused isolated rat hearts were consecutively perfused with 0.1, 1 and 10 nmol/L U II, for 5 min at each dose, followed by 5-min washout. Moreover, isolated hearts subjected to 20-min global no-flow ischemia were reperfused with U II (1 or 10 nmol/L) for 20 min. Heart function parameters including heart rate, left ventricular pressure and dP/dt were monitored; content of protein and myoglobin, and activity of lactate dehydrogenase (LDH) in coronary effluent were determined; malondialdehyde (MDA) in myocardium and [(125)I]-U II binding sites in plasma membrane were measured after the completion of perfusion. The results showed that: (1) In normal rat hearts, the coronary flow was decreased and the heart function was suppressed by U II dose-dependently, and these changes were not abolished by washout. The leakage of cardiac protein, myoglobin and LDH increased with the increment of U II, but it diminished rapidly after washout. In contrast, MDA content in U II -treated myocardium was not statistically different from that in normal myocardium. (2) Ischemia-reperfusion caused significant decreases in coronary flow, suppression of heart function, and leakage of protein and LDH. In U II -reperfused hearts, all these disorders were significantly aggravated and myocardial MDA content significantly increased (P<0.01), to a greater extent in the presence of higher dose of U II. (3) The maximal binding capacity (B(max)) of U II receptors in plasma membrane from ischemia-reperfusion myocardium increased significantly as compared with that of normal myocardium (20.53+/-1.98 vs 14.65+/-1.78 fmol/mg pr, P<0.01), while Kd remained unchanged. These results indicate that U II caused injury to the isolated rat hearts under normal perfusion, and worsened the injury of the hearts under ischemia-reperfusion, in which U II receptors were up-regulated.
Animals ; Female ; Heart ; drug effects ; physiopathology ; In Vitro Techniques ; Male ; Myocardial Ischemia ; metabolism ; physiopathology ; Myocardial Reperfusion Injury ; metabolism ; physiopathology ; Myocardium ; metabolism ; pathology ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Urotensins ; pharmacology