Brain Ischemia ; metabolism ; pathology ; prevention & control ; Humans ; Ischemic Preconditioning ; methods ; Myocardial Reperfusion Injury ; metabolism ; pathology ; prevention & control ; Reperfusion Injury ; metabolism ; pathology ; prevention & control

The effect of limb ischemic preconditioning (LIP) on ischemia-reperfused myocardium was examined in the urethane-anesthetized rats to determine whether LIP produces cardioprotection and to observe the roles of adenosine and neural reflex in this effect. The area at risk (AR) and infarct area (IA) were determined using Evans blue and nitro-blue tetrazolium staining respectively. Infarct size (IS) was defined as 100xIA/AR (%). The results obtained are as follows: (1) During 30 min myocardial ischemia and subsequent 120 min reperfusion, the myocardial infarct size occupied 51.48+/-0.82% of the area at risk. (2) LIP significantly reduced the myocardial infarct size to 35.14+/-0.88% (p<0.01 ), indicating the cardioprotective effect of such an intervention. (3) Femoral nerve section (FNS) completely abolished the cardioprotection afforded by LIP. (4) Intrafemoral artery injection of adenosine (10 nmol/kg) produced a similar effect to that of LIP, reducing the myocardial infarct size to 37.28+/-1.68%, while intrafemoral vein injection of the same dose of adenosine showed no effect. (5) Pretreatment with a selective adenosine A(1) receptor antagonist 8-cyclopentyl-1,diproylxanthine (DPCPX ) (32 nmol/kg) partially abolished the cardioprotection of LIP on myocardium. Taken together, it is concluded that LIP reduces infarct size following myocardial ischemia-reperfusion, and that the locally released adenosine and thereby the activated relevant neural pathway play an important role in the cardioprotection provided by LIP.
Adenosine ; metabolism ; Animals ; Extremities ; blood supply ; Ischemic Preconditioning ; Male ; Myocardial Infarction ; pathology ; prevention & control ; Myocardial Reperfusion Injury ; pathology ; prevention & control ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo investigate the effects of hydrogen sulfide preconditioning on myocardial ischemia reperfusion injury in rats.

METHODSSprague-Dawley male rats were divided into 4 groups with 10 in each group: in S group rats received sham operation; in IR group rats were given with NS (1.0 ml/kg iv) 24 h before ischemia; in H group rats were treated with NaHS (0.05 mg/kg iv) 24 h before ischemia; and in D group, NaHS-treated rats received 5-hydroxydecanoate (5-HD) 15 min before ischemia. Rats in IR group,H group and D group were subjected to ischemia by occlusion of coronary artery for 30 min followed by 2 h of reperfusion. At the end of the reperfusion,myocardial infarct size was measured. SAM-s was measured by Western blotting. Plasma SOD activity and MDA were determined at the end of reperfusion.

RESULTSThe infarct size was significantly lesser in H group (25.40 % ± 3.54%) than that in IR group (38.27% ±5.64%,P<0.05). The SAM-s protein expression in myocardium was significantly lower in H group than that in IR group. The plasma MDA content was significantly lower and SOD activity was higher in H group than those in IR group,but there was no difference between IR group and D group.

CONCLUSIONThe hydrogen sulfide preconditioning attenuates myocardial IR injury possibly through down-regulating SAM-s expression,reducing the production of oxygen free radicals and enhancing anti-oxidize effect in rats.

Animals ; Disease Models, Animal ; Hydrogen Sulfide ; pharmacology ; Ischemic Preconditioning, Myocardial ; Male ; Myocardial Reperfusion Injury ; metabolism ; pathology ; prevention & control ; Myocardium ; metabolism ; pathology ; Rats ; Rats, Sprague-Dawley

The effects of femoral nerve electrostimulation (FNES) on ischemia-reperfused myocardium were examined in the urethane- anesthetized rats to determine whether FNES may provide cardioprotection and to observe the possible mechanism. The area at risk (AR) and infarct area (IA) were determined using Evans blue and nitro-blue tetrazolium staining, respectively. Infarct size (IS) was defined as 100xIA/AR (%). The results are as follows: (1) During 30 min myocardial ischemia and subsequent 120 min reperfusion, the myocardial infarct size occupied (54.96+/-0.82)% of the area at risk. (2) FNES of high frequency (10 V, 100 Hz, 1 ms) significantly reduced myocardial infarct size to (36.94+/-1.34)% (P<0.01), indicating the cardioprotective effect FNES of high frequency on myocardial ischemia-reperfusion, while FNES of low frequency (10 V, 10 Hz, 1 ms) had no effect on myocardial infarct size. (3) Pretreatment with either naloxone (5 mg /kg, i.v), a nonselective opioid receptor antagonist, or glibenclamide (5 mg /kg, i.v), a K(ATP) channel antagonist, completely abolished the cardioprotection of FNES (100 Hz) from myocardial ischemia-reperfusion. It is suggested that FNES of high frequency can protect myocardium from ischemia-reperfusion injury. The possible mechanism is that FNES of high frequency may induce the release of opioids from the central nervous system, and the activation of opioid receptors in the heart results in an opening of myocardial K(ATP) channels which can protect myocardium.
Animals ; Electric Stimulation ; methods ; Femoral Nerve ; physiopathology ; Glyburide ; pharmacology ; Male ; Myocardial Infarction ; pathology ; Myocardial Reperfusion Injury ; pathology ; prevention & control ; Naloxone ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Receptors, Opioid ; metabolism

OBJECTIVEIn this study, we try to find the better protocol of limb ischemia postconditioning by observing different protective effects of limb ischemic postconditioning (different strength and time windows in rabbits).

METHODS42 healthy New Zealand rabbits were randomly divided into 7 groups (n = 6): Sham; Control (CON); Skeletal muscle postconditioning (SP); 6 min-delayed skeletal muscle postconditioning (6M-DSP); 1 min-delayed skeletal muscle postconditioning (1M-DSP); Strengthen skeletal muscle postconditioning (SSP); Weakened skeletal muscle postconditioning (WSP). Acute ischemia/reperfusion (I/R) model was induced by 45 minutes occlusion on left circumflex coronary artery (LCX) and 2 hours reperfusion in all anesthetized open-chest rabbits except the Sham. Limb ischemia was induced by external iliac arteries occlusion and reperfusion through artery clamps. The extent of myocardial infarction was assessed by triphenyltetrazolium (TTC) staining. Blood serum creatine kinase (CK) activity and lactate dehydrogenase (LDH) activity were measured at baseline,the end of ischemia, after 1 hour and 2 hours of reperfusion respectively.

RESULTSCompared with the CON, the weight ratio and area ratio of myocardial infarction size were significantly decreased by 49.97% and 43.78% in SP, by 42.32% and 42.68% in 1M-DSP, by 48.36% and 48.86% in SSP (P < 0.05). But there was no significant difference between SP and 1M-DSP and SSP (P > 0.05). Otherwise, compared with the CON, myocardial infarct size was not significantly reduced in 6M-DSP or WSP (P > 0.05). The change of CK was similar to the trend of myocardial infarct size.

CONCLUSIONThe limb ischemia strength of 5 mini/1 minR x 1 cycle could significantly reduce the myocardial ischemia/ reperfusion injury in rabbits, if it was achieved before myocardial reperfusion.

Animals ; Extremities ; blood supply ; Ischemic Postconditioning ; methods ; Male ; Muscle, Skeletal ; blood supply ; Myocardial Infarction ; pathology ; Myocardial Reperfusion Injury ; pathology ; prevention & control ; Myocardium ; metabolism ; Rabbits

OBJECTIVE: To investigate whether morphine preconditioning has the delayed protective effect on rabbit myocardium. METHODS: Thirty New Zealand white rabbits were randomly divided into a NS group, a Mor-12 group and a Mor-24 group (n=10). In the Mor-12 group and Mor-24 group, morphine (3 mg/kg) was infused into rabbits, while the same volume of normal saline (NS) was given to rabbits in the NS group. Twelve hours after morphine infusion in the Mor-12 group, 24 h after NS or morphine infusion in the NS group and Mor-24 group, rabbits were subjected to 30 min left anterior descending coronary artery occlusions and were reperfused for 120 min. In 8 of the 10 rabbits in each group, arterial blood samples were taken before the ischemia (T1), 30 min after the ischemia (T2) and 120 min after the reperfusion (T3) to determine the concentration of cardiac troponin I (cTnI), and the myocardial infarct area was determined at the end of reperfusion. In the other 2 of the 10 rabbits in each group,the cell ultramicro-structure injury of myocardium was examined by electron microscope at the end of reperfusion. RESULTS: The concentration of cTnI at T2 and T3 in the Mor-24 group was lower than that in the NS group and Mor-12 group.The myocardial infarct size, and cell ultramicrostructure injury of myocardium in the Mor-24 group were decreased compared with the NS group and Mor-12 group. CONCLUSION Morphine preconditioning has delayed protective effect on rabbit myocardium.
Animals ; Ischemic Preconditioning, Myocardial ; methods ; Morphine ; pharmacology ; Myocardial Reperfusion Injury ; pathology ; prevention & control ; Myocardium ; metabolism ; ultrastructure ; Rabbits ; Random Allocation ; Time Factors ; Troponin I ; blood

The aim of the present studies was to investigate the cardioprotection of late IP at 72 h and determine the involvement of iNOS, nNOS and COX-2 in this protection. Conscious rabbits were preconditioned with three cycles of 5-minute coronary occlusion/5-minute reperfusion. The myocardial infarct area in the rabbits preconditioned 72 h earlier was significantly smaller than that in control rabbits. The activity of lactate dehydrogenase (LDH) and the level of 6-Keto-PGF1alpha in the rabbits preconditioned 72 h earlier were lower than those in control rabbits. The left ventricular systolic pressure (LVSP) and maximal velocity of contraction and relaxation (+/- dP/dtmax) were improved in rabbits preconditioned 72 h earlier. The nNOS-selective inhibitors N-propyl-L-arginine and selective cyclooxygenase-2 (COX-2) inhibitor celecoxib completely blocked the protection of late IP at 72 h, whereas the iNOS selective inhibitor S-methybisothiourea had no effect. In conclusion, the cardioprotection observed in the final stage of late IP (72 hours) is mediated by nNOS or COX-2, but not by iNOS.
Animals ; Cyclooxygenase 2 ; metabolism ; physiology ; Ischemic Preconditioning, Myocardial ; Male ; Myocardial Infarction ; enzymology ; pathology ; prevention & control ; Myocardial Reperfusion Injury ; enzymology ; metabolism ; prevention & control ; Nitric Oxide Synthase Type I ; metabolism ; physiology ; Rabbits ; Random Allocation ; Time Factors

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

OBJECTIVETo investigate the effect of kappa-Opioid receptors in the cardioprotection elicited by ischemic postconditioning and the underlying mechanism.

METHODSThe isolated perfused hearts of male Sprague-Dawley rats were subjected to 30 min of global ischemia followed by 120 min of reperfusion. formazan content of myocardium was measured spectrophotometrically, and the level of lactate dehydrogenase (LDH) in the coronary effluent was also measured. In isolated ventricular myocytes hypoxia postconditioning was achieved by 3 cycles of 5 min reoxygenation/5 min hypoxia starting at the beginning of reoxygenation, and cell viability was measured.

RESULTIn the Langendorff perfused rat heart model, ischemic postconditioning (6 cycles of 10 s reperfusion/10 s global ischemia starting at the beginning of reperfusion) increased formazan content, reduced LDH release, improved the recovery of the left ventricular developed pressure, maximal rise/fall rate of left ventricular pressure, left ventricular end-diastolic pressure and rate pressure product (left ventricular developed pressure multiplied by heart rate), attenuated the decrease of coronary flow during reperfusion and increased the isolated cell viability. Pretreatment with nor-BNI, an antagonist of kappa-Opioid receptors and mitoK(ATP) blocker 5-HD attenuated the effect of ischemic/hypoxic postconditioning.

CONCLUSIONPostconditioning may protect myocardium against ischemia/reperfusion injury via activating kappa-Opioid receptors and mitoK(KATP).

Animals ; In Vitro Techniques ; Ischemic Preconditioning, Myocardial ; methods ; L-Lactate Dehydrogenase ; metabolism ; Male ; Myocardial Reperfusion Injury ; metabolism ; physiopathology ; prevention & control ; Myocardium ; metabolism ; pathology ; Potassium Channels ; metabolism ; physiology ; Rats ; Rats, Sprague-Dawley ; Receptors, Opioid, kappa ; metabolism ; physiology

OBJECTIVETo test whether postconditioning could inhibit the expression of phospho-JNK (P-JNK) mitogen activated protein kinase (MAPK) and study its relation to apoptosis of cardiocyte.

METHODSSixty rats were randomly divided into six groups: sham, reperfusion injury (R/I), postconditioning (Post), SP600125 (I_JNK), anisomycin and postconditioning (Ani+Post) and anisomycin (Ani) groups. After acute myocardial infarction was induced in rats, placebo solution (DMSO), SP600125 (6 mg/kg) or anisomycin (2 mg/kg) was injected through jugular vein 5 min before reperfusion; 6 h later 3 rats of each group were executed and the hearts were separated to measure the signaling molecules (phospho-JNK, TNF alpha, Caspase-8, Bcl-2/Bax, cytochrome-c). Twenty-two hours later hemodynamic data were measured in the left rats, and then blood samples were taken to determine serum markers of cardiac damage, and hearts were separated to measure the infarction area and cardiocyte apoptosis.

RESULTPostconditioning improved +/-DP/DTmax of left ventricle, limited infarct area, relieved apoptosis and necrosis of cardiocytes, and inhibited the expression of P-JNK (1.12 +/-0.21 Compared with 1.90 +/-0.32, P<0.05). At the same time the levels of TNFalpha Caspase-8, Bax and Cyt-c were lower in Post group than those in R/I group, but Bcl-2 expression levels were higher. I_JNK group presented the similar protection effect of postconditioning [TUNEL index: (6.23 +/-2.43)% Compared with (18.22 +/-5.10)%, P<0.05; Infarct area: (23.44 +/-6.34)% Compared with (42.31 +/-8.21)%, P<0.05]. On the other hand, Ani+Post group partially lost cardioprotection effect [TUNEL index: (14.12 +/-2.00)% Compared with (18.22 +/-5.10)%,P>0.05; Infarct area: (35.27 +/-5.28)% Compared with (42.31+/-8.21)%,P>0.05], because of the activation of JNK MAPK.

CONCLUSIONPostconditioning can inhibit phosphorylation of JNK MAPK, which attenuates cardiocyte apoptosis by both extrinsic and mitochondria pathway.

Animals ; Apoptosis ; drug effects ; Ischemic Preconditioning, Myocardial ; JNK Mitogen-Activated Protein Kinases ; metabolism ; pharmacology ; Male ; Myocardial Infarction ; enzymology ; pathology ; therapy ; Myocardial Reperfusion Injury ; prevention & control ; Myocytes, Cardiac ; enzymology ; pathology ; Random Allocation ; Rats ; Rats, Sprague-Dawley