Possible role of adrenergic component and cardiac mast cell degranulation in preconditioning-induced cardioprotection.

The present study was designed to investigate the role of adrenergic component and cardiac mast cell degranulation in the cardioprotective effect of ischaemic preconditioning. Isolated rat hearts were subjected to 30 min of global ischaemia followed by 30 min of reperfusion. Ischaemic/norepinephrine (100 microm) preconditioning markedly reduced ischaemia-reperfusion-induced release of lactate dehydrogenase (LDH) and creatine kinase (CK) in coronary effluent and the incidence of ventricular premature beats (VPBs) and ventricular tachycardia/fibrillation (VT/VF) during the reperfusion phase. Moreover, ischaemic/norepinephrine preconditioning significantly reduced ischaemia-reperfusion-induced release of mast cell peroxidase (MPO), a marker of mast cell degranulation. Prazosin (0.1 microm), a alpha(1)adrenoceptor blocker, administered during ischaemic/norepinephrine preconditioning attenuated the cardioprotective and antiarrhythmic effect of ischaemic/norepinephrine preconditioning. MPO release increased immediately after ischaemic/norepinephrine preconditioning and the release was found to be inhibited in hearts subjected to ischaemic/norepinephrine preconditioning in the presence of prazosin. However, prazosin (0.1 microm) treatment per se produced cardioprotective and antiarrhythmic effects and reduced ischaemia-reperfusion-induced MPO release. These findings tentatively suggest that ischaemic preconditioning produced cardioprotective and antiarrhythmic effect by activating alpha(1)adrenoceptors and consequent degranulation of cardiac mast cells. Prazosin administered during ischaemic preconditioning abolished its ameliorative effect. 1999 Academic Press@p$hr Copyright 1999 Academic Press.     

Cardioprotective effects of mast cell modulators in ischemia-reperfusion-induced injury in rats

This study was designed to investigate the cardioprotective effects of pharmacological interventions, modulating resident cardiac mast cells, on ischemia-reperfusion-induced injury. Isolated rat hearts were mounted on Langendorff apparatus and subjected to 30-min global ischemia followed by 120-min reperfusion. The extent of mast cell degranulation was assessed by release of mast cell peroxidase (MPO). The release of lactate dehydrogenase (LDH) and creatine kinase (CK) and estimation of infarct size were used to assess the extent of myocardial injury. Left ventricle developed pressure (LVDP) and its derivatives, that is, dp/dt(max) and dp/dt(min), were recorded to evaluate the postischemic recovery of the contractility of heart. Ketotifen (0.1 microM) and low-dose carvedilol (0.1 microM), without beta-blockade activity, attenuated ischemia-reperfusion-induced mast cell degranulation along with the reduction in myocardial injury, suggesting the protective effects of mast cell stabilization during ischemia and reperfusion. Administration of compound 48/80 (1 microg/ml), a specific mast cell degranulating agent, completely degranulated cardiac mast cells before global ischemia. Moreover, it also resulted in the attenuation of ischemia-reperfusion-induced myocardial injury. Decreased release of cytotoxic mediators from already degranulated (empty) mast cells during sustained global ischemia may be responsible for the cardioprotective effects of compound 48/80. Administration of carvedilol or ketotifen after compound 48/80 perfusion did not further enhance the cardioprotective effects, suggesting that the cardiac mast cells may be the common target site for ketotifen, compound 48/80 and low-dose carvedilol.     

Possible role of nitric oxide and mast cells in endotoxin-induced cardioprotection.

The present study is designed to investigate the role of nitric oxide (NO) and cardiac mast cells in the cardioprotective effect of endotoxin in isolated rat heart subjected to 30 min of global ischaemia and 30 min of reperfusion. Endotoxin (2.5 mg kg(-1); i.p.) was administered 8 h before subjecting the heart to global ischaemia. Endotoxin pretreatment markedly reduced the release of lactate dehydrogenase (LDH) and creatine kinase (CK), markers of cardiac injury, in coronary effluent and the percentage incidence of ventricular premature beats (VPBs) and ventricular tachycardia/fibrillation (VT/VF) during the reperfusion phase. Endotoxin pretreatment significantly increased the release of nitrite prior to and after global ischaemia. On the other hand, endotoxin pretreatment decreased the release of mast cell peroxidase (MPO) during the reperfusion phase. The cardioprotective and antiarrhythmic effect of endotoxin pretreatment was abolished by dexamethasone (3 mg kg(-1); i.p.) or l -canavanine (20 mg kg(-1); i.p.) given 1 h before the administration of endotoxin. It is proposed that the cardioprotective and antiarrhythmic effect of the endotoxin may be ascribed to the induction of nitric oxide synthase (NOS) and subsequent increase in the release of NO. NO may stabilize cardiac mast cells and consequently decrease the release of cytotoxic mediators from these cells. Prevention of degranulation of cardiac mast cells may be responsible for the cardioprotective and antiarrhythmic effects of the endotoxin.     

Role of angiotensin in cardioprotective effect of ischemic preconditioning

This study was designed to investigate the role of angiotensin (Ang II) in the cardioprotective effect of ischemic preconditioning. Isolated perfused rat heart was subjected to global ischemia for 30 min followed by reperfusion for 120 min. Coronary effluent was analyzed for lactate dehydrogenase (LDH) and creatine kinase (CK) release to assess the degree of cardiac injury. Myocardial infarct size was estimated macroscopically by using triphenyl tetrazolium chloride (TTC) staining. Four episodes of ischemic/Ang II preconditioning markedly reduced LDH and CK release in the coronary effluent and decreased myocardial infarct size. The cardioprotective effect of Ang II preconditioning was abolished by CV 11974, AT1-receptor antagonist, whereas no such effect was noted with CV 11974 in ischemic preconditioning. PD 123319, AT2-receptor antagonist, produced no marked effect on Ang II preconditioning and ischemic preconditioning induced reduction in myocardial injury. On the basis of these results, it may be concluded that activation of AT1 receptors may be involved in angiotensin-induced pharmacologic preconditioning. But it may not be involved in the cardioprotective effect of ischemic preconditioning in isolated rat heart.     

Targeting cardiac mast cells: pharmacological modulation of the local renin-angiotensin system

Enhanced production of angiotensin II and excessive release of norepinephrine in the ischemic heart are major causes of arrhythmias and sudden cardiac death. Mast cell-dependent mechanisms are pivotal in the local formation of angiotensin II and modulation of norepinephrine release in cardiac pathophysiology. Cardiac mast cells increase in number in myocardial ischemia and are located in close proximity to sympathetic neurons expressing angiotensin AT1- and histamine H3-receptors. Once activated, cardiac mast cells release a host of potent pro-inflammatory and pro-fibrotic cytokines, chemokines, preformed mediators (e.g., histamine) and proteases (e.g., renin). In myocardial ischemia, angiotensin II (formed locally from mast cell-derived renin) and histamine (also released from local mast cells) respectively activate AT1- and H3-receptors on sympathetic nerve endings. Stimulation of angiotensin AT1-receptors is arrhythmogenic whereas H3-receptor activation is cardioprotective. It is likely that in ischemia/reperfusion the balance may be tipped toward the deleterious effects of mast cell renin, as demonstrated in mast cell-deficient mice, lacking mast cell renin and histamine in the heart. In these mice, no ventricular fibrillation occurs at reperfusion following ischemia, as opposed to wild-type hearts which all fibrillate. Preventing mast cell degranulation in the heart and inhibiting the activation of a local renin-angiotensin system, hence abolishing its detrimental effects on cardiac rhythmicity, appears to be more significant than the loss of histamine-induced cardioprotection. This suggests that therapeutic targets in the treatment of myocardial ischemia, and potentially congestive heart failure and hypertension, should include prevention of mast cell degranulation, mast cell renin inhibition, local ACE inhibition, ANG II antagonism and H3-receptor activation.     

POSSIBLE MECHANISM OF CARDIOPROTECTIVE EFFECT OF ISCHAEMIC PRECONDITIONING IN ISOLATED RAT HEART

The present study is designed to investigate the mechanism of the cardioprotective effect of ischaemic preconditioning. Isolated perfused rat heart was subjected to global ischaemia for 30 min followed by reperfusion for 120 min. Coronary effluent was analysed for LDH and CK release to assess the degree of cardiac injury. Myocardial infarct size was estimated macroscopically using TTC staining. Four episodes of ischaemic preconditioning markedly reduced LDH and CK release in the coronary effluent and decreased myocardial infarct size. Administration of prazosin (alpha(1)adrenoceptor antagonist) before global ischaemia reduced the extent of ischaemia-reperfusion induced myocardial injury. The cardioprotective effect of ischaemic preconditioning was abolished by prazosin and colchicine (microtubule disaggregator). On the basis of these results, it may be concluded that the cardioprotective effects of ischaemic preconditioning may be mediated through stimulation of alpha(1)adrenoceptors and translocation of PKC.     

Ischaemic preconditioning and mast cell histamine release: microdialysis of isolated rat hearts.

The aim of this study was to investigate the feasibility of intramyocardium kinetics of histamine release by microdialysis in the isolated rat heart and ascertain if the inhibition of histamine release is implicated in the antiarrhythmic effect of preconditioning. A 30 min normothermic global ischaemia model followed by 30 min reperfusion was carried out in the control group (n= 9). In the preconditioning group (n= 8) there was a 5 min global ischaemia followed by 10 min of reperfusion. A mast cell stabilizing group received the disodium cromoglycate ( 10 micro M, n= 10). The last group received a mast cell degranulator, compound 48/80 (1micro g ml (-1), n= 10). In the control group, the histamine release during reperfusion was significantly different from the basal concentration ( 18.4 +/- 6.5 vs 1.9 +/- 0.5 nM, P< 0.05) and was associated with a maximal period of severe arrhythmias. The ischaemic preconditioning modified the histamine release kinetics with an early mast cell degranulation ( 9.7 +/- 1.5 nM) and a significant decrease in the total period of severe arrhythmias in comparison with the control group ( P< 0.05). In the disodium cromoglycate group, the histamine release during reperfusion decreased ( 3.1 +/- 0.7 nM) and was associated with a maximal period of severe arrhythmias. In the C48/80 group, the increase in the histamine released during reperfusion ( 21.2 +/- 5.0 nM) was associated with a maximal period of severe arrhythmias. These results showed firstly the feasibility of kinetic histamine release in myocardium interstitial fluid on the isolated rat heart and secondly that the inhibition of histamine release did not play a direct role in the antiarrhythmic effect of preconditioning.     

Mechanism of cardioprotective effect of erythropoietin-induced preconditioning in rat heart

Objective:

The cardioprotective potential of human recombinant erythropoietin (alpha) (Epo) against ischemia-reperfusion-induced injury is well known. But, the underlying mechanisms are not well elucidated. The aim of this study was to characterize the mechanism involved in the cardioprotective effect of Epo-induced preconditioning in isolated rat heart.

Materials and Methods:

The heart was mounted on a Langendorff apparatus. After 10 min of stabilization, four cycles of ischemic preconditioning (IPC) were given followed by 30 min of global ischemia and 120 min of reperfusion. Epo preconditioning was induced by four cycles of 5-min perfusion of K-H solution containing Epo (1.0 U/ml) followed by 5 min perfusion with K-H solution. Myocardial infarct size was estimated macroscopically using the triphenyltetrazolium chloride staining technique. The extent of myocardial injury was measured by release of lactate dehydrogenase and creatine kinase-MB in the coronary effluent.

Results:

The present study demonstrates that Epo preconditioning was almost as effective as IPC. Administration of Wortmannin (100 nM), a PI-3K inhibitor, or Chelerythrine (1 µM), a protein kinase-C (PKC) inhibitor, or AG490 (5 µM), a JAK-2 inhibitor, significantly attenuated the cardioprotective effects of Epo-induced preconditioning.

Conclusion:

Our result suggest that the cardioprotective potential of Epo-induced preconditioning in isolated rat heart was due to an interplay of the JAK-2, PI-3K and PKC pathways. Inhibition of any one of the three pathways was sufficient to block the cardioprotective effect of Epo-induced preconditioning in isolated rat heart.     

缺血预处理对离体大鼠心脏肌钙蛋白T释放的影响

目的 :探讨缺血预处理对离体大鼠再灌注期释放心肌肌钙蛋白 T(Tn T)的影响。方法 :实验采用L angendorff灌流装置 ,单次 5 m in缺血 ,继 10 min再灌注作为预处理模型。于 2 0 min缺血后 6 0 min再灌注 ,测定冠流液Tn T、磷酸肌酸激酶 (CK)、乳酸脱氢酶 (L DH)和左室内压 (L VP)。结果 :缺血预处理能明显减少 Tn T、CK、L DH的释放 ,也能改善左室心肌收缩功能。∑Tn T或再灌注 6 0 m in时的 Tn T与 L VP有明显相关性。结论 :Tn T可以作为一个有效的生化指标来判断左室功能障碍和心肌受损程度 ,缺血预处理能减轻心肌缺所致的心肌损伤并改善左室功能     

Inhibition of cardiac tumor necrosis factor-alpha production by calcitonin gene-related peptide-mediated ischemic preconditioning in isolated rat hearts

Previous investigations have demonstrated that calcitonin gene-related peptide (CGRP) plays an important role in the mediation of ischemic preconditioning in rats. In the present study, we examined signal transduction pathways of CGRP-mediated ischemic preconditioning. Thirty minutes of global ischemia and 40 min of reperfusion caused a dramatic decrease in myocardial function, and a significant increase in the release of cardiac creatine kinase in the coronary effluent and in the content of tumor necrosis factor-alpha (TNF-alpha) in myocardial tissues. However, ischemic preconditioning (three cycles of 5-min ischemia and 5-min reperfusion) or pretreatment with CGRP for 5 min dramatically improved the recovery of cardiac function, and reduced the release of cardiac creatine kinase and the TNF-alpha content. The effect of ischemic preconditioning was abolished by CGRP-(8-37), the selective CGRP receptor antagonist, and by capsaicin, which depletes sensory nerve neurotransmitter content, but was unaltered by treatment with glibenclamide, a blocker of the ATP-sensitive potassium (K(ATP)) channel. The protective effects of exogenous CGRP-induced preconditioning were also not blocked by glibenclamide. These results suggest that the cardioprotective effects afforded by CGRP-mediated ischemic preconditioning are related to inhibition of cardiac TNF-alpha production, but not to activation of the K(ATP) channel.     

Relaxin induces mast cell inhibition and reduces ventricular arrhythmias in a swine model of acute myocardial infarction.

Resident cardiac mast cells, located mainly around coronary vessels and in the right atrium close to the sinoatrial node, are the main repository of cardiac histamine. Inflammatory activation of cardiac mast cells, as occurs upon acute myocardial infarction, causes the release of histamine and prostanoids. These substances lead to severe tachyarrhythmias, cardiodepressive effects and coronary spasm, thus contributing to myocardial damage and early, lethal outcome. Relaxin, known to inhibit mast cell activation, has been recently validated as a cardiotropic hormone, being produced by the heart and acting on specific heart receptors. In this study, we report on a swine model of heart ischemia/reperfusion, currently used to test cardiotropic drugs, in which human recombinant relaxin (2.5 and 5 microg/kg b.w.), given at reperfusion upon a 30-min ischemia, markedly reduced cardiac injury as compared with the vehicle-treated animals. Evidence is provided that relaxin, at both the assayed doses, causes a clear-cut, significant reduction of plasma histamine, increase in cardiac histamine content and decrease in cardiac mast cell degranulation. This is accompanied by a reduction of oxidative cardiac tissue injury (assessed as tissue malondialdehyde) and of the occurrence of severe ventricular arrhythmias. In conclusion, this study provides further insight into the cardioprotective effects of relaxin, which also involve mast cell inhibition, and confirms the relevance of histamine in the pathophysiology of ischemia-reperfusion-induced cardiac injury and dysfunction. It also offers additional evidence for the potential therapeutic effects of relaxin in animal models of disease involving mast cell activation.     

Fenofibrate attenuates impaired ischemic preconditioning-mediated cardioprotection in the fructose-fed hypertriglyceridemic rat heart

We investigated in this study whether or not the ischemic preconditioning (IPC)-mediated cardioprotective effect against ischemia–reperfusion (I/R) injury exists in the fructose-fed hypertriglyceridemic (HTG) rat heart. Langendorff-perfused normal and fructose-fed (10 %?w/v in drinking water, 8 weeks) HTG rat hearts were subjected to 30-min global ischemia and 120-min reperfusion. IPC protocol included four brief episodes (5 min each) of ischemia and reperfusion. Myocardial infarct size using triphenyltetrazolium chloride staining, markers of cardiac injury such as lactate dehydrogenase (LDH) and creatine kinase (CK-MB) release, coronary flow rate (CFR), and myocardial oxidative stress were assessed. High degree of myocardial I/R injury, by means of significant myocardial infarct size, elevated coronary LDH and CK-MB release, reduced CFR, and high oxidative stress, was noted in the HTG rat heart as compared to the normal rat heart. The IPC-mediated cardioprotection against I/R injury was markedly impaired in the HTG rat heart as compared to the normal rat heart. Interestingly, pharmacological reduction of triglycerides using 8-week treatment protocol with fenofibrate (80 mg/kg/day, p.o.) restored the IPC effect in the HTG rat heart that was blunted by coinfusion, during the IPC reperfusion protocol, of a specific inhibitor of phosphoinositide-3-kinase (PI3-K), wortmannin (100 nM). The IPC failed to protect the HTG rat heart against I/R injury. Fenofibrate treatment reduced high triglycerides in the fructose-fed HTG rat and subsequently restored the cardioprotective effect of IPC.     

前列腺素介导缓激肽诱导预适应对缺血再灌心肌的保护作用(英文)

在大鼠离体心脏观察了前列腺素介导缓激肽诱导的预适应对缺血再灌心肌的保护作用．３０ｍｉｎ缺血和３０ｍｉｎ再灌引起心功能降低（左室内压和左室内压最大上升速率下降）,冠脉流量和心率降低以及肌酸激酶（ＣＰＫ）释放增加．缺血预适应（５ｍｉｎ缺血,５ｍｉｎ再灌,重复３次）能显著改善心功能,促进心率和冠脉流量的恢复,减少ＣＰＫ释放．其作用不受吲哚美辛（１０μｍｏｌ·Ｌ－１预先灌流３０ｍｉｎ）影响．预先用缓激肽（０．５μｍｏｌ·Ｌ－１）处理５ｍｉｎ产生缺血预适应样心肌保护作用,表现为促进心功能恢复,减少ＣＰＫ释放．该作用被预先灌流吲哚美辛取消．对照组,缺血再灌组,缓激肽组,吲哚美辛加缓激肽组的ＣＰＫ分别为（０．２８±０．０３）,（２．２３±０．０６）,（０．３９±０．０９）,（１．８７±０．０５）μｍｏｌ·ｍｉｎ－１·ｇ－１湿组织．结果提示：缓激肽诱导预适应对缺血再灌心肌的保护作用与促前列腺素生成有关     

Inhibitory effect of calcium antagonists on the depletion of cardiac norepinephrine during postischemic reperfusion

We have investigated whether Ca2+ antagonists of the dihydropyridine type (nifedipine, nisoldipine, and nitrendipine) attenuate or abolish the ischemia-reperfusion-induced depletion of the cardiac stores of norepinephrine (NE). The experiments were performed using isolated, Langendorff-perfused rat hearts. Ischemia (global) was induced for 15 or 60 min at 37 degrees C and was followed by normothermic reperfusion. Left ventricular NE content was assayed by high-performance liquid chromatography with electrochemical detection. The continued presence of nifedipine (0.03 microM), nisoldipine (0.03 microM), or nitrendipine (0.03 microM) before and after the ischemic episode abolished the loss of NE caused by 15 min but not 60 min of ischemia and reperfusion. Nifedipine, 0.03 microM, but not diltiazem, 0.24-1.22 microM, or verapamil, 0.22-1.09 microM, attenuated (p less than 0.05) NE depletion when added only on reperfusion.     

Protection of calcitonin gene-related peptide-mediated preconditioning against lysophosphatidylcholine-induced myocardial injury in isolated rat hearts

研究心脏缺血预适应（ＰＣ）对溶血性磷脂酰胆碱（ＬＰＣ）损伤心肌作用的影响，并探讨降钙素基因相关肽（ＣＧＲＰ）在ＰＣ中的作用．离体大鼠心脏Ｌａｎｇｅｎｄｏｒｆ法灌流，记录心率，冠脉流量，左室压和左室压最大上升速率（＋ｄｐ／ｄｔｍａｘ），并测定灌流液中肌酸磷酸激酶（ＣＰＫ）含量．结果显示，ＬＰＣ能降低各项心功能指标，并使ＣＰＫ释放增加；ＰＣ（缺血５ｍｉｎ，再灌５ｍｉｎ，重复３次）能减轻ＬＰＣ的损伤作用；ＰＣ的心肌保护作用可被选择性ＣＧＲＰ受体拮抗剂ＣＧＲＰ８－３７所取消；预先给予ＣＧＲＰ或辣椒素能产生与ＰＣ相同的心肌保护作用．对照组，ＬＰＣ，ＰＣ＋ＬＰＣ，ＣＧＲＰ８－３７，ＣＧＲＰ８－３７＋ＰＣ＋ＬＰＣ，ＣＧＲＰ＋ＬＰＣ，ＣＧＲＰ８－３７＋ＣＧＲＰ＋ＬＰＣ，辣椒素＋ＬＰＣ组ＣＰＫ释放量分别为０．２６±０．０５，２．３０±０．２２，０．２５±０．０３，０．３０±０．０８，２．６０±０．１５，０．２４±０．０５，２．７０±０．２０和０．２５±０．０７μｍｏｌ·ｍｉｎ－１·ｇ－１湿组织．这些结果提示：１）ＰＣ对ＬＰＣ所致心肌损伤具有保护作用；２）ＰＣ的保护作用是由ＣＧＲＰ所介导；３）ＣＧＲＰ或辣椒素可模拟ＰＣ的保护作?     

Reduction of ischemic, pharmacological and remote preconditioning effects by an antioxidant N-acetyl cysteine pretreatment in isolated rat heart

The present study was designed to investigate the possible role of free radicals in cardioprotective effects of ischemic, pharmacological and remote preconditioning. Isolated rat heart was perfused on Langendorff apparatus with Kreb's Henseleit solution and subjected to 30 min global ischemia followed by 120 min reperfusion. To assess myocardial injury, coronary effluent was analyzed for lactate dehydrogenase and creatine kinase activity. Myocardial infarct size was estimated using triphenyl tetrazolium chloride staining. Ischemic preconditioning, pharmacological preconditioning (angiotensin II; H2O2), remote aortic preconditioning markedly attenuated I/R induced increase in lactate dehydrogenase and creatine kinase release and myocardial infarct size. Administration of N-Acetyl Cysteine (NAC), in vitro, during ischemic and pharmacological, and in vivo during remote preconditioning attenuated the cardioprotective effects of preconditioning. On the basis of these results, it may be concluded that sub threshold generation of Reactive Oxygen Species (ROS) may activate redox signaling which may be responsible for preconditioning induced cardioprotection.     

The cardioprotective effects of nitroglycerin-induced preconditioning are mediated by calcitonin gene-related peptide

Previous investigations have shown that endogenous calcitonin gene-related peptide (CGRP) may play an important role in the mediation of ischemic preconditioning and that nitroglycerin evokes the release of CGRP. In the present study, we examined whether nitroglycerin provides a preconditioning stimulus, and whether the cardioprotective effects of nitroglycerin-induced preconditioning involve endogenous CGRP. Thirty minutes of global ischemia and 30 min of reperfusion caused a significant impairment of cardiac contractile function and an increased release of creatine kinase. Pretreatment with nitroglycerin at the concentration of 3x10(-7) or 10(-6) M for 5 min produced a significant improvement of cardiac function and a decrease in the release of creatine kinase. The content of CGRP-like immunoreactivity in coronary effluent was increased during nitroglycerin perfusion. However, the cardioprotection afforded by nitroglycerin was abolished by CGRP-(8-37) (10(-7) M), a selective CGRP receptor antagonist. Pretreatment with capsaicin (50 mg/kg, s.c.), which specifically depletes the transmitter content of sensory nerves, also abolished the protective effects of nitroglycerin and markedly reduced the release of CGRP from the heart during nitroglycerin perfusion. These findings suggest that nitroglycerin-induced preconditioning is related to stimulation of CGRP release in rat hearts.     

Ischemic preconditioning of remote organs attenuates gastric ischemia-reperfusion injury through involvement of prostaglandins and sensory nerves

Limitation of the stomach damage by its earlier brief ischemia and reperfusion before prolonged ischemia is defined as gastric ischemic preconditioning but whether such brief ischemia of remote organs like heart or liver can also attenuate the gastric damage caused by longer and severe ischemia-reperfusion remains unknown. The cardiac, hepatic and gastric preconditioning were induced by brief ischemia (occlusion of coronary, hepatic and celiac arteries twice for 5 min) applied 30 min before 3 h of ischemia/reperfusion. Standard 3 h ischemia-reperfusion of the stomach produced numerous gastric lesions, decreased gastric blood flow and mucosal prostaglandin E2 generation and increased expression and plasma release of interleukin-1beta and tumor necrosis factor-alpha (TNF-alpha). These effects were significantly attenuated by brief cardiac, hepatic and gastric preconditioning which upregulated cyclooxygenase-2 mRNA but not cyclooxygenase-1 mRNA. The protective effects of brief gastric, cardiac and hepatic preconditioning were attenuated by selective cyclooxygenase-1 and cyclooxygenase-2 inhibitors and capsaicin denervation. We conclude that brief ischemia of remote preconditioning such as heart or liver protects gastric mucosa against severe ischemia-reperfusion-induced gastric lesions as effectively as local preconditioning of the stomach itself via the mechanism involving prostaglandin derived from cyclooxygenase-1 and cyclooxygenase-2 and the activation of sensory nerves releasing calcitonin gene-related peptide (CGRP) combined with the suppression of interleukin-1beta and TNF-alpha expression and release.     

Mediation of calcitonin gene-related peptide in protection of ischemic preconditioning in rat hindlimbs.

AIM: To study modulation of calcitonin gene-related peptide (CGRP) in the protective effect of ischemic preconditioning on endothelial cells. METHODS: Rat hindlmbs were subjected to ischemia for 2 h, and endothelium-dependent vasorelaxation to acetylcholine (ACh) was examined in rat hindlimbs. RESULTS: Two hours of ischemia elicited no effect on vasoconstrictor responses to norepinephrine, but markedly impaired vasodilator responses to ACh. Ischemic preconditioning induced by 5-min aortic occlusion and 10-min blood reperfusion prevented the impairment of vasorelaxation to ACh due to long-term ischemia. The protection of ischemic preconditioning was abolished by repeated pretreatments with capsaicin to deplete CGRP. Acute application of capsaicin to evoke CGRP release or CGRP caused an ischemic preconditioning-like protection. CONCLUSION: Capsaicin-sensitive sensory nerves are involved in the protective effect of ischemic preconditioning on endothelial cells in the rat hindlimbs, and CGRP can mimic the protective effect of ischemic preconditioning in blood vessels.     

降钙素基因相关肽对大鼠小肠缺血预适应的保护作用

目的探讨降钙素基因相关肽(CGRP)在大鼠小肠缺血预适应中的作用及意义。方法①健康Wistar雄性大鼠,体质量(280±30)g,分为3组(各8只),对照组(CON):仅分离肠系膜上动脉(SMA),不夹闭,观察90 min;缺血再灌组(I/R):分离SMA,夹闭30 min,再灌注60 min,结束实验;缺血预适应组(IP):分离SMA,夹闭SMA 5 min反复3次,然后再夹闭30 min,再灌注60 min,结束实验。②利用放射免疫法测定CGRP含量,以乳酸脱氢酶(LDH)、丙二醛(MDA)含量变化和形态学变化为指标,评价缺血再灌注损伤。结果缺血预适应可明显抑制大鼠小肠缺血再灌注损伤后LDH的水平增高,降低MDA的含量(P<0.01),保护小肠黏膜不受损伤。结论CGRP为大鼠小肠缺血再灌注损伤中关键性介质之一,缺血预适应可提高大鼠小肠缺血再灌注后CGRP的水平,对抗缺血再灌注损伤。