L-Arginine given after ischaemic preconditioning can enhance cardioprotection in isolated rat hearts.

OBJECTIVE: Ischaemic or pharmacological preconditioning with L-arginine has been reported to be insufficient for optimal cardioprotection. The ability of nitric oxide (NO) to enhance ischaemic preconditioning was assessed, and the role of L-arginine-induced ischaemic preconditioning in myocardial protection was determined. METHODS: Isolated rat hearts were prepared and divided into six groups: control hearts (control, n=6) were perfused without global ischaemia at 37 degrees C for 160 min; global ischaemia hearts (GI, n=6) were subjected to ischaemia for 20 min and reperfusion for 120 min; ischaemic preconditioned hearts (IP, n=6) received 2 min of zero-flow global ischaemia followed by 5 min reperfusion, before 20 min of global ischaemia; L-arginine hearts (ARG, n=6) received 1 mmol/l L-arginine for 5 min, before 20 min of global ischaemia; ischaemic preconditioning plus nitro-L-arginine methyl ester hearts (IP+L-NAME, n=6) received 2 min of ischaemic preconditioning and 5 min reperfusion with 3 mmol/l L-NAME in Krebs-Henseleit buffer, before 20 min of global ischaemia; and ischaemic preconditioning plus L-arginine hearts (IP+ARG, n=6) received 2 min of ischaemic preconditioning and 5 min reperfusion with 1 mmol/l L-arginine in Krebs-Henseleit buffer. Haemodynamic parameters and coronary flow were recorded continuously. Nitrites and nitrates (NOx) were measured 5 and 60 min after reperfusion, and infarct size was also determined. RESULTS: In the IP+ARG group, significant amelioration and preservation of left ventricular peak developed pressure and coronary flow was observed compared with the GI, IP, ARG and IP+L-NAME groups. Infarct size in the IP+ARG group was reduced significantly compared with that in the GI, IP, ARG and IP+L-NAME groups. Significant preservation of NOx was observed during reperfusion in the IP+ARG group compared with the GI group. CONCLUSIONS: Inhibition of NO synthase with L-NAME had little impact on ischaemic preconditioning, suggesting that endogenous NO is not a major mediator of ischaemic preconditioning. Nevertheless, enhancement of the effects of ischaemic preconditioning can be achieved with L-arginine, a precursor of NO, improving post-ischaemic functional recovery and infarct size in the isolated rat heart.     

Effect of sevoflurane preconditioning on ischaemia/reperfusion injury in the rat kidney in vivo

BACKGROUND AND OBJECTIVE: Whereas the protective effect of anaesthetic and ischaemic preconditioning has been described for several organs, it is uncertain whether this mechanism is also effective in the kidney. We compared the effect of preconditioning with sevoflurane and preconditioning with short episodes of ischaemia on renal ischaemia/reperfusion injury in the rat in vivo. METHODS: Fourteen days after right-sided nephrectomy, anaesthetized male Wistar rats were randomly assigned to a sham-operated group (no arterial occlusion, n = 5) or underwent 45 min of left renal artery occlusion (control group, n = 9) followed by 3 days of reperfusion. Two further experimental groups of animals were preconditioned prior to ischaemia either by administering 1 MAC sevoflurane for 15 min followed by 10 min of washout (sevoflurane group, n = 10) or by subjecting the animals to three short episodes of renal ischaemia (ischaemia-preconditioned group, n = 8). Blood creatinine was measured during reperfusion and morphological damage was assessed by histological examination. RESULTS: Baseline creatinine values were similar in all four groups (0.7 +/- 0.2 mg dL-1; mean +/- SD) and remained unchanged in the sham-operated animals after 3 days (0.8 +/- 0.2 mg dL-1). Creatinine levels increased in the ischaemic preconditioning group (3.3 +/- 1.2 mg dL-1) and sevoflurane preconditioning group (4.0 +/- 1.1 mg dL-1) compared to the control group (1.6 +/- 0.6 mg dL-1). Morphological damage was less severe in the control group, i.e. in animals without preconditioning, than in both preconditioning groups. CONCLUSION: Neither sevoflurane nor ischaemic preconditioning preserves renal function or attenuates cell damage in the rat in vivo.     

Microvascular preconditioning is not detectable by corrosion casting in the isolated perfused rat heart after 30 minutes of ischaemia

OBJECTIVE: Ischaemic preconditioning protects the myocardium from ischaemic injury and may also protect the vascular endothelium from the deleterious effects of ischaemia and reperfusion. We examined the possibility that ischaemic preconditioning might preserve the integrity of the coronary microcirculation following ischaemia and reperfusion. METHODS: Isolated rat hearts were perfused in Langendorff mode for 30 minutes and then subjected to 30 minutes of global ischaemia with or without ischaemic preconditioning (threexthree minute cycles). Some hearts underwent an additional 60 minutes of reperfusion. At the end of each protocol, microvascular corrosion casts were made by methylmethacrylate injection. RESULTS: Median left ventricular capillary density [interquartile range] after ischaemia was slightly but not significantly better with preconditioning at 6.8 [4.0-14.7]x10(-2) mm3.mg(-1) vs. 5.2 [2.6-7.1]x10(-2) mm3.mg(-1) (p=0.13). After 60 min of reperfusion, capillary density in preconditioned left ventricles was 20.7 [10.7-22.8]x10(-2) mm3.mg(-1) vs. 16.0 [10.2-23.0]x10(-2) mm3.mg(-1) for untreated ventricles (p=0.47). Coronary blood flow and heart rate were unchanged from before ischaemia. CONCLUSIONS: Ischaemia for 30 minutes induced global left ventricular capillary loss which was unmodified by preconditioning. We did not demonstrate vascular preconditioning using this model.     

Preconditioning the human heart.

The phenomenon of ischaemic preconditioning protects the myocardium by limiting infarct size in animal models of ischaemia and reperfusion. Ischaemic preconditioning may be induced by short periods of ischaemia and reperfusion. We investigated whether the human heart can be ischaemically preconditioned during coronary artery bypass grafting (CABG). Patients were enrolled into two separate studies. In the first study myocardial adenosine triphosphate (ATP) was used as the measured endpoint, assayed from myocardial biopsies taken at onset of cardiopulmonary bypass (CPB), at the end of the preconditioning stimulus, and at the end of a 10 min sustained ischaemic insult. In the second study the release of myocardial troponin T was used as the endpoint; taken at pre-CPB, and at 1, 6, 24, and 72 h after CPB. In both studies, patients were randomised into either the preconditioning group or the control group. Preconditioning was induced, after the onset of CPB, with two 3 min periods of crossclamping and an intervening 2 min of reperfusion, followed by 10 min sustained ischaemia. The control group only received 10 min of sustained ischaemia. Ischaemic preconditioning resulted in a slower rate of ATP (mumol/g dry weight) depletion in the preconditioned hearts at the end of the 10 min of sustained ischaemia (preconditioned: 11.5 +/- 0.8 vs control: 7.2 +/- 0.3; P < 0.005). Also, preconditioning resulted in a slower rate of troponin T release which was significantly different at 72 h after CPB in the preconditioned group (0.3 milligram) when compared with the control group (1.4 milligrams; P < 0.05). In addition, more patients in the preconditioned group had troponin T levels lower than 0.5 milligram at 72 h than in the control group (10 vs 3 patients). Both groups of patients received the same number of grafts, and underwent the same length of ischaemia during the procedure. We conclude that in patients undergoing CABG surgery, ischaemic preconditioning may reduce myocardial injury as shown by the favourable changes in myocardial ATP, and serum troponin T levels.     

-Arginine given after ischaemic preconditioning can enhance cardioprotection in isolated rat hearts

Objective: Ischaemic or pharmacological preconditioning with -arginine has been reported to be insufficient for optimal cardioprotection. The ability of nitric oxide (NO) to enhance ischaemic preconditioning was assessed, and the role of -arginine-induced ischaemic preconditioning in myocardial protection was determined. Methods: Isolated rat hearts were prepared and divided into six groups: control hearts (control, n=6) were perfused without global ischaemia at 37°C for 160 min; global ischaemia hearts (GI, n=6) were subjected to ischaemia for 20 min and reperfusion for 120 min; ischaemic preconditioned hearts (IP, n=6) received 2 min of zero-flow global ischaemia followed by 5 min reperfusion, before 20 min of global ischaemia; -arginine hearts (ARG, n=6) received 1 mmol/l -arginine for 5 min, before 20 min of global ischaemia; ischaemic preconditioning plus nitro- -arginine methyl ester hearts (IP+ -NAME, n=6) received 2 min of ischaemic preconditioning and 5 min reperfusion with 3 mmol/l -NAME in Krebs–Henseleit buffer, before 20 min of global ischaemia; and ischaemic preconditioning plus -arginine hearts (IP+ARG, n=6) received 2 min of ischaemic preconditioning and 5 min reperfusion with 1 mmol/l -arginine in Krebs–Henseleit buffer. Haemodynamic parameters and coronary flow were recorded continuously. Nitrites and nitrates (NOx) were measured 5 and 60 min after reperfusion, and infarct size was also determined. Results: In the IP+ARG group, significant amelioration and preservation of left ventricular peak developed pressure and coronary flow was observed compared with the GI, IP, ARG and IP+ -NAME groups. Infarct size in the IP+ARG group was reduced significantly compared with that in the GI, IP, ARG and IP+ -NAME groups. Significant preservation of NOx was observed during reperfusion in the IP+ARG group compared with the GI group. Conclusions: Inhibition of NO synthase with -NAME had little impact on ischaemic preconditioning, suggesting that endogenous NO is not a major mediator of ischaemic preconditioning. Nevertheless, enhancement of the effects of ischaemic preconditioning can be achieved with -arginine, a precursor of NO, improving post-ischaemic functional recovery and infarct size in the isolated rat heart.     

Ischaemic preconditioning protects the rat kidney from reperfusion injury.

OBJECTIVE: To examine the possible role of ischaemic preconditioning (IPC), an adaptive pathophysiological phenomenon that increases tolerance to ischaemia-reperfusion (I-R) injury, in renal protection when rats are presented with an I-R challenge. MATERIALS AND METHODS: Female Wistar rats (n=36) were divided randomly into four groups: (A) sham-operated controls; (B) IPC only; (C) renal ischaemia (RI) only; and (D) IPC+RI. The left kidney in groups B and D was preconditioned with four cycles of renal artery occlusion lasting 4 min, each occlusion separated by 11 min of reperfusion. The ischaemic insult, applied in groups C and D, comprised 40 min of sustained left renal artery occlusion. In Group D, the IPC cycle was completed 5 min before the start of the ischaemic insult. Differential left renal function was calculated by 99mTc-labelled dimercaptosuccinic acid scintigraphy at 0, 2 and 9 days after treatment, and expressed as a percentage of the total renal uptake. RESULTS: The mean (sem) maximum decrease in left renal function, to 14.5 (4.3)% of the total, occurred on day 2 in Group C. The equivalent value in Group D showed relative preservation of function, at 36.0 (3.5)% (P=0.001 compared with Group C). The mean left renal function improved by day 9, to 39.6 (6.7)% (Group C) and 48.6 (1.5)% (Group D). The mean left renal function in Group B (50.5-53.9%) did not differ from that in controls (49.4-51.4%). CONCLUSION: An IPC regimen applied 5 min before RI in the rat significantly protects it from the functional impairment associated with ischaemia and reperfusion.     

Effect of ischaemic preconditioning, cardiopulmonary bypass and myocardial ischaemic/reperfusion on free radical generation in CABG patients.

OBJECTIVE: To investigate the free radicals (FR) generation after ischaemic preconditioning and cardiopulmonary bypass and during reperfusion in CABG patients, and the role of ischaemic preconditioning. METHODS: Forty-three CABG patients were randomised into an ischaemic preconditioning and a control group. The protocol for ischaemic preconditioning was two cycles of 2-min ischaemia followed by 3-min reperfusion. Free radicals were measured using electron spin resonance spectroscopy. Global and right heart functions were collected. RESULTS: The free radicals generation in coronary sinus blood in the ischaemic preconditioning group was 9.7 and 16.6% after the ischaemic preconditioning protocol and 10 min after declamping, 6.8 and 13.3% in the controls. The free radicals in arterial samples were, respectively, 21, 14, 10 and 9% at 10 min, 1, 2 and 24 h after reperfusion. Cardiac index (CI) and right ventricular ejection fraction (RVEF) were improved by ischaemic preconditioning. CONCLUSION: Both ischaemic preconditioning and cardiopulmonary bypass induced free radicals generation. Although ischaemic preconditioning had no effect on free radicals generation after the operation, it protected against postoperative stunning.     

Hydrogen sulfide reduce renal ischemia/reperfusion injury by NOD-like receptor pathway

Objective To investigate whether the nod-like receptor (NLR) pathway is involved in protection of hydrogen sulfide (H2S) preconditioning during renal ischemia reperfusion. Methods Male Wistar rats were randomly divided into 3 groups: sham operation (Sham) group, renal ischemia/reperfusion (I/R) group subjected to occlusion of left renal pedicle for 45 min then reperfusion for 24 hours, and sodium hydrosulfide (NaHS) preconditioning group with continuous infusion of NaHS (300 nmol/min) by left renal artery for 15 min before I/R treatment. Renal injuries were evaluated by HE staining. The protein levels of NOD1, NOD2, nuclear NF-κB P65 and caspase-1 were analyzed by Western blot assay. The protein level of MCP-1 and IL-1β expressions was determined by immunohistochemical staining assay. Cell apoptosis were evaluated by Tunel staining assay. Results In I/R group, the renal NOD1 and NOD2 protein expressions were upregulated. Moreover, the nuclear NF-κB P65 expression was also elevated with an increase in its target genes-MCP-1 and IL-1β (All P＜0.01). HE staining revealed the existence of acute tubular necrosis in I/R kidney. TUNEL staining revealed more apoptotic cells in risk zone with the activation of caspase-1 of I/R-treated kidney(P＜0.01). NaHS preconditioning reversed I/R-induced increase in the expression of NOD1 and NOD2(P＜0.05). NaHS preconditioning also reduced I/R-induced activation of NF-κB P65 (P＜0.05) and upregulation of MCP-1 and IL-1β (P＜0.01). Moreover, NaHS preconditioning attenuated inflammation, repressed caspase-1 activation and reduced apoptotic cells after I/R. Conclusion Hydrogen sulfide preconditioning can alleviate renal ischemia/reperfusion injury by Nod-like receptor dependent on inflammatory pathway.     

ISCHAEMIC PRECONDITIONING OF THE LIVER: A PRELIMINARY STUDY

Background: A phenomenon of ‘preconditioning’ exists for the heart, but has not been described for the liver. This study was undertaken to determine whether a brief episode of ischaemia (3 or 5 min) followed by a short reperfusion time (5 or 10 min) would precondition the liver to reduce subsequent injury from prolonged ischaemia (30 to 90 min). Methods: Male Wistar rats were allocated into five control (no preconditioning) and five preconditioned groups, each having a liver resection. The preconditioning times were 3 rnin ischaemia followed by 5 rnin reperfusion with a prolonged ischaemia of 60 or 90 min for the first two groups, and 5 min ischaemia followed by 10 rnin reperfusion with prolonged ischaemia times of 30 or 45 min for the other three groups. Results: Of rats resected with 3–5–60 rnin time sequence designed to assess survival, 9/10 died. However 9/10 died also in the matching control group with 60 rnin ischaemia. With a 5–10–45 rnin sequence, 9/10 survived more than 24 h in the preconditioned group and 1/10 in the non-preconditioned controls. With a 5–10–30+ sequence designed to measure liver function tests, the prothrombin time was significantly improved; bilirubin, serum alkaline phosphatase and the alanine aminotransferase improved but these did not reach significance. Conclusion: A brief episode of ischaemia followed by an episode of reperfusion before a prolonged period of ischaemia ameliorated the effects of ischaemia-reperfusion injury in a rat liver resection model. If hepatic preconditioning is confirmed in humans, ischaemic preconditioning will have an important role for all liver surgery.     

Differential effect of preconditioning on post-ischaemic myocardial performance in the absence of substantial infarction and in extensively infarcted rat hearts.

OBJECTIVES: There is controversy concerning the beneficial effects of ischaemic preconditioning during short periods of ischaemia (stunning). The aim of the study was to investigate post-ischaemic myocardial performance after various periods of ischaemia in both non-preconditioned and preconditioned hearts and to compare these results with infarct volume estimation. METHODS: Isolated perfused rat hearts were subjected to various periods of sustained ischaemia (15, 20, 30, and 45 min). Haemodynamic parameters, infarct size and lactate dehydrogenase (LDH) leakage were recorded in both preconditioned and non-preconditioned hearts. RESULTS: After 15 min of ischaemia, preconditioned hearts revealed significantly lower developed pressure than non-preconditioned hearts (80+/-4.1 vs. 95+/-0.3%, P=0.02). In the 20 min ischaemia group, preconditioning resulted in non-significantly lower developed pressure (76+/-3.1% in preconditioned hearts vs. 87+/-5.3% in non-preconditioned hearts, P=0.11). In these groups infarct volume was small and not different between non-preconditioned and preconditioned hearts. After 30 min of ischaemia, preconditioning significantly improved developed pressure (66+/-3.1% in preconditioned and 44+/-5% in non-preconditioned hearts, P=0.002). LDH leakage was significantly higher in non-preconditioned hearts compared with preconditioned hearts (16+/-2.3 vs. 9.0+/-1.3, P=0.04), whereas infarct volume was not (12.5+/-0.8 and 9.8+/-1.5, respectively, P=0.1). Non-preconditioned hearts of this group, subjected to inotropic stimulation at the end of reperfusion, responded poorly. Significantly higher developed pressure was attained by preconditioned hearts (150+/-3.1 vs. 123+/-7.5%, P=0.01). After 45 min of ischaemia, preconditioning resulted in 69% limitation of infarct volume (P<0.0001) and 53% reduction in LDH release (P=0.009). Developed pressure was 57+/-8.5% in preconditioned hearts and 32+/-4.5% in non-preconditioned hearts (P=0.02). CONCLUSIONS: When ischaemic insult results in minimally lethal injuries, preconditioned hearts do not have the advantage of not being prone to stunning rather than non-preconditioned. If ischaemic insult is potentially able to produce extensive infarction, improvement in post-ischaemic myocardial function is mainly due to infarct size limitation evoked by preconditioning.     

硫化氢预处理延迟相对大鼠心肌缺血-再灌注损伤的保护作用

目的探讨硫化氢预处理延迟相对大鼠心肌缺血-再灌注损伤的保护作用。方法将30只健康成年SD雄性大鼠随机分为三组:假手术组(S组)、缺血-再灌注组(IR组)和硫化氢组(H组)。S组仅开胸并分离冠状动脉左前降支,但不阻断血流150min;IR组行冠状动脉左前降支阻断30min,再灌注120min;H组予以静脉注射NaHS0.05mg/kg,给药后24h同IR组处理。再灌注结束后检测血清超氧化物歧化酶(SOD)活性、丙二醛(MDA)含量和心肌梗死面积,电镜观察各组心肌细胞超微结构变化。结果与IR组比较,H组MDA含量降低,SOD活性增高(P<0.05),心肌梗死面积减少(P<0.05),电镜下H组心肌细胞损伤程度减轻。结论硫化氢预处理延迟相对大鼠缺血-再灌注心肌具有保护作用,与抗氧化反应有关。     

Ischaemic preconditioning but not isoflurane prevents post-ischaemic production of hydroxyl radicals in a canine model of ischaemia-reperfusion

BACKGROUND AND OBJECTIVE: Isoflurane has been shown to mimic ischaemic preconditioning (IPC). The protective effect of IPC, or applying isoflurane or perfusion with the 'push-pull' complex zinc-desferrioxamine (Zn-DFO) in the canine heart, was investigated. METHODS: Thirty minutes after salicylate administration (100 mg kg(-1)) the heart was exposed. All dogs were subjected to a 10 min left anterior descending artery occlusion followed by 2 h of reperfusion. In Group I (n = 9) isoflurane (2.5%) was administered 10 min prior to and during ischaemia. In Group II (n = 8), IPC was elicited by 5 min coronary artery occlusion, followed by 5 min of reperfusion, prior to the 10 min ischaemia. In Group III (n = 9) Zn-DFO (2.5 mg kg(-1)) was given 10 min prior to ischaemia. The effects of these interventions were compared to control (n = 10). Coronary sinus blood concentrations of salicylate, 2,3-dihydroxybenzoic acid (DHBA), lactate, pH and oxygen content were monitored. RESULTS: In the control group, 2,3-DHBA increased by 32% above the pre-ischaemic value (P < 0.05). In contrast, in the IPC hearts, a significant decrease in the production of 2,3-DHBA was observed (40% lower than baseline, P < 0.01). In the isoflurane group only a 13% (and non-significant) decrease was noticed. In the Zn-DFO group a 33% decrease was found (P < 0.01). The increase in lactate concentrations in the IPC and Zn-DFO groups was significantly smaller than that of control and isoflurane groups. CONCLUSIONS: IPC protected the heart against the deleterious effects of reperfusion, possibly by amelioration of the level of oxygen-derived reactive species, and the complete inhibition of reactive hydroxyl radical production. Isoflurane did not prove to be as effective in reducing the free radical damage.     

Preconditioning protects the guinea-pig urinary bladder against ischaemic conditions in vitro

AIMS: To investigate the ability of ischaemic preconditioning (IPC) to protect guinea-pig detrusor from damage caused by a subsequent more prolonged exposure to ischaemic conditions. MATERIALS AND METHODS: Smooth muscle strips were mounted for tension recording in small organ baths continuously superfused with Krebs' solution at 37 degrees C. Ischaemia was mimicked by removing oxygen and glucose from the superfusing solution. Contractile responses to electrical field stimulation (EFS) and carbachol were monitored. Three regimes of preconditioning were examined: 15, 10, and 5 min of ischaemic conditions followed by 15, 10, and 5 min of normal conditions, respectively. RESULTS: Without preconditioning, nerve-mediated responses were significantly and proportionally reduced by periods of ischaemic conditions lasting for 45, 60, and 90 min, but recovered fully after exposure to ischaemic conditions for 30 min. The recovery of the responses to EFS was significantly improved in preconditioned strips when the period of ischaemic conditions was 45 or 60 min. However, no significant differences were seen with preconditioning when the period of ischaemic conditions was 90 min. The recovery of responses to carbachol was much greater than for the responses to EFS, and no significant differences were found between control and preconditioned strips. CONCLUSIONS: It is suggested that in vivo short periods of transient ischaemia may be able to protect the guinea-pig bladder from the impairment associated with longer periods of ischaemia and reperfusion, which might happen in obstructed micturition. Our results also indicate that the phenomenon affects mainly the intrinsic nerves, which are more susceptible to ischaemic damage than the smooth muscle.     

Manipulations in glycogen metabolism and the failure to influence infarct size in the ischaemic rabbit heart

BACKGROUND AND OBJECTIVE: Myocardial ischaemic preconditioning is characterized by a reduction in the rate of glycolysis. Brief myocardial ischaemia also reduces the glycogen content of the heart. The first objective was to determine whether augmenting glucose oxidation by activation of the pyruvate dehydrogenase complex would prevent the infarct limitation of ischaemic preconditioning. The second part of the study evaluates whether glycogen depletion before ischaemia mimics the infarct-limiting effect of ischaemic preconditioning. METHODS: Dichloroacetate (300 + 150 mg kg(-1)), an activator of the pyruvate dehydrogenase complex, was administered intravenously in the anaesthetized open-chest rabbit. All animals underwent 45 min of regional ischaemia and 3 h of reperfusion. Ischaemic preconditiong was elicited by 5 min of coronary occlusion. Control rabbits, those with ischaemic preconditioning with no dichloroacetate, received a saline vehicle. An isolated perfused rabbit heart model was employed to test the second hypothesis. Hearts were depleted of glycogen by perfusing them with a substrate-free buffer. Infarction was assessed by triphenyl tetrazolium chloride and area at risk determined with fluorescent particles. RESULTS: (a) Pyruvate dehydrogenase complex activation experiments. Treatment with dichloroacetate alone did not alter infarct size (58 +/- 7% control vs. 60 +/- 5% dichloroacetate). Addition of dichloroacetate did not attenuate the infarct-limiting effect of ischaemic preconditioning as evidenced by a similar reduction in infarct size in the ischaemic preconditioning group (22 +/- 5%) and in the ischaemic preconditioning + dichloroacetate group (27 +/- 7%). (b) Glycogen depletion experiments. Compared with control hearts with a normal glycogen content (4.84 +/- 0.15 mg g(-1) wet weight), glycogen depleted and ischaemic preconditioning hearts had reduced glycogen content before ischaemia (2.15 +/- 0.26, 1.62 +/- 0.17 mg g(-1) wet weight, respectively; P < 0.01). Glycogen depletion did not reduce infarct size: 25.0 +/- 4.5% cf. 27.9 +/- 3.4% in the control group. However, ischaemic preconditioning resulted in a significant reduction of infarct size (11.5 +/- 2.3% vs. 27.9 +/- 3.4% control; P < 0.01). CONCLUSIONS: Augmentation of oxidative glycolysis by dichloroacetate in in situ rabbit hearts does not alter the effect of ischaemic preconditioning, and glycogen depletion in the isolated rabbit heart does not influence infarct size after subsequent coronary occlusion.     

外源性硫化氢在大鼠肾脏缺血再灌注损伤中的保护作用

目的 观察不同剂量外源性硫化氢(H2S)供体硫氢化钠对大鼠肾脏缺血再灌注损伤( IRI)的保护作用.方法 健康雄性Wistar大鼠28只随机分为4组,即假手术组( Sham)、肾缺血再灌注(IR)组、硫氢化钠(NaHS)高剂量组、硫氢化钠低剂量组.大鼠右肾切除后,以NaHS作为硫化氢的供体,NaHS高、低剂量组分别经左肾动脉插管,按照1.5 μmol/min、300 nmol/min的剂量连续15 min给药,假手术组及IR组给予同体积生理盐水.停药5 min 后,NaHS组和IR组用无损伤微动脉夹夹闭左侧肾蒂45 min后解除阻断,建立大鼠急性IRI模型,假手术组不夹闭左肾动脉,其他操作同模型组.于肾脏恢复血流24h时留取血和肾组织标本,检测血清尿素氮(BUN)、血肌酐(Scr);半定量分析肾脏病理损伤;检测肾组织H2S生成率;采用实时定量PCR法检测胱硫醚-β-合成酶(CBS)、胱硫醚-γ-裂解酶(CSE )mRNA表达.结果 与假手术组相比,IR组H2S生成率显著降低(P＜0.01);CBS、CSE mRNA表达显著下降(P＜0.01 );Scr、BUN显著升高(P＜0.01);肾脏病理表现为急性肾小管坏死,且最严重.与IR组相比,NaHS预处理组H2S生成率升高(P＜0.05);CBS、CSE mRNA表达升高(P＜0.01 );Scr、BUN降低(P＜0.01);病理损伤明显减轻.NaHS两个剂量组之间差异无统计学意义.结论 外源性H2S对大鼠IRI具有保护作用.     

Isoflurane does not mimic ischaemic preconditioning in decreasing hydroxyl radical production in the rabbit

Background. Reactive oxygen species are an important mediatorin isoflurane-induced myocardial preconditioning. However, hydroxylradicals are also released during reperfusion after regionalischaemia. The purpose of the present study was to test whetherischaemic preconditioning and isoflurane would influence theproduction of hydroxyl radicals during reperfusion. Methods. After i.v. administration of salicylate 100 mg kg^–1and a 30 min stabilization period, New Zealand White rabbitswere subjected to 40 min of regional myocardial ischaemia and2 h of reperfusion. Ischaemic preconditioning was elicited by5 min ischaemia followed by 10 min reperfusion (before the 40min ischaemia). In another group, isoflurane (2.1%) was administeredfor 30 min, followed by 15 min washout, before the long ischaemia.Area at risk and infarct size were assessed by blue dye injectionand tetrazolium chloride staining. We quantified the level ofOH-mediated conversion of salicylate to its dihydrobenzoatederivatives (2,3- and 2,5-DHBAs). Normalized values of the DHBAs(ng DHBA per mg salicylate) were calculated. Results. Mean (SE) infarct size was 57 (6)% of the risk areain the untreated controls. This was significantly smaller inthe ischaemic preconditioning and isoflurane groups: 22 (5)and 23 (6)% respectively. At 10 min of reperfusion, ischaemicpreconditioning limited the mean increase in 2,3-DHBA to 24%from baseline, compared with 81% in control and 74% in the isofluranegroup. Normalized 2,5-DHBA was maximally increased by 75% inthe untreated group, 4 min after reperfusion. Ischaemic preconditioningsignificantly inhibited this increase (24% increase from baseline,P<0.01). However, the increase observed in the isofluranegroup was not different from control (71%). Conclusions. As already known, ischaemic preconditioning andisoflurane markedly reduced infarct size. However, only ischaemicpreconditioning decreased postischaemic production of hydroxylradicals. These different effects suggest different protectivemechanisms at the cellular level.     

The role of oxygen-derived free radicals in peritoneal adhesion formation induced by ileal ischaemia/reperfusion

The effectiveness of superoxide dismutase (SOD), catalase (CAT), dimethyl sulphoxide (DMSO) and allopurinol in prevention of peritoneal adhesion formation induced by complete vascular obstruction and reperfusion of an ileal segment was investigated in rats. The ischaemic period was 30 min. Group A (n = 20) were controls, group B (n = 15) received SOD 15,000 U/kg i.v. and group C (n = 17) the same dose of CAT immediately before induction of ischaemia. In group D (n = 20) DMSO 20 mg/kg was given i.v. 5 min before ischaemia, and group E (n = 20) received allopurinol orally 50 mg/kg daily for 2 days and also 2 hours before ischaemia. Ten days later adhesions had developed in 80% of group A, 40% of group B, 47% of group C and 45% of groups D and E (p less than 0.05). The severity of the adhesions was significantly less in the pretreated groups than in the controls. Oxygen-derived free radicals may be pathogenetically important for such adhesion formation. Xanthine oxidase is the principal source of oxygen radicals after a 30-min period of complete regional intestinal ischaemia.     

The concept of anaesthetic-induced cardioprotection: mechanisms of action

The mechanisms by which ischaemia reperfusion injury can be influenced have been the subject of extensive research in the last decades. Early restoration of arterial blood flow and surgical measures to improve the ischaemic tolerance of the tissue are the main therapeutic options currently in clinical use. In experimental settings ischaemic preconditioning has been described as protecting the heart, but the practical relevance of interventions by ischaemic preconditioning is strongly limited to these experimental situations. However, ischaemia reperfusion of the heart routinely occurs in a variety of clinical situations, such as during transplantations, coronary artery bypass grafting or vascular surgery. Moreover, ischaemia reperfusion injury occurs without any surgical intervention as a transient myocardial ischaemia during a stressful anaesthetic induction. Besides ischaemic preconditioning, another form of preconditioning was discovered over 10 years ago: the anaesthetic-induced preconditioning. There is increasing evidence that anaesthetic agents can interact with the underlying pathomechanisms of ischaemia reperfusion injury and protect the myocardium by a preconditioning mechanism. Hence, the anaesthetist himself can substantially influence the critical situation of ischaemia reperfusion during the operation by choosing the right anaesthetic. A better understanding of the underlying mechanisms of anaesthetic-induced cardioprotection not only reflects an important increase in scientific knowledge but may also offer the new perspective of using different anaesthetics for targeted intraoperative myocardial protection. There are three time windows when a substance may interact with the ischaemia reperfusion injury process: (1) during ischaemia, (2) after ischaemia (i.e. during reperfusion), and (3) before ischaemia (preconditioning).     

Attenuation of reperfusion injury by renal ischaemic preconditioning: the role of nitric oxide

OBJECTIVE: To determine the effect on nitric oxide (NO) release and renal NO synthase (endothelial, eNOS and inducible, iNOS) activity of renal ischaemia-reperfusion (I/R) in vivo in an animal model, and to examine the possible involvement of NO in ischaemic preconditioning (IP) of the kidney. MATERIALS AND METHODS: In a right-nephrectomized rat model, 42 animals were randomized in four groups: controls; IP-only (4 min of ischaemia followed by 11 min of reperfusion, total of four cycles); renal warm ischaemia (45 min) and 6 h reperfusion; ischaemia (45 min) preceded by IP pretreatment. Serum NO metabolites were assayed 2 and 6 h after ischaemia or the control equivalent. NOS expression in the kidney was detected immuno-histochemically, and damage assessed morphologically in sections stained with haematoxylin and eosin. Kidney function was assessed by the levels of serum creatinine, urea and electrolytes. RESULTS: Compared with before ischaemia, the concentration of serum NO metabolites at 6 h was increased in the IP-only animals (P = 0. 016) and in the IP + I/R group (P = 0.002). There was greater eNOS expression in the IP-only group (P = 0.009) and in the IP + I/R group than in controls (P = 0.050). iNOS expression was greater in the IP-only animals than in the control group (P = 0.050). Histological assessment showed less evidence of cellular damage in IP + I/R animals than in the I/R-alone group (P = 0.020). Serum creatinine level was not significantly different between the IP-only group and the control. There were no differences after 2 h of reperfusion. CONCLUSION: Ischaemic preconditioning has a protective effect on renal structure and function, which may be produced by increased NO release arising from increased NOS expression by 6 h after reperfusion.     

Preoperative cooling and warming of the donor site increase survival of skin flaps by the mechanism of ischaemic preconditioning: an experimental study in rats.

Recent studies show that survival of skin flaps can be increased by ischaemic preconditioning with repeated cycles of ischaemia and reperfusion before prolonged ischaemia or raising of the flap. In this study three cycles of cooling and warming of rat dorsal skin were used to regulate skin blood flow and to induce three cycles of ischaemia and reperfusion. In 10 Sprague-Dawley rats three cycles of cooling (-18 degrees C ice pack) and warming (45 degrees C running water) were used to regulate skin blood flow before the flaps were raised. Caudally-based skin flaps 11 x 2 cm were then raised to the left of the dorsal midline and sutured back. In the control group (n = 9) the flap was raised and sutured back without any treatment. Viability was assessed after seven days and the survival area calculated with planimetry. Viability increased from a mean (SD) of 61 (6)% in the control group to 77 (7)% in the experimental group (p < 0.0001). This study shows that preoperative cooling and warming of the donor site can be used to increase survival of skin flaps. The probable explanation is ischaemic preconditioning although the biochemical mechanism is unclear.