Characterization of in vivo tissue redox status, oxygenation, and formation of reactive oxygen species in postischemic myocardium

The current study aims to characterize the alterations of in vivo tissue redox status, oxygenation, formation of reactive oxygen species (ROS), and their effects on the postischemic heart. Mouse heart was subjected to 30 min LAD occlusion, followed by 60 min reperfusion. In vivo myocardial redox status and oxygenation were measured with electron paramagnetic resonance (EPR). In vivo tissue NAD(P)H and formation of ROS were monitored with fluorometry. Tissue glutathione/glutathione disulfide (GSH/GSSG) levels were detected with high-performance liquid chromatography (HPLC). These experiments demonstrated that tissue reduction rate of nitroxide was increased 100% during ischemia and decreased 33% after reperfusion compared to the nonischemic tissue. There was an overshoot of tissue oxygenation after reperfusion. Tissue NAD(P)H levels were increased during and after ischemia. There was a burst formation of ROS at the beginning of reperfusion. Tissue GSH/GSSG level showed a 48% increase during ischemia and 29% decrease after reperfusion. In conclusion, the hypoxia during ischemia limited mitochondrial respiration and caused a shift of tissue redox status to a more reduced state. ROS generated at the beginning of reperfusion caused a shift of redox status to a more oxidized state, which may contribute to the postischemic myocardial injury.     

Relation between ischemic preconditioning and the duration of sustained ischemia.

It has been reported that repetitive brief periods of ischemia and reperfusion (ischemic preconditioning, IP) cause a significant reduction in the extent of myocardial necrosis or in the incidence of reperfusion arrhythmias in rat heart. However, recent reports have stated that IP effect is diminished or lost in the canine or bovine heart if ischemia (mostly regional) is sustained for 40 min or longer. The main objective of this study is to assess whether IP provides myocardial protection in prolonged sustained ischemia under the condition of global ischemia in isolated rabbit heart. The hearts were subjected to 10-60 min sustained ischemia (SI) followed by 60 min reperfusion with (IP heart) or without IP (ISCH heart). IP was induced by 4 cycles of 5 min global ischemia and 5 min reperfusion. Left ventricular function (LVF), extent of infarction (EI) and ultrastructural changes were examined. As a whole, the LVF began to recover on reperfusion but there was no significant difference in the functional parameters. However, extracellular Ca2+ concentration was lower in the ISCH hearts (p < 0.05) and the EI was significantly different between the hearts which had received 60 min SI (67% in the ISCH versus 32% in the IP heart, p < 0.01). Ultrastructural changes were homogeneous in the ISCH hearts and became irreversible in accordance with increase of the duration of ischemia, while these changes were heterogeneous and restricted in the IP heart. These results suggest that IP does not attenuate the postischemic dysfunction in prolonged ischemia but it can provide an infarct size-limiting effect and delay ultrastructural changes. This cardioprotective effect may be related to calcium homeostasis.     

Role of cannabinoid receptors in the regulation of cardiac contractility during ischemia/reperfusion

We studied the effect of selective ligands of cannabinoid (CB) receptors on contractility of isolated Langendorff-perfused rat heart under conditions of 45-min total ischemia and 30-min reperfusion. Perfusion with a solution containing selective CB receptor agonist HU-210 for 10 min before ischemia increased the severity of reperfusion contractile dysfunction. This drug decreased left ventricular developed pressure and maximum rates of contraction and relaxation, but had no effect on heart rate and end-diastolic pressure. The negative inotropic effect of the drug was transitory and disappeared after 5-min reperfusion. Pretreatment with selective CB1 receptor antagonist SR141716A and selective CB2 receptor antagonist SR144528 had no effect on heart rate and myocardial contractility during reperfusion. Our results indicate that stimulation of CB receptors can increase the degree of reperfusion-induced cardiac contractile dysfunction. However, endogenous cannabinoids are not involved in the development of myocardial contractile dysfunction during ischemia/reperfusion of the isolated heart. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 142, No. 11, pp. 500–504, November, 2006     

Protective effects of calmodulin antagonists (trifluoperazine and W-7) on hypothermic ischemic rat hearts

The cardioprotective effect of calmodulin antagonists, trifluoperazine (TFP) and N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide (W-7) was examined on the isolated rat heart exposed to hypothermic and ischemic conditions by measuring distribution of lysosomal enzymes in myocardial cells, and leakage of creatine kinase (CK) during reperfusion and postischemic recovery in myocardial systolic function. Experimental hearts were infused with 20 degrees C Krebs-Henseleit bicarbonate buffer (KHB) or KHB containing TFP or W-7 for 2min every 30min during hypothermic ischemia. After ischemia for 120min at 20 degrees C, rat hearts were reperfused at 37 degrees C for 30min. TFP and W-7 improved functional recovery and prevented CK release. In TFP treated hearts, leakage of lysosomal enzymes was reduced significantly, whereas stabilization of lysosomes by W-7 did not occur. These results suggest that calcium-calmodulin dependent enzymes may play an important role in the development of cellular damage of the myocardium during hypothermic ischemia, although levels of leakage of lysosomal enzymes may be unreliable predictors of functional recovery after hypothermic ischemia.     

Polymorphonuclear granulocytes induce myocardial dysfunction during ischemia and in later reperfusion of hearts exposed to low-flow ischemia

Polymorphonuclear granulocytes (PMNs) are known to contribute to reperfusion injury of the heart. However, whether PMNs compromise myocardial function of hearts exposed to a low-flow ischemia has not been determined. Moreover, not much is known about deleterious effects of PMNs at different times during ischemia and reperfusion. Isolated, working guinea pig hearts were subjected to 30 min of low-flow ischemia and reperfusion. Homologous PMNs were applied as 1-min boluses in the presence of thrombin during either ischemia or the first or fifth minute of reperfusion, and postischemic recovery of external heart work (REHW) and intracoronary PMN retention (PMNR) were quantified. In further experiments, the radical scavenger superoxide dismutase (SOD) was added. Compared with controls without PMNs (REHW, 92.4%), application of PMNs led to a significant loss of myocardial function, which was detected at all three examination times. Moreover, intracoronary PMNR increased significantly in comparison with that of controls with hearts not exposed to ischemia or reperfusion. On the other hand, addition of SOD significantly increased REHW. Intracoronary PMNR was not significantly changed by coapplication of SOD. We conclude that thrombin-stimulated PMNs applied at different times during ischemia and reperfusion significantly impaired cardiac function in hearts exposed to a low-flow ischemia.     

Preischemic selenium status as a major determinant of myocardial infarct size in vivo in rats

Prospective epidemiological studies have shown that the incidence of numerous cardiovascular pathologies is correlated with body selenium status. However, it remains unclear whether selenium status also influences the outcome of myocardial infarction. The aim of the present study was to test whether dietary selenium intake affects myocardial necrosis induced by transient regional ischemia in vivo in rats. For this purpose, male Wistar rats received either a high-selenium (High-Se: 1.5 mg of Se/kg) or a low-selenium (Low-Se: 0.05 mg of Se/kg) diet for 10 weeks. Animals were subjected to 30 min of myocardial ischemia induced by coronary artery ligation followed by 60 min of reperfusion. Pre- and postischemic blood samples were collected for glutathione (GSH and GSSG) determination and for glutathione peroxidase (GSH-Px) assessment. Our results show that high-selenium intake reduces myocardial infarct size (High-Se: 25.16 +/- 1.19% versus Low-Se: 36.51 +/- 4.14%, p < 0.05), preserves postischemic GSH/GSSG ratio (High-Se: 1.37 +/- 0.37 versus Low-Se: 0.47 +/- 0.10, p < 0.05), increases plasma GSH-Px activity, and improves postischemic mean arterial pressure. In conclusion, preischemic body selenium status is a major determinant of the outcome of myocardial ischemia in vivo in rats probably because it influences the cellular redox status.     

Activation of μ-opiate receptors as a factor of regulation of heart resistance to ischemia-reperfusion and oxidative stress

Intravenous injection of the selective μ-opiate receptor agonist DAMGO (0.1 mg/kg, 15 min before isolation of the heart) improved resistance of isolated perfused rat heart to ischemia (45 min) and reperfusion (60 min) damages.In vivo administration of DAMGO prevented reperfusion-induced damages to cardiomyocytes and decreased the content of conjugated dienes in the myocardium during ischemia-reperfusionin vitro. Furthermore, stimulation of μ-opiate receptors promoted recovery of myocardial contractility during reoxygenation, but had no effect on heart resistance to free radical-induced damages during perfusion of isolated heart with a solution containing Fe²⁺ and ascorbic acid.     

二氮嗪后处理对离体大鼠心功能及线粒体心磷脂的影响

目的:建立离体大鼠心肌缺血/再灌注损伤模型,观察二氮嗪(diazoxide,D)后处理对缺血/再灌注损伤离体大鼠心功能及线粒体心磷脂的影响,并探讨ATP敏感性钾通道在二氮嗪后处理心肌保护中的作用。方法:采用Langendorff装置建立离体大鼠心肌缺血/再灌注损伤模型,将SD大鼠随机分为对照组(control)、缺血再灌注模型组(I/R)、二氮嗪后处理组(I/R+D)、5-羟葵酸拮抗二氮嗪后处理组(I/R+5-HD+D),每组8只,均先灌注平衡20 min。Control组:灌注平衡后续灌70 min;I/R组:缺血前灌注4℃ST.Thomas停跳液,全心缺血40 min,再灌30 min;I/R+D组:全心缺血40 min,缺血后给予含二氮嗪(50μmol/L)的K-H液灌注5 min后,再灌25 min;I/R+5-HD+D组:二氮嗪后处理前给予含5-羟葵酸(100μmol/L)的K-H液灌注5 min,再灌20 min。观察各组续(再)灌注末心率、冠脉流出液量、心功能、心肌酶学及心肌线粒体心磷脂的变化。结果:各组续(再)灌注末比较,I/R组较control组及I/R+D组心率减慢、冠脉流出液量降低,心功能明显受损,心肌酶增加,心磷酯含量减少,但与I/R+5-HD+D无明显差异。结论:二氮嗪后处理通过增加线粒体心磷脂含量,减少心肌酶的释放,改善心脏功能,减轻心肌的再灌注损伤,产生心肌保护作用。5-羟葵酸能够完全阻断二氮嗪的心肌保护作用。     

基于压力相平面推导的τ和K在评价离体缺血/再灌注大鼠心脏左心室舒张功能中的作用

目的:应用分析和比较基于压力相平面(PPP)推导的心室等容舒张期时间常数)(和室腔僵硬度常数(K)在离体大鼠心脏缺血/再灌注过程中的变化,探讨其在评价左心室舒张功能异常中的价值。方法:采用SD大鼠心肌不同时程缺血/再灌注模型,分别计算出LVEDP、-(dp/dt)max、和K。同时,检测冠脉流出液中的乳酸脱氢酶(LDH),并进行心肌电镜观察。结果:在再灌注过程中,在各缺血组均明显高于空白对照组(P0.05),K在各缺血组均明显低于空白对照组(P0.05);而且,随着缺血时间延长,更高,K更低(P0.05)。除了缺血15min组,其余各组LDH含量在再灌注10min和20min时均高于空白对照组(P0.05);缺血45min组和缺血60min组LDH含量在再灌注10min和20min时均高于缺血30min组(P0.05)。随着缺血时间延长,心肌超微结构发生异常改变。结论:基于PPP推导的和K可以作为定量评价离体大鼠心脏缺血/再灌注过程中的左心室舒张功能的指标,还可以反映缺血/再灌注损伤的严重程度。     

Effect of Uridine Derivatives on Myocardial Stunning during Postischemic Reperfusion of Rat Heart

Uridine and uridine-5'-monophosphate prevent myocardial stunning during postischemic reperfusion of isolated rat heart. Uridine-5'-diphosphate does not prevent postischemic myocardial dysfunction, while uridine-5'-triphosphate aggravates it.     

氟烷和七氟醚对缺血再灌注心肌功能和氧自由基的影响

目的：研究１５肺泡最小浓度（ＭＡＣ）的氟烷和七氟醚对缺血再灌注心肌功能和氧自由基的影响。方法：应用离体大鼠心脏Ｌａｎｇｅｎｄｏｒｆ逆行灌注模型研究１５ＭＡＣ的氟烷、七氟醚对心肌缺血前后心功能的影响,测定缺血前、缺血１０ｍｉｎ、复灌３０ｍｉｎ３个不同时间的心肌超氧化物歧化酶（ＳＯＤ）活性和丙二醛（ＭＤＡ）含量。结果：七氟醚不同程度地抑制心肌收缩功能。缺血１０ｍｉｎ时,七氟醚组ＳＯＤ酶活性明显下降,ＭＤＡ含量显著升高。缺血２５ｍｉｎ复灌３０ｍｉｎ后,二药均能促进心肌功能和ＳＯＤ酶活性恢复,抑制ＭＤＡ生成,其中七氟醚的作用较为明显。结论：二药对缺血再灌注心肌具有一定的保护作用,七氟醚优于氟烷。     

Changes in catecholamine, angiotensin converting enzyme and adenosine triphosphatase in ischemic preconditioning rat hearts

Changes in catecholamine ,angiotensin converting enzy me and adenosine triphosphatase in ischemic preconditioning rat hearts     

心肌缺血—再灌注损伤与心肌去甲肾上腺素的释放

家兔急性开胸实验,结扎冠状动脉左室支35分钟后,去除结扎(再灌注)10分钟,发现心脏功能较单纯结扎组明显降低,再灌注区心肌去甲肾上腺素(NA)含量显著降低,同时伴有组织Ca~( )含量显著升高。测定血钙和组织含水量结果提示,再灌注后心肌Ca~( )含量的升高系由Ca~( )在细胞内的堆积所致。再灌注损伤可能与再灌注过程中心肌组织内源性儿茶酚胺大量释放有关。     

Nitric oxide and peroxynitrite in postischemic myocardium

Alterations in the production of nitric oxide (NO.) are a critical factor in the injury that occurs in ischemic and reperfused myocardium; however, controversy remains regarding the alterations in NO. that occur and how these alterations cause tissue injury. As superoxide generation occurs during the early period of reperfusion, the cytotoxic oxidant peroxynitrite (ONOO-) could be formed; however, questions remain regarding ONOO- formation and its role in postischemic injury. Electron paramagnetic resonance spin trapping studies, using the NO. trap Fe(2+)-N-methyl-D-glucamine dithiocarbamate (Fe-MGD), and chemiluminescence studies, using the enhancer luminol, have been performed to measure the magnitude and time course of NO. and ONOO- formation in the normal and postischemic heart. Isolated rat hearts were subjected to control perfusion, or ischemia followed by reperfusion in the presence of Fe-MGD with electron paramagnetic resonance measurements performed on the effluent from these hearts. Whereas only trace signals were present prior to ischemia, prominent NO. adduct signals were seen during the first 2 min of reflow. The reperfusion associated increase in these NO. signals was abolished by nitric oxide synthase inhibition. In hearts perfused with luminol to detect ONOO- formation, a similar marked increase was seen during the first 2 min of reperfusion that was blocked by nitric oxide synthase inhibitors and by superoxide dismutase. Either NG-nitro-L-arginine methyl ester or superoxide dismutase treatment resulted in more than twofold higher recovery of contractile function than in untreated hearts. Immunohistology studies demonstrated that the ONOO(-)-mediated nitration product nitrotyrosine was formed in postischemic hearts, but not in normally perfused controls. Thus, NO. formation is increased during the early period of reperfusion and reacts with superoxide to form ONOO-, which results in protein nitration and myocardial injury.     

Activation of μ-opiate receptors as a factor of regulation of heart resistance to ischemia-reperfusion and oxidative stress

Intravenous injection of the selective μ-opiate receptor agonist DAMGO (0.1 mg/kg, 15 min before isolation of the heart) improved resistance of isolated perfused rat heart to ischemia (45 min) and reperfusion (60 min) damages.In vivo administration of DAMGO prevented reperfusion-induced damages to cardiomyocytes and decreased the content of conjugated dienes in the myocardium during ischemia-reperfusionin vitro. Furthermore, stimulation of μ-opiate receptors promoted recovery of myocardial contractility during reoxygenation, but had no effect on heart resistance to free radical-induced damages during perfusion of isolated heart with a solution containing Fe²⁺ and ascorbic acid. Translated fromByulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 130, No. 8, pp. 163–167, August, 2000     

甘氨酰谷氨酰胺在大鼠离体心脏缺血/再灌注损伤中的保护作用研究

目的： 研究甘氨酰谷氨酰胺对缺血再灌注大鼠离体心脏的保护作用。方法：应用Langendorff离体心脏灌注系统建立心肌缺血再灌注模型。30只SD雄性大鼠随机分为正常对照组(control)、甘氨酰谷氨酰胺对照组(Gly-Gln)、缺血再灌注组(I/R)、缺血/再灌注+甘氨酰谷氨酰胺组(I/R+ Gly-Gln)。I/R组及I/R+ Gly-Gln组分别灌注30 min后,全心停灌20 min,再灌注40 min,I/R+ Gly-Gln组于再灌注时在灌流液中加入Gly-Gln;正常对照组连续灌流90 min,Gly-Gln对照组灌流液中加入Gly-Gln。记录各组灌注时,左室舒张末压(LVEDP)、左室发展压(LVDP)、左室压力最大变化速率(±dp/dtmax)、心率(HR)及心肌细胞单相动作电位(MAP);同时在相应的时点分别测定冠脉流出液中的乳酸脱氢酶（LDH)、肌酸激酶(CK)活性。结果：离体大鼠心脏缺血20min,再灌注40 min,导致严重的心功能抑制,表现为LVEDP升高,LVDP、±dp/dtmax降低;再灌注液中加入Gly-Gln后,LVEDP降低,LVDP、±dp/dtmax明显升高（P<0.01)。I/R+ Gly-Gln组冠脉流出液中LDH、CK活性明显低于I/R组(均P<0.01)。结论： Gly-Gln能有效减轻缺血再灌注引起的左室功能下降,减少心肌细胞LDH、CK的释出,表明Gly-Gln对缺血再灌注损伤的大鼠离体心脏具有保护作用。     

Ischemia/reperfusion-induced changes in intracellular free Ca2+ levels in rat skeletal muscle fibers – an in vivo study

Accumulation of intracellular free calcium (Ca2+i) may play an essential role in the ischemia/reperfusion injury of skeletal muscle. Although it has been shown that Ca2+i levels significantly increase during ischemia/reperfusion, it is still a matter of debate whether Ca2+i increases during ischemia alone. It was the aim of this study to monitor the in vivo Ca2+i levels in the rat spinotrapezius muscle during ischemia of varying duration and reperfusion, using a ratiometric fluorescence technique, and to investigate the relationship between the postischemic flow patterns and Ca2+i, if any. The muscle was loaded with Indo-1/AM and imaged by a cooled digital camera. Pre- and postischemic tissue perfusion was assessed by means of an analogue camera. Our results show that short-term ischemia (5, 15 and 30 min) and subsequent reperfusion (60 min) does not alter Ca2+i homeostasis and that tissue perfusion promptly recovers after the insult. One or two hours of ischemia resulted in changes in Ca2+i levels, varying from preparation to preparation; increases in some and no changes in others. In these preparations three distinct flow patterns - normal, compromised and no-reflow - could be distinguished during the 60-min reperfusion. Our main conclusion is that in skeletal muscle Ca2+i levels may increase, the increase probably depending on the muscle fiber type exposed.     

挥发性麻醉药对大鼠离体心脏缺血再灌注损伤的影响

目的： 研究挥发性麻醉药对大鼠离体心脏缺血再灌注损伤的影响。方法： SD大鼠136只，随机分为17组，每组8只。采用Langendorff离体大鼠心脏模型。按给药方式分为6大组：假手术组（含1亚组）：自然灌流85 min;对照组（含4亚组）：平衡15 min为1亚组，平衡后续灌15 min为1亚组，平衡续灌后缺血10 min为1亚组，平衡续灌缺血25 min后复灌30 min为1亚组;氟烷组（含3亚组）：平衡15 min后，灌注含1.5 MAC氟烷灌注液15 min为1亚组，平衡续灌含药液后缺血10 min为1亚组，平衡续灌缺血25 min复灌含1.5 MAC氟烷的灌注液30 min为1亚组;1.5 MAC的恩氟烷、异氟烷、七氟烷大组，各大组包括3亚组，处理同氟烷组。记录各组心脏在平衡15 min、给药后(或续灌15 min)、复灌30min的左室收缩压(LVSP)、左室舒张末压(LVEDP)、左室发展压(LVDP)、左室压力升高或降低最大速率(±dp/dtmax)、心率（HR）、冠脉流量（CF）。实验结束后测定心肌超氧化物歧化酶（SOD）活性、心肌丙二醛（MDA）含量、高能磷酸盐（ATP）含量、Na＋-K＋-ATP酶、Ca2＋-ATP酶活性。结果： （1）恩氟烷、异氟烷、七氟烷组在给药后CF高于对照组（P<0.05）；各用药组在给药后LVDP、±dp/dtmax低于对照组（P<0.01）、而LVEDP高于对照组（P<0.05）；复灌30 min各用药组LVDP、±dp/dtmax高于对照组（P<0.01）。氟烷、异氟烷组在给药后和复灌30 min的HR低于对照组（P<0.05或P<0.01）。（2）各用药组在缺血前、缺血期和复灌30 min的心肌ATP含量高于及复灌30 min SOD活性高于对照组，MDA含量低于对照组（P<0.05或P<0.01）。（3）氟烷、恩氟烷、异氟烷组在缺血前Ca2＋-ATP酶活性低于对照组、各用药组在缺血期和复灌30 min此酶活性高于对照组（P<0.05或P<0.01）。（4）在复灌30min，氟烷组的Na＋-K＋-ATP酶活性高于对照组和其它3用药组（P<0.05或P<0.01）。结论： 挥发性麻醉药可抑制心肌收缩功能，对缺血再灌注心肌有保护作用。缺血再灌注后，能明显促进心肌功能与代谢的恢复，而且能提高CF、心肌Ca2＋-ATP酶及Na＋-K＋-ATP酶活性。     

Oxidized and ubiquitinated proteins may predict recovery of postischemic cardiac function: essential role of the proteasome

This study examined the hypothesis that postischemic levels of oxidized and/or ubiquitinated proteins may be predictive of functional recovery as they may be indicative of activity of the 20S and/or 26S proteasomes, respectively. Subjecting isolated rat hearts to 15 min of ischemia had no effect on 20S- and 26S-proteasome activities; however, both were significantly (p < 0.05) decreased by 70% and 54%, respectively, following 30 min of ischemia and 60 min of reperfusion, changes associated with increased levels of protein carbonyls and ubiquitinated proteins. Preischemic treatment of hearts with the proteasome inhibitor, MG132, resulted in dose-dependent decreases (p < 0.05) in recovery of postischemic function [MG132 (microM), heart rate x pressure product: 0, 11,158 +/- 2,423; 6, 11,400 +/- 3,009; 12, 5,513 +/- 2,225; 25, 2,325 +/- 992] and increased accumulation of ubiquitinated proteins. Preconditioning with repetitive ischemia (IP) or preischemic treatment with nicorandil (Nic) resulted in a significant increase in postischemic 20S-proteasome activity after 60 min of reperfusion (control, 95 +/- 4; IP, 301 +/- 65; Nic, 242 +/- 61 fluorescence units). Only Nic had similar effects on 26S-proteasome activity. These results support the conclusion that a correlation exists between eventual recovery of postischemic function and levels of oxidized and/or ubiquitinated proteins, a phenomenon that may be dependent on activity of the 20S and 26S proteasomes.     

缝隙连接脱耦联剂庚醇对大鼠缺血-再灌注损伤心肌的保护作用

目的：在整体大鼠心脏缺血-再灌注损伤模型上研究庚醇的心肌保护作用，并在离体缺氧心脏模型上观察庚醇对电耦联参数的影响。方法：在体大鼠实验模型，结扎冠状动脉左前降支30 min和复灌2 h，观察不同剂量的庚醇（0.03、0.06、0.30和0.60 mg/kg）的作用；离体大鼠实验模型，全心停灌70 min，应用四电极法观察不同浓度的庚醇（0.05、0.10、0.50和1.00 mmol/L）对缺氧期间心肌整体阻抗和电脱耦联参数的影响。结果：庚醇对在体大鼠缺血-再灌注损伤心肌具有减少心律失常发生和缩小心肌梗死面积的作用；各浓度庚醇（0.05-1.00 mmol/L）均明显延迟心肌缺氧期间电脱耦联时间和平台时间，降低电脱耦联最大速率。结论：适度剂量的庚醇对在体缺血-再灌注损伤心肌有保护作用，其作用可能与其引起的电脱耦联延迟有关。