丹星通络汤对脑缺血再灌注大鼠神经生长因子表达的影响

目的 观察丹星通络汤( DXTLD)治疗脑缺血再灌注大鼠后脑组织神经生长因子(NGF)的变化,探讨其对脑缺血再灌注损伤的保护机制. 方法 SD大鼠40只随机分为5组(n=8):假手术组、缺血再灌注组(模型组)、尼莫地平组、DXTLD预处理小剂量组、DXTLD预处理大剂量组.线栓法建立大鼠大脑中动脉缺血再灌注模型.应用免疫组织化学染色、灰度分析等方法检测缺血2h再灌注24 h后脑组织海马区NGF的表达. 结果 各治疗组缺血侧海马区的NGF表达显著增加,与模型组比较差异有统计学意义(P＜0.05或P＜0.01).结论 DXTLD通过上调脑缺血再灌注损伤后脑组织内NGF的表达,起到保护脑的作用.     

丹参对鼠脑缺血再灌注后白细胞介素-1β转化酶表达的影响

目的 研究丹参在脑缺血再灌注后对白细胞介素-1β转化酶(ICE)表达的影响及其神经保护作用.方法 利用沙土鼠前脑缺血再灌注模型,应用RT-PCR结合免疫组化的方法进行研究.结果 在脑缺血再灌注后1～4 d,皮层及海马可见ICE mRNA表达.免疫组化结果显示脑缺血再灌注后脑组织ICE阳性细胞数显著增多,而丹参组ICE表达显著低于缺血对照组,但仍显著高于假手术组(P＜0.01);丹参预防性干预组与丹参治疗性干预组相比,差异也有显著性意义(P＜0.01).结论 丹参可能通过调节ICE,进而发挥治疗脑缺血的作用.     

脑温对大脑灶性脑缺血再灌注损伤的影响

目的 研究预高温和缺血时轻度高温、亚低温对脑缺血再灌注损伤组织脂质过氧化和缺血脑组织病变的影响。方法 75只Wistar大鼠按不同脑温和缺血条件被随机分为生化组（5组，n=7)和病理组（5组，n=8),采用Nagasawa脑缺血模型，观察脑缺血再灌注损伤组织超氧化物歧化酶（SOD）、谷胱甘肽过氧化物酶（GSH－Px)、还原型谷胱甘肽（GSH）、丙二醛（MDA）及缺血脑组织病理变化。结果 轻度高温加重常温脑缺血组织SOD、GSH的降低和MDA的增高，使GSH－Px呈降低趋势，而亚低温相反；预高温对常温脑缺血各项指标影响不显。轻度高温组脑缺血病理损伤最重，亚低温和预高温有改善脑缺血损伤的作用。结论 高温加重而亚低温抑制脑血损伤，分别与其增加或减少内源性抗氧化酶消耗、降低或增强缺血脑组织清除氧自由基的能力有关；预高温对缺血脑组织有保护作用，未能肯定此作用与内源性抗氧化酶消耗减少和缺血脑组织清除氧自由基的能力增强有关。     

脑温对大鼠灶性脑缺血再灌注损伤的影响

目的　研究预高温和缺血时轻度高温、亚低温对脑缺血再灌注损伤组织脂质过氧化和缺血脑组织病变的影响。方法　 75只Wistar大鼠按不同脑温和缺血条件被随机分为生化组 (5组 ,n=7) 和病理组 (5组 ,n=8) ,采用Nagasawa脑缺血模型 ,观察脑缺血再灌注损伤组织超氧化物歧化酶 (SOD)、谷胱甘肽过氧化物酶 (GSH Px)、还原型谷胱甘肽 (GSH)、丙二醛 (MDA)及缺血脑组织病理变化。结果　轻度高温加重常温脑缺血组织SOD、GSH的降低和MDA的增高 ,使GSH Px呈降低趋势 ,而亚低温相反 ;预高温对常温脑缺血各项指标影响不显著。轻度高温组脑缺血病理损伤最重 ,亚低温和预高温有改善脑缺血损伤的作用。结论　高温加重而亚低温抑制脑缺血损伤 ,分别与其增加或减少内源性抗氧化酶消耗、降低或增强缺血脑组织清除氧自由基的能力有关 ;预高温对缺血脑组织有保护作用 ,未能肯定此作用与内源性抗氧化酶消耗减少和缺血脑组织清除氧自由基的能力增强有关     

二氮嗪对大鼠缺血再灌注损伤脑组织线粒体ATP酶活性的影响

目的 探讨线粒体ATP敏感性钾通道开放剂二氮嗪对大鼠局灶性脑缺血再灌注损伤脑组织线粒体ATP酶活性的影响.方法 采用改良线栓法建立大鼠局灶性大脑中动脉缺血再灌注损伤模型.将21只Wistar雄性大鼠随机分为假手术组(N组)、缺血再灌注组(IR组)、二氮嗪干预组(DZ组).缺血1 h再灌注24 h后留取标本,测定脑组织线粒体Na+-K+-ATP酶、Ca2+-Mg2+-ATP酶活性的变化.结果 与假手术组比较,缺血再灌注组Na+-K+-ATPase、Ca2+-Mg2+-ATP酶活性明显降低(P<0.05);二氮嗪干预组Na+-K+-ATP酶、Ca2+-Mg2+-ATP酶活性均较缺血再灌注组有不同程度的提高(P<0.05).结论 二氮嗪预处理能通过提高脑组织线粒体Na+-K+-ATP酶、Ca2+-Mg2+-ATP酶活性,减轻脑缺血再灌注损伤,保护神经元线粒体的功能,有效维持大脑能量代谢,发挥脑保护作用.     

党参对大鼠脑缺血再灌注损伤的保护作用

目的 研究党参(Codonopsis pilosula．)对大鼠脑缺血再灌注损伤的保护作用，并从改善能量代谢角度探讨其作用机制。方法 Wistar大鼠随机分为假手术组，缺血再灌注 生理盐水组，缺血再灌注 党参组，缺血再灌注 CoQ10组。其中缺血再灌注 生理盐水组、缺血再灌注 党参组、缺血再灌注 CoQ10组分别连续5d灌胃口服生理盐水、党参浸提液、CoQ10混悬液。采用阻断大鼠双侧颈总动脉和尾部放血，并重复缺血再灌注的脑缺血模型，分别于缺血后3，6，12h断头取脑，采用高效液相法测定脑组织中ATP含量、比色法测定Na^ ，K^ —ATPase活性。结果 生理盐水对照组中大鼠脑组织ATP含量、Na^ ，K^ —ATPase活性明显低于假手术组(P＜0．05)，党参组、CoQ10组中大鼠脑组织ATP含量、Na^ ，K^ —ATPase活性明显高于生理盐水对照组(P＜0．05)，且二者间无显著性差异。结论 党参可改善缺血再灌注脑细胞能量代谢，具有脑保护作用，作用效果与CoQ10相近。     

牛磺酸在大鼠缺血再灌注过程中对肝线粒体的保护作用

目的：观察缺血再灌注过程中线粒体的变化和牛磺酸的保护作用。方法：实验动物分为3组，假处理组（对照）组，阻断组，阻断＋牛磺酸组（保护组）。线粒体分离后测定呼吸功能，琥珀酸氧化酶，NADH氧经酶，细胞色素C氧化酶活性，MDA，GSH含量，钙，镁含量和游离钙的浓度。结果：肝缺血再灌注以后，线粒体呼吸功能和氧化磷酸化功能显著降低，引起线粒体脂质过氧化损伤，并可造成线粒体内GSH下降，使线粒体抗氧化系统活性下降；同时可引起线粒体内钙积聚，游离钙浓度明显升高以及镁的丢失。这些结果说明线粒体能量代谢障碍是缺血再灌注损伤的始动环节，而氧自由基是造成损伤的主要因素。牛磺酸对缺血再灌注损伤过程中线粒体损伤的各个环节均起保护作用。结论：研究表明牛磺酸作为自由基清除剂在体内可能具有非常重要的生理学作用。     

阿托伐他汀预处理和缺血预处理对大鼠脑缺血再灌注损伤的保护作用

目的观察阿托伐他汀预处理和缺血预处理对脑缺血再灌注损伤后的形态学改变,探寻更为有效的脑保护药物及防治方法。方法选择Wistar大鼠32只,随机分为4组。假手术组,缺血再灌注组,缺血预处理组,阿托伐他汀组,每组8只。采用线栓法建立大脑中动脉可逆性局灶性脑缺血再灌注模型,实验结束后取脑固定。经视交叉平面冠状切取脑组织厚2mm,包含新皮质(主要是额顶叶)、视前区及梨状区、纹状体、海马和丘脑。切成3μm的切片,行HE染色观察额顶叶皮质区及海马CAl区形态学变化。结果缺血再灌注组大脑额顶叶皮质区和海马CAl区核固缩性改变、细胞质嗜酸性改变较假手术组、缺血预处理组和阿托伐他汀组明显加重,差异有统计学意义(P<0.01)。结论脑缺血预处理和阿托伐他汀预处理对大鼠脑缺血再灌注损伤均有保护作用。     

肢体反复短暂缺血预处理在大鼠脑缺血再灌注损伤中的保护作用

目的 探讨肢体反复短暂缺血预处理(LIP)在大鼠脑缺血再灌注损伤中可能的脑保护机制.方法 随机将42只成年健康雄性Wistar大鼠分为7组,假手术组、脑缺血组、脑缺血再灌注组、预处理0 h组、预处理6 h组、预处理12 h组、预处理24 h组.采用线栓法制备大脑中动脉缺血及缺血再灌注模型,重复夹闭大鼠双侧股动脉4 次(每次10 min,间隔10 min) 作为LIP,采用生化方法测定各组脑组织中丙二醛(MDA)、超氧化物歧化酶(SOD)、三磷酸腺苷(ATP)酶的含量;HE染色观察大鼠脑组织的病理改变.结果 肢体反复短暂缺血预处理组可明显减少MDA的含量,升高SOD活性,增加ATP含量,尤以预处理0 h和6 h组为著,同其余预处理组及对照组相比差异有统计学意义(P<0.05).结论 肢体缺血预处理可提高脑缺血大鼠的SOD活性、降低MDA含量、促进ATP的生成,推知反复短暂的肢体缺血预处理对大鼠脑缺血再灌注损伤有保护作用,它可通过提高脑组织抗氧化酶活性、提高线粒体能量,抑制氧自由基产生及脂质过氧化反应来发挥作用.     

针刺联合川芎嗪处理对大鼠脑缺血再灌注损伤的影响

目的观察针刺联合川芎嗪处理对大鼠脑缺血再灌注损伤的影响。方法取健康SD大鼠18只,以线栓法制备大鼠脑缺血再灌注模型。随机分为假手术即正常对照组(A组,n=6)、缺血再灌注损伤对照组(B组,n=6)和针刺联合川芎嗪干预组(C组,n=6)。再灌注24 h后取脑,固定切片,染色。用大鼠行为学改变、病理形态学变化、凋亡细胞数三个指标对干预效果作出评价。结果成功复制大鼠鼠脑缺血再灌注损伤模型;针刺联合川芎嗪干预组效果显著,可明显改善缺血再灌注所致的神经元损伤。结论针刺联合川芎嗪处理能够有效抑制大鼠脑缺血再灌注损伤中神经细胞的凋亡,对大鼠有较好的脑保护作用。     

心肌缺血再灌注损伤亚细胞Ca~(2 )反常与ATP酶泵功能抑制

目的　研究心肌缺血再灌注损伤亚细胞Ca2 分布、含量及ATPase活性变化 ,探讨Ca2 反常与ATP酶泵功能抑制的关系。方法　采用离体心脏灌注模型 ,电子探针显微分析测定心肌缺血再灌注原位亚细胞Ca2 变化 ;电镜酶细胞化学及生化方法测定ATPase分布及活性变化。结果　心肌缺血 30min再灌注 30、6 0min肌浆网及肌膜Ca2 明显减少 (P <0 .0 1) ,而胞浆及线粒体内Ca2 明显增加 (P <0 .0 1)。再灌注肌浆网及肌膜Ca2 减少与胞浆及线粒体Ca2 增加呈负线性相关 ,r分别为- 0 .96 4和 - 0 .994,胞浆与线粒体Ca2 变化呈正线性相关 ,r为 0 .997。心肌缺血 30minATPase活性明显降低 ,缺血 30min再灌注 30及 6 0min进一步加重。结论　心肌缺血再灌注Ca2 超载发生在亚细胞水平 ,即亚细胞Ca2 的重新分布。ATPase泵功能抑制是心肌缺血再灌注亚细胞Ca2 紊乱的直接原因之一。     

Coronary artery ligation and reperfusion in rabbits made diabetic with alloxan

The biochemical and functional changes associated with ligation (40 min) of the left circumflex coronary artery and subsequent reperfusion (60 min) in the rabbit made diabetic with alloxan were studied and compared with those of control animals. Measurement of haemodynamic parameters revealed that both left ventricular pressure and mean arterial pressure were significantly (P less than 0.05) decreased after ligation and reperfusion in the diabetic animals compared with controls. Analysis of subcellular organelle enzyme markers from the ischaemic tissue revealed that sarcolemmal Na+,K+-ATPase, mitochondrial ATPase and sarcoplasmic reticulum ATPase activities were decreased after ligation to the same extent in the diabetic and control animals. However, upon reperfusion, the recovery of mitochondrial ATPase activity was significantly (P less than 0.05) less in the diabetic animals than in the controls. Ion measurements revealed a significant (P less than 0.05) depletion of Mg in diabetic hearts before ligation, and this was augmented during reperfusion. In contrast, a significantly (P less than 0.05) higher calcium accumulation was observed upon reperfusion in the hearts of diabetic animals. Similarly, both tissue ATP levels and the ability of the mitochondria to generate ATP were depressed to a greater degree in the diabetic animals. Our results indicate, therefore, a greater susceptibility of the diabetic myocardium to ischaemic/reperfusion injury which in the clinical situation would exacerbate the problems associated with atherosclerosis and possibly contribute to the high mortality from cardiovascular complications in diabetic patients.     

Melatonin protects against ischemic heart failure in rats

Ischemic injury, which occurs as a result of sympathetic hyperactivity, plays an important role in heart failure. Melatonin is thought to have antiatherogenic, antioxidant, and vasodilatory effects. In this study, we investigated whether melatonin protects against ischemic heart failure (HF). In Wistar albino rats, HF was induced by left anterior descending (LAD) coronary artery ligation and rats were treated with either vehicle or melatonin (10 mg/kg) for 4 weeks. At the end of this period, echocardiographic measurements were recorded and the rats were decapitated to obtain plasma and cardiac tissue samples. Lactate dehydrogenase, creatine kinase, aspartate aminotransferase, alanine aminotransferase, and lysosomal enzymes (β‐D‐glucuronidase, β‐galactosidase, β‐D‐N‐acetyl‐glucosaminidase, acid phosphatase, and cathepsin‐D) were studied in plasma samples, while malondialdehyde and glutathione levels and Na+, K+‐ATPase, caspase‐3 and myeloperoxidase activities were determined in the cardiac samples. Sarco/endoplasmic reticulum calcium ATPase (SERCA) and caveolin‐3 levels in cardiac tissues were evaluated using Western blot analyses. Furthermore, caveolin‐3 levels were also determined by histological analyses. In the vehicle‐treated HF group, cardiotoxicity resulted in decreased cardiac Na+, K+‐ATPase and SERCA activities, GSH contents and caveolin‐3 levels, while plasma LDH, CK, and lysosomal enzyme activities and cardiac MDA and Myeloperoxidase (MPO) activities were found to be increased. On the other hand, melatonin treatment reversed all the functional and biochemical changes. The present results demonstrate that Mel ameliorates ischemic heart failure in rats. These observations highlight that melatonin is a promising supplement for improving defense mechanisms in the heart against oxidative stress caused by heart failure.     

Melatonin suppresses cerebral edema caused by middle cerebral artery occlusion/reperfusion in rats assessed by magnetic resonance imaging

Melatonin, a pineal secretory product synthesized from tryptophan, has been found to be effective against neurotoxicity. The present study was aimed at demonstrating the effectiveness of melatonin in vivo in reducing ischemia-induced cerebral edema using magnetic resonance imaging (MRI). Rats were subjected to middle cerebral artery (MCA) occlusion/reperfusion surgery. Melatonin was administered twice (6.0 mg/kg, p.o.) just prior to 1 hr of MCA occlusion and 1 day after the surgery. T2-weighted multislice spin-echo images were acquired 1 day after the surgery. In the saline-treated control rats, increases in T2-weighted signals (water content) were clearly observed in the striatum and in the cerebral cortex. In the melatonin-treated group, total volume of edema was reduced by 51.6% compared with control group (P < 0.01). The protective effect of melatonin against edema was more clearly observed in the cerebral cortex (reduced by 59.8%, P < 0.01) than in the striatum (reduced by 34.2%, P < 0.05). Edema volume in a coronal slice was the greatest at the level of the bregma. Suppression of cerebral edema by melatonin was more effective posterior than anterior to the bregma. Melatonin appeared to reduce the volume of the edematous sites rather than to shift the signal intensity distribution. The present MRI study clearly demonstrates the effectiveness of melatonin against cerebral edema formation in ischemic animals in vivo, especially in the cerebral cortex. Melatonin may be highly useful in preventing cortical dysfunctions such as motor, sensory, memory, and psychological impairments associated with ischemic stroke.     

Melatonin prevents increases in neural nitric oxide and cyclic GMP production after transient brain ischemia and reperfusion in the Mongolian gerbil (Meriones Unguiculatus)

ABSTRACT: While nitric oxide (NO) has been implicated as a mediator of glutamate excitotoxicity after cerebral ischemia/reperfusion, melatonin has been reported to inhibit brain NO production by suppressing nitric oxide synthase. The purpose of the present studies was to determine the effect of exogenous melatonin administration on NO-induced changes during brain ischemia/reperfusion. Indicators of cerebral cortical and cerebellar NO production [nitrite/nitrate levels and cyclic guanosine monophosphate(cGMP)] were used to estimate neural changes after transient bilateral carotid artery ligation followed by reperfusion in adult Mongolian gerbils ( Meriones unguiculatus ). Results show for the first time that melatonin prevents the increases in NO and cGMP production after transient ischemia/reperfusion in frontal cerebral cortex and cerebellum of Mongolian gerbils. The inhibitory effect of melatonin on NO production and its ability to scavenge free radicals and the peroxynitrite anion may be responsible for the protective effect of melatonin on neuronal structures during transient ischemia followed by reperfusion.     

Melatonin provides neuroprotection by reducing oxidative stress and HSP70 expression during chronic cerebral hypoperfusion in ovariectomized rats

Abstract:  Oxidative stress is believed to contribute to functional and histopathologic disturbances associated with chronic cerebral hypoperfusion (CCH) in rats. Melatonin has protective effects against cerebral ischemia/reperfusion injury. This effect has mainly been attributed to its antioxidant properties. In the present study, we evaluate the effects of melatonin on chronic cerebral hypoperfused rats and examined its possible influence on oxidative stress, superoxide dismutase (SOD) activity, reduced glutathione (GSH) levels, and heat shock protein (HSP) 70 induction. CCH was induced by permanent bilateral common carotid artery occlusion in ovariectomized female rats. Extensive neuronal loss in the hippocampus at day 14 following CCH was observed. The ischemic changes were preceded by increases in malondialdehyde (MDA) concentration and HSP70 induction as well as reductions in GSH and SOD. Melatonin treatment restored the levels of MDA, SOD, GSH, and HSP70 induction as compared to the ischemic group. Histopathologic analysis confirmed the protective effect of melatonin against CCH-induced morphologic alterations. Taken together, our results document that melatonin provides neuroprotective effects in CCH by attenuating oxidative stress and stress protein expression in neurons. This suggests melatonin may be helpful for the treatment of vascular dementia and cerebrovascular insufficiency.     

曲美他嗪对大鼠缺血再灌注心肌线粒体的保护作用

目的探讨曲美他嗪对缺血再灌注损伤心肌线粒体的保护作用及其机制.方法将50只SD雄性大鼠随机分为假手术组、生理盐水组和曲美他嗪组(5mg/kg组及10mg/kg组)4组,假手术组只开胸,不结扎冠状动脉.余3组复制缺血再灌注损伤模型,缺血前分别静脉注射曲美他嗪(5或10mg/kg)及等量生理盐水,在缺血30min及再灌注40min时测定缺血再灌注损伤区心肌线粒体丙二醛、超氧化物歧化酶、谷胱甘肽、谷胱甘肽过氧化物酶及总钙浓度,并通过电镜观察心肌超微结构的改变.结果与假手术组比较,生理盐水组及曲美他嗪组线粒体中的丙二醛及总钙显著增高,超氧化物歧化酶、谷胱甘肽及谷胱甘肽过氧化物酶显著降低.与生理盐水组比较,曲美他嗪组的丙二醛及总钙水平显著降低,超氧化物歧化酶、谷胱甘肽及谷胱甘肽过氧化物酶显著增高.电镜观察显示曲美他嗪组线粒体损伤较生理盐水组明显减轻.结论以上提示曲美他嗪能减轻缺血再灌注心肌线粒体的脂质过氧化损伤,其机制可能是通过提高线粒体内谷胱甘肽含量及超氧化物歧化酶和谷胱甘肽过氧化物醇活性,以增强其抗氧化能力,并通过减轻线粒体内钙聚积在细胞水平提供心肌保护作用.     

Melatonin administration prevents cardiac and diaphragmatic mitochondrial oxidative damage in senescence-accelerated mice

Cardiac and diaphragmatic mitochondria from male SAMP8 (senescent) and SAMR1 (resistant) mice of 5 or 10 months of age were studied. Levels of lipid peroxidation (LPO), glutathione (GSH), GSH disulfide (GSSG), and GSH peroxidase and GSH reductase (GRd) activities were measured. In addition, the effect of chronic treatment with the antioxidant melatonin from 1 to 10 months of age was evaluated. Cardiac and diaphragmatic mitochondria show an age-dependent increase in LPO levels and a reduction in GSH:GSSG ratios. Chronic treatment with melatonin counteracted the age-dependent LPO increase and GSH:GSSG ratio reduction in these mitochondria. Melatonin also increased GRd activity, an effect that may account for the maintenance of the mitochondrial GSH pool. Total mitochondrial content of GSH increased after melatonin treatment. In general, the effects of age and melatonin treatment were similar in senescence-resistant mice (SAMR1) and SAMP8 cardiac and diaphragmatic mitochondria, suggesting that these mice strains display similar mitochondrial oxidative damage at the age of 10 months. The results also support the efficacy of long-term melatonin treatment in preventing the age-dependent mitochondrial oxidative stress.     

Melatonin reduces torsion-detorsion injury in rat ovary: biochemical and histopathologic evaluation

This experimental study was designed to determine the effects of melatonin on the levels of malondialdehyde (MDA), reduced glutathione (GSH), xanthine oxidase (XO) after adnexial torsion/detorsion (ischemia/reperfusion, I/R) of the ovaries of in rats. Forty adult albino rats were divided into five groups: sham operation, torsion, I/R plus saline, I/R plus melatonin and torsion plus melatonin. Rats in the sham-operated group underwent a surgical procedure similar to the other groups but the adnexa was not occluded. Rats in the torsion group were killed after adnexal torsion for 3 hr. Melatonin and saline were injected intraperitoneally (10 mg/kg) 30 min before detorsion to the I/R plus melatonin group and I/R plus saline group respectively. After 3 hr of ovarian detorsion, the rats were killed and ovaries were removed. Melatonin was injected intraperitoneally (10 mg/kg) 30 min before torsion to the torsion plus melatonin group. After 3 hr of ovarian torsion, the rats were killed and ovaries were harvested. The tissue levels of MDA, GSH and XO were measured. MDA and XO levels in the I/R plus saline group increased significantly when compared with torsion and sham-operated groups (P < 0.001). MDA and XO levels in the I/R plus melatonin group were lower than I/R plus saline and differences between the two groups were statistically significant (P < 0.001). GSH levels in the I/R plus saline group decreased significantly when compared with ischemia and sham-operated groups (P < 0.001). GSH levels in the I/R plus melatonin treated rats were significantly higher than I/R plus saline and ischemia groups (P < 0.001). The tissue levels of XO, MDA and GSH were similar between ischemia and ischemia plus melatonin groups. Morphologically, polymorphonuclear neutrophil infiltration and vascular dilatation were obvious in the I/R-damaged ovaries, and the changes also partially reversed by melatonin. This study demonstrates that melatonin protects the ovaries against oxidative damage associated with reperfusion following an ischemic insult.     

The relationship of regional coronary blood flow to mitochondrial function during reperfusion of the ischemic myocardium

The relationship of changes in regional coronary flow to the nature and degree of biochemical disturbances during occlusion of branches of the left anterior descending coronary artery and following reestablishment of flow was investigated in two groups of dogs: group I, moderate ischemia before reflow, and group II, severe ischemia prior to reflow. Regional coronary blood flow was determined before ligation, after 60 min of ischemia and after 15 min of reflow using labelled microspheres. Hearts made ischemic for 60 min but not reperfused served as controls. Groups I and II were distinguished by the following features. Group II showed a marked exacerbation of biochemical damage on reperfusion of the ischemic region (reduced levels of ATP, impairment of mitochondrial oxygen consumption and mitochondrial calcium binding). This was accompanied by significant subendocaridial hyperemia. Reperfusion in group I, on the otherhand, partially reversed these changes (increased level of ATP in the ischemic-reperfused region, improved mitochondrial oxygen consumption and calcium binding). Mitochondrial calcium uptake and oxidative phosphorylation (ADP/O ratio) were not affected in any group. These data illustrate that the degree of biochemical damage following reperfusion of the ischemic myocardium is determined by the degree of ischemia, and suggest that interference with ATP production by the mitochondria is not responsible for the damage.