血管钠肽抑制异丙肾上腺素增强的大鼠心肌细胞钙瞬变

采用光谱荧光法研究血管钠肽(vasonatrin peptide,VNP)对心肌细胞内钙瞬变的作用及其机制,观察钠尿肽鸟苷酸环化酶(guanylate cyclase,GC)受体的特异性阻断剂(HS-142-1)、8-溴-环磷酸鸟苷(8-Br-cGMP)和镁蓝(methylene blue,MB)对心肌细胞内钙瞬变的影响。结果显示,异丙肾上腺素(isoproterenol,Iso)(10~(-10)～10~(-6)mol/L)可剂量依赖性地引起心肌细胞内钙瞬变增强,相对于对照组分别增强(13±8)%(P>0.05)、(26±13)%(P<0.05)、(66±10)%(P<0.01)、(150±10)%(P<0.01)和(300±25)%(P<0.01)。此效应可被β肾上腺素受体阻断剂普萘洛尔(10~(-6)mol/L)所阻断。VNP(10~(-10)～10~(-6)mol/L)可剂量依赖性地抑制Iso(10~(-8)mol/L)引起的心肌细胞内钙瞬变幅值的升高,相对于Iso(10~(-8)mol/L)分别减弱(99±3)%(P>0.05)、(96±2)%(P<0.05)、(84±6)%(P<0.01)、(66±3)%(P<0.01)和(62±3)%(P<0.01)。8-Br-cGMP(10~(-7)～10~(-3)mol/L)也可剂量依赖性地抑制Iso(10~(-8)mol/L)引起心肌细胞内钙瞬变的增强。HS-142-1(2×10~(-5)mol/L)使VNP的作用几乎完全消失。MB是GC的抑制剂,10~(-5)mol/L MB不但使VNP的作用完全消失,而且增强Iso对心肌细胞内钙瞬变的效应。VNP和HS-142-1本身对心肌细胞内钙瞬变无显著影响。而MB使心     

一氧化氮供体对过氧化氢引起的心肌细胞损伤的保护作用

关于一氧化氮(NO)对心肌细胞是否具有保护作用目前尚存在争议,为探讨NO对过氧化氢(H2O2)引起的心肌细胞损伤是否具有保护作用及其可能的机制,实验将体外培养的新生大鼠心肌细胞分为3组(1)阴性对照组(Normal组);(2)H2O2组H2O2(0.1mmol/L)与心肌细胞共育4h;(3)S-亚硝基-N-乙酰青霉胺(SNAP)+H2O2组NO供体SNAP(0.5mmol/L)处理心肌细胞10min后,加入H2O2与心肌细胞共育4 h.用流式细胞术检测心肌细胞凋亡率,心肌细胞损伤程度以心肌细胞存活率和乳酸脱氢酶(lactate dehydrogenase,LDH)活性来表示,同时检测心肌细胞超氧化物歧化酶(superoxide dismutase,SOD)活性和丙二醛(MDA)含量.通过激光共聚焦显微术检测在不同处理条件下心肌细胞胞内钙的变化.结果表明,正常心肌细胞LDH活性和细胞存活率分别为631.4±75.6 U/L和93.1±6.2%,细胞凋亡率为0;H2O2处理细胞后可使细胞LDH活性显著增高(1580.5±186.7 U/L,P＜0.01),细胞存活率明显下降(58.3±7.6%,P＜0.01),流式细胞仪检测到大量心肌细胞凋亡,凋亡率为26.4±5.7%;SOD活性较正常细胞19.67±0.85 NU/ml显著下降,为14.73±1.68 NU/m(P＜0.01),MDA含量较正常细胞6.95±0.83μmol/L显著增高,为15.35±3.49μmol/L(P＜0.01).SNAP预处理细胞可显著提高心肌细胞存活率(79.7±9.3%,P＜0.01),降低LDH活性和细胞凋亡率(分别为957.8±110.9 U/L和9.1±3.3%,P＜0.01);并提高细胞抗氧化能力,表现为较H2O2处理组的SOD活性增高(21.36±3.11 NU/ml,P＜0.01),MDA含量下降(9.12±1.47 μmol/L,P＜0.01).激光共聚焦显微镜检测结果表明,H2O2可升高细胞内钙,而SNAP则可降低细胞内钙,SNAP预处理细胞后可取消H2O2升高细胞内钙的作用.上述结果提示,NO供体SNAP可对抗H2O2对心肌细胞的损伤,其机制与提高心肌细胞抗氧化损伤能力和对抗H2O2引起的细胞内钙超载有关.     

大鼠和黄鼠心肌细胞钙瞬变记录和钙移除机制分析

用共聚焦显微术在不同温度下记录非冬眠动物大鼠和冬眠动物黄鼠心肌细胞钙瞬变,并分析钙移除速率.结果表明:大鼠细胞钙瞬变舒期水平随降温显著升高,黄鼠基本不变;相同温度下,黄鼠钙瞬变时程较短,钙移除速率较快.CPA(cyclopiazoni cacid)的药理作用显示肌质网是细胞钙移除的主要机制,黄鼠肌质网摄钙速率较大鼠快.肯定了肌质网在冬眠动物心肌细胞耐受低温适应中的关键地位,否定了钠钙交换发挥重要作用的观点,提出了改善非冬眠动物心肌低温耐受性的可能性.     

钙与心肌缺血再灌注诱发的心肌细胞凋亡

细胞凋亡 ( Apoptosis)是最基本的细胞死亡过程 ,是一种普遍存在的生命现象。细胞凋亡与细胞增殖的动态平衡是多细胞生物维持其结构稳定及内环境动态平衡和生长发育所必有的最基本的生物学现象。不适当的细胞凋亡所致的凋亡失调性疾病( Disease of Disregulated Apoptosis,DDA)正受到人们的关注 [1]。这些疾病包括细胞凋亡减弱性疾病和细胞凋亡增强性疾病 ,前者如肿瘤、自身免疫性疾病、病毒感染及慢性炎症性疾病。后者包括神经元退行性疾病、造血衰竭性疾病、缺血性损伤等。在心血管系统疾病中 ,心肌梗塞、心肌缺血再灌注损伤、心肌炎、…     

心肌细胞钙瞬变和细胞收缩的激光共聚焦成像研究

目的：游离钙离子参与机体的多种重要生理功能。本研究着重探讨如何利用激光共聚焦显微镜线扫描成像技术同时记录正常情况下心肌细胞的钙瞬变以及由此引起的细胞收缩过程。方法与结果：本研究以分离的心室肌细胞为对象,通过局部场刺激诱发细胞的钙瞬变和收缩,同时配合使用激光共聚焦显微镜成像系统,以线扫描方式记录实验结果。结果表明,钙瞬变先于细胞收缩发生(约早31ms),而收缩最大处远落后于钙瞬变峰值发生处(约慢346ms)。结论：激光共聚焦显微镜线扫描成像技术具有较好的时问分辨率和空间分辨率,其实验结果直观、明确、可靠,是较理想的研究钙瞬变和细胞收缩的光学记录方法。     

大鼠心肌细胞凋亡的保护作用

为探讨p53上调凋亡调制物(p53 up-regulated modulator of apoptosis, PUMA)在大鼠心肌细胞缺氧/复氧（hypoxia/reoxygenatio, H/R）损伤中的作用,本 研究将靶向PUMA的siRNA（si-PUMA）转染大鼠心肌细胞以建立PUMA沉默表达模型,观察其对心肌细胞H/R损伤的影响.RT-PCR和Western印迹结果表明,最适转染浓度50 nmol/L si-PUMA能靶向抑制H/R损伤心肌细胞的PUMA表达;MTT法检测心肌细胞存活率及培养基乳酸脱氢酶（lactate dehydrogenase, LDH）活性测定结果发现,si-PUMA 组细胞存活率较H/R 6 h模型组明显提高,培养液中LDH活性显著降低（P<0.01）;分光光度法及Annexin V-FITC/PI联合染色流式细胞凋亡检测结果显示,si-PUMA组caspase-3活性较H/R 6h组明显下调,细胞凋亡率明显降低（P <0.01）;RT-PCR结果 提示,与H/R 6 h组相比,si-PUMA组Bax及Bcl-2表达分别出现显著下调及上调（P <0.05）.以上结果表明,靶向PUMA的siRNA转染能明显增强心肌细胞耐受H/R损伤的能力,对心肌细胞具有较好的保护作用;PUMA介导H/R诱导的心肌细胞凋亡,是心肌缺血/再灌注损伤基因治疗的一个潜在靶点.     

甲状腺素对大鼠心肌细胞收缩功能及钙瞬变的影响

目的：研究甲状腺素对单个心肌细胞收缩功能及钙瞬变的影响。方法：SD大鼠60只随机分为对照组（30只）、甲状腺素组（30只）。通过给予甲状腺素喂养后,测量血流动力学指标,随后分离单个心室细胞,采用可视化动缘探测系统同步检测大鼠心肌细胞收缩和钙瞬变的变化并与对照组比较。结果：（1）甲状腺素治疗组左室收缩压（LVSP）和最大缩短和复长速率（&#177;dp／dtmax）较对照组明显提高（P〈0．05）,左室舒张末压（LVEDP）较对照组明显下降（P〈0．05）。（2）甲状腺素治疗组单个心肌细胞收缩功能指标最大收缩幅度（PTA）、最大缩短和复长速率（&#177;dL／dtmax）较对照组明显增加（P〈0．05）,钙瞬变指标fura-2荧光强度变化（△FFI）明显增强、Ca2＋离子达峰值时程（TTPCa）、舒张期Ca2＋减少50％时程（T50DCa）较对照组明显缩短（P〈0．05）。结论：甲状腺素可改善大鼠心脏功能并增强单个心肌细胞的收缩功能及钙瞬变幅度,在单细胞水平上为探讨甲状腺素治疗慢性心衰的发生机制提供了实验依据。     

胞外镁离子对SD成年大鼠心肌细胞胞内钙信号的影响

目的：研究胞外不同浓度的镁离子对SD成年大鼠心肌细胞钙瞬变的影响。方法：采用激光共聚焦显微镜系统同步配合阈上电刺激探测心肌细胞钙瞬变。结果：胞外低浓度的镁离子（0 mmol /L,0.5 mmol /L; 正常镁离子浓度为1 mmol/L）可以升高钙瞬变的峰值（P〈0.05）,但不影响钙瞬变的持续时间（以钙瞬变的半高宽表示）（P〉0.05）;胞外高浓度的镁离子（2.5 mmol /L,5 mmol /L,10 mmol /L）均可抑制钙瞬变的峰值（P〈0.05）;其中5 mmol/L和10 mmol/L的胞外镁还能延长钙瞬变的持续时间（P〈0.05）。结论：正常情况下镁对心肌细胞钙瞬变有抑制作用。     

心肌细胞的钙致钙释放

心肌细胞兴奋－收缩偶联由胞内钙变中介和调控。去极化进进入细胞的少量钙通过钙下释放（ＣＩＣＲ）过程发肌质多（ＳＲ）释放更多的钙,使胞浆钙浓度升高,导致收缩近年来证明,ＳＲ钙放呈梯级特征,提出了局部控制模型,以解释这种现象。钙火花的发现,直观地证硒钙释放单位的存在,进一步支持了局部控制模型。此外,钙释放通道的适应现象,可能是ＣＩＣＲ这一正反馈过程的负调节机制。     

间歇运动对心梗大鼠梗死周边区单个心肌细胞钙瞬变和收缩功能的影响

目的:探讨间歇运动对心梗大鼠缺血心肌细胞钙瞬变和收缩功能改变的影响。方法:3月龄SD雄性大鼠24只,适应性喂养1周后随机分为假手术组(S)、心梗组(MI)、心梗+运动组(ME),每组8只。MI组结扎左冠状动脉前降支制备心梗模型;S组只穿线不结扎;ME组术后一周开始间歇训练,运动方式为1周适应性运动(10 m/min×30 min/d),然后先以10 m/min×10 min,再以15 m/min×6 min和25 m/min×4 min依次交替运功,60 min/d,每周5 d连续8周。训练结束后次日,腹腔麻醉并分离心肌细胞。采用单细胞可视化动缘探测系统(IonOptix)测定[Ca^2+]i amplitude、[Ca^2]+i荧光比率(Ratio)、Departure velocity、TTP、TTP50%、TTB50%、Return velocity以及Ratio amplitude等钙瞬变指标和±dl/dtmax、SL、PTA、SL shortening%等心肌细胞收缩指标。结果:与S组相比,MI组[Ca^2+]i amplitude、[Ca^2+]i Ratio amplitude,Departure velocity和Return velocity均显著下降(P<0.01),TTB50%、TTP和TTP50%均显著增加(P<0.01),心肌细胞肌节SL Shortening%、PTA、±dl/dtmax均显著减少(P<0.01);与MI组相比,ME组Ratio amplitude、[Ca^2+]i amplitude、Return velocity和Departure velocity均显著提高(P<0.01),TTB50%、TTP和TTP50%均显著缩短(P<0.01,P<0.05),心肌细胞肌节SL Shortening%、PTA、±dl/dtmax均显著提高(P<0.01,P<0.05)。结论:间歇运动可同步改善MI大鼠梗死周边区心肌活细胞的钙瞬变异常和心肌细胞的收缩功能。     

活性氧自由基对心肌细胞损伤效应研究

为探讨活性氧自由基对心肌细胞的影响 ,采用胰蛋白酶酶消化法分离SD乳鼠心肌细胞 ,培养于适当的条件并观察其形态学和生理学方面的特征 ;加入H_{2O2 活性氧刺激心肌细胞 ,模拟氧自由基损伤心肌细胞方式 ,构建心肌细胞缺血再灌注损伤的模型并了解H2O2 对心肌细胞的损伤作用。结果表明胰蛋白酶消化分离的心肌细胞能够在体外完好生长 ,并能够在一段时间内维持其原有的生理特性 ;MTT检测结果和形态学观察结果表明H2O2 对心肌细胞的损伤与其浓度和作用时间呈正比关系 ,TUNEL和DNA凝胶电泳分析结果显示 ,H2O2 在心肌细胞中的积累是造成细胞凋亡的主要因素之一。}     

Sirt3对过氧化氢诱导的骨髓间充质干细胞凋亡的保护作用

目的:通过调控骨髓间充质干细胞(mesenchymal stem cells,MSCs)中的Sirtuin-3(Sirt3)蛋白的表达水平,阐明Sirt3对过氧化氢(H2O2)诱导MSCs凋亡的保护作用及其机制。方法:将大鼠MSCs分为正常对照组、H2O2刺激组、H2O2+Sirt3转染组、H2O2+Sirt3 si RNA转染组。利用Western blot法检测Sirt3及cyclophilin d蛋白的表达水平、利用免疫沉淀法检测cyclophilin d乙酰化水平、利用流式细胞仪检测细胞凋亡。结果:1H2O2刺激使MSCs中Sirt3表达水平降低。2转染Sirt3可减少H2O2诱导的MSCs的凋亡,而转染Sirt3 si RNA可增加H2O2诱导的MSCs的凋亡。3Sirt3蛋白的含量并不影响cyclophilin d的表达,但影响cyclophilin d的乙酰化水平。结论:Sirt3可能通过减少线粒体通透性转换孔(mitochondrial permeablity transition pore,m PTP)中的关键蛋白cyclophilin d的乙酰化水平,进一步抑制m PTP的开放,从而减少H2O2诱导的MSCs的凋亡。     

过氧化氢对内皮祖细胞凋亡相关蛋白表达的影响

目的:比较不同浓度过氧化氢(hydrogen peroxide,H2O2)对人外周血来源的内皮祖细胞(endothelial progenitor cells,EPCs)生存能力的改变及其对凋亡相关蛋白表达的影响。方法:采用密度梯度离心法和差速贴壁法从人外周静脉血中分离培养内皮祖细胞。选取传代后第3代EPCs作为研究对象,以终浓度分别为50μmol/L、100μmol/L、150μmol/L、200μmol/L、300μmol/L和400μmol/L的过氧化氢处理内皮祖细胞12 h,同时设立正常处理对照组。CCK-8法检测各组内皮祖细胞生存能力的差异;Western blot分析各组内皮祖细胞中凋亡相关蛋白Bax、Bcl-2和p53的蛋白表达情况。结果:与对照组相比,在浓度为50μmol/L、100μmol/L和150μmol/L过氧化氢处理组中细胞存活能力逐渐增强,促凋亡蛋白Bax、p53随之下调,抗凋亡蛋白Bcl-2则显著上调;在浓度为200μmol/L、300μmol/L和400μmol/L过氧化氢处理组中细胞生存能力相对于正常对照组逐渐减弱,促凋亡蛋白Bax、p53表达水平逐渐增加,抗凋亡蛋白Bcl-2表达水平下降。结论:过氧化氢对内皮祖细胞存活能力和凋亡相关蛋白Bax、Bcl-2、p53表达的影响均呈双相性变化。     

Bifemelane Hydrochloride Protects Against Cytotoxicity of Hydrogen Peroxide on Cultured Rat Neuroblastoma Cell Line

Free radicals are involved in neuronal damage. Bifemelane hydrochloride has been reported to protect neural tissues against ischemic damage and age-related neurodegeneration. We examined the protective effects of bifemelane HCl and the relation between its effectiveness and free radical formation in hydrogen peroxide (H₂O₂)-induced cytotoxicity using cultured rat neuroblastoma cell line (B50). Cytotoxicity was examined by using the lactate dehydrogenase (LDH) assay and cell viability by the WST-1 assay. H₂O₂ reduced the survival of B50 cells in a dose-dependent manner, and treatment of these cells with 75 M or 100 M H₂O₂ reduced their viability by 50% relative to the control group. B50 cells were treated with 5 or 10 M bifemelane for 2 days followed by treatment with 75 M or 100 M H₂O₂. H₂O₂ cytotoxicity was reduced by pretreatment with bifemelane. We also examined the effect of bifemelane on lipid peroxide formation in B50 cells using thiobarbituric acid reactive substances assay. Pretreatment of B50 cells with 10 M bifemelane for 2 days reduced lipid peroxide formation to approximately 54% of the control group. Our results suggest that bifemelane hydrochloride provides a protective effect against H₂O₂ cytotoxicity partly due to its anti-oxidative properties.     

ROS与过氧化氢的研究现状及新进展

ROS作为动植物体内一系列生理生化反应的调控物质,长期备受关注。ROS中以过氧化氢为代表,是近年来研究的热点。近期研究表明,过氧化氢作为信号分子,在调控细胞的增殖、衰老、凋亡等方面起到不可替代的作用,成为当下研究热点。本综述就以过氧化氢为代表的ROS在机体内的产生、作用机理、信号通路及其与疾病治疗相关的前沿进展方面进行了讨论,旨在联系以过氧化氢为代表的ROS与机体相关的代谢途径与生理病理反应,为将来的研究及临床治疗等方面提供便利。     

An Improved Chemiluminescence Method for Hydrogen Peroxide Determination in Plant Tissues

As a consequence of the increasing importance of hydrogen peroxide in plant metabolism, more efficient methods are required for accurate determinations of its concentration in plant tissue and organs. Here we present a highly sensitive chemiluminescence (CL) method based on the Co (II) catalysed oxidation of luminol by H₂O₂. The replacement of ferricyanide, the traditional catalyst of luminol luminescence by Co (II), enhanced the sensitivity of the reaction towards H₂O₂ in three orders of magnitude. Thus, plant extracts can be diluted to such a level that quenching effects of phenols and ascorbic acid (ASA), which are normally present at high concentrations in plant tissues is avoided, and therefore, pre-treatments with PVP and ascorbate oxidase to remove these quenchers from plant-extracts become unnecessary. To exemplified the high performance of the method, measurements of H₂O₂ were carried out in PVP treated and non-treated extracts of grapevine leaf, a plant tissue that contain high levels of phenols and ASA. Moreover, increases in H₂O₂ levels were detected in disc-leaf treated with aminotriazole, a specific Cat inhibitor, showing the importance of Cat as a H₂O₂ scavenging enzyme in leaves of grapevine.     

Guattegaumerine Protects Primary Cultured Cortical Neurons Against Oxidative Stress Injury Induced by Hydrogen Peroxide Concomitant with Serum Deprivation

Guattegaumerine is a natural product with characteristics of being lipophilic and reaching high concentration in the brain, but its function in the central nervous system has not yet been observed. This study was designed to evaluate the neuroprotective effects of guattegaumerine on rat primary cultured cortical neurons. Following a 24-h exposure of the cells to combined serum-starvation and hydrogen peroxide, a significant augment in neuron damage as determined by 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT) assay and lactate dehydrogenase (LDH) release were observed. Preincubation of guattegaumerine dramatically improved the cell viability and inhibited LDH release. Preincubation of guattegaumerine also dramatically inhibited malondialhehyde (MDA) production and elevated the decreased total antioxidative capacity in cells caused by the combined injury. Results of flow cytometry and immunohistochemistry showed that pre-addition of guattegaumerine interrupted the apoptosis of the neurons, reversed the up regulation of the pro-apoptotic gene (Bax) and the down regulation of the anti-apoptotic gene (Bcl-2). Furthermore, guattegaumerine suppressed the increase of intracellular calcium ([Ca²⁺]_i) stimulated by either H₂O₂ or KCl in Ca²⁺-containing extracellular solutions, and high concentration of 2.5 μM guattegaumerine also suppressed the increase of [Ca²⁺]_i induced by H₂O₂ in Ca²⁺-free solution. These observations suggested that guattegaumerine may possess potential protection against oxidative stress injury, which might be beneficial for neurons.     

黄腐酸引发软骨细胞产生过氧化氢及硒的抑制作用

为探讨黄腐酸（FA）能否直接刺激软骨细胞产生活性氧以及硒能否抑制由此产生的活性氧,采用二氯荧光素双酯（DCFH－DA）作为软骨细胞产生过氧化氢的探针,用流式细胞技术定量地检测了在FA作用下软骨细胞产生的过氧化氢,并同时检测了硒存在时的过氧化氢含量．发现FA不但能够刺激软骨细胞产生过氧化氢（P＜0．05）,并与FA浓度相关,随FA浓度增大,产生过氧化氢增多,当FA浓度为100mg／L时软骨细胞产生过氧化氢达到最大,之后再增大FA浓度,过氧化氢的产生量减少;硒的存在对FA刺激软骨细胞产生过氧化氢有抑制作用．     

Release of Calcium from Mitochondrial and Nonmitochondrial Intracellular Stores in Mouse Pancreatic Acinar Cells by Hydrogen Peroxide

In the present study we have studied how [Ca²⁺] _i is influenced by H₂O₂ in collagenase-dispersed mouse pancreatic acinar cells and the mechanism underlying this effect by using a digital microspectrofluorimetric system. In the presence of normal extracellular calcium concentration, perfusion of pancreatic acinar cells with 1 mm H₂O₂ caused a slow sustained [Ca²⁺] _i increase, reaching a stable plateau after 10–15 min of perfusion. This increase induced by H₂O₂ was also observed in a nominally calcium-free medium, reflecting the release of calcium from intracellular store(s). Application of 1 mm H₂O₂ to acinar cells, in which nonmitochondrial agonist-releasable calcium pools had been previously depleted by a maximal concentration of CCK-8 (1 nm) or thapsigargin (0.5 μm) was still able to induce calcium release. Similar results were observed when thapsigargin was substituted for the mitochondrial uncoupler FCCP (0.5 μm). By contrast, simultaneous addition of thapsigargin and FCCP clearly abolished the H₂O₂-induced calcium increase. Interestingly, co-incubation of intact pancreatic acinar cells with CCK-8 plus thapsigargin and FCCP in the presence of H₂O₂ did not significantly affect the transient calcium spike induced by the depletion of nonmitochondrial and mitochondrial agonist-releasable calcium pools, but was followed by a sustained increase of [Ca²⁺] _i . In addition, H₂O₂ was able to block calcium efflux evoked by CCK and thapsigargin. Finally, the transient increase in [Ca²⁺] _i induced by H₂O₂ was abolished by an addition of 2 mm dithiothreitol (DTT), a sulfhydryl reducing agent. Our results show that H₂O₂ releases calcium from CCK-8- and thapsigargin-sensitive intracellular stores and from mitochondria. The action of H₂O₂ is likely mediated by oxidation of sulfhydryl groups of calcium-ATPases. Received: 15 May 2000/Revised: 4 October 2000     

The Effect of Hydrogen Peroxide on β-Adrenoceptor Function in the Heart

A membrane preparation of calf heart left ventricle has been used to study the effect of radical stress on the β-adrenoceptor complex. To this end the membranes were incubated for 30 minutes with several concentrations of hydrogen peroxide. This resulted in a dose dependent peroxidation of the membrane lipids. Preincubation with hydrogen peroxide in the concentration range 10^--⁷-^-10^--³M caused an increase in specific (—)-[¹²⁵I]-Iodocyanopindolol binding. possihly due to a decrease in membrane fluidity as a result of lipid peroxidation, thus making the receptor protein more accessible. Higher concentrations H₂O₂ reduced the specific (—)-[¹²⁵I]-lodocyanopindolol binding, which is most likely the effect of deterioration of the receptor protein by the more pronounced radical stress induced by these higher concentrations. Also adenylate cyclase activity was affected by radical stress. Basal cyclic-AMP production and cyclic-AMP production induced by NaF (10^--² M) or guanylylimidodiphosphate (10^--⁴ M), was suppressed after pretreatment with concentrations of H₂O₂ above 10^--⁴ M. This indicates a higher sensitivity of the adenylate cyclase toward radical stress when compared to the receptor protein. Our results show that radical stress can perturb β-adrenoceptor function considerably in the heart.