维生素E在大鼠肝脏缺血再灌注损伤中的作用

目的探讨维生素E在肝组织缺血再灌注(I/R)损伤的保护机制及对缺血预处理(IP)的影响。方法采用大鼠原位半肝缺血再灌注和缺血预处理模型,缺血前通过灌胃给予维生素E(250mg/kg),分析血清丙氨酸转氨酶(ALT)、天冬氨酸转氨酶(AST)、乳酸脱氢酶(LDH)、全血还原型谷胱甘肽(GSH)、肝组织脂质过氧化物(LPO)、超氧化物歧化酶(SOD)含量及肝组织病理改变等各项指标。结果I/R导致明显的肝损伤,IP减轻肝I/R损伤,维生素E能减轻肝组织缺血再灌注损伤,但可以部分抵消IP的保护作用。结论维生素E能减轻肝组织缺血再灌注损伤,其作用是通过减少氧自由基产生而实现的。IP对鼠肝I/R有明显的保护作用,IP期间产生的一定量的自由基,对随后的I/R的保护作用具有重要意义。维生素E导致氧自由基减少是肝IP保护作用的不利因素。     

血小板激活因子及其拮抗剂银杏内酯B对大鼠心肌缺血再灌注损伤的影响(英文)

目的　探讨外源性血小板激活因子 (PAF)激活的多核形中性粒细胞 (PMN)是否具有低浓度氧自由基模拟缺血预适应 (IP)对缺血再灌注 (IR)所致心肌损伤的保护作用。方法　结扎冠脉左前降支 30min ,再灌注 3h制备大鼠心脏IR模型。以缺血前给予 2次 5min缺血 ,10min再灌注作为IP。实验分为6组 ,IR组、IR +PAF组和IR +银杏内酯B(GB、PAF拮抗剂 )组 ,分别于缺血前 2 5和 10miniv生理盐水、PAF(3μg·kg- 1)和GB (5mg·kg- 1) ;IP +IR组、IP +IR +PAF组和IP +IR +GB组分别于IP 2次 10min再灌注开始时iv相应药物。观察分析心功能、梗死面积、PMN计数、心肌髓过氧化物酶活性、TUNEL阳性细胞计数等指标。结果　给予PAF明显加重IR引起的心脏损伤、PMN浸润及凋亡的程度 ;GB对IR引起的心功能下降没有明显影响 ,但明显减少梗死面积、PMN浸润及凋亡细胞 ;PAF明显削弱IP的保护作用 ;GB对IP作用未见明显影响。结论　IR后PMN浸润可能是引起心肌细胞凋亡的一个重要原因 ;PAF激活PMN可能不具有模拟IP对IR所致心肌损伤的保护作用 ,反而取消IP的保护作用。     

卡巴胆碱减轻肠缺血/再灌注大鼠中性粒细胞活化和多器官损伤

目的探讨胆碱能激动剂——卡巴胆碱对肠缺血/再灌注大鼠中性粒细胞活化的影响及其对脏器功能的保护作用。方法雄性Wistar大鼠随机分为假手术组(N)、肠缺血/再灌注组(I/R)及卡巴胆碱组(Car)。夹闭肠系膜上动脉45min后恢复灌流制成肠I/R模型;卡巴胆碱组在肠缺血15min后经幽门注射卡巴胆碱(100μg/kg体质量)。于缺血45min(I45)、再灌注1h(R1)、2h(R2)、6h(R6)取肠系膜上静脉血进行中性粒细胞(PMN)计数、测定PMN呼吸爆发强度、检测反映脏器功能的血浆酶学指标以及肠和肺组织髓过氧化物酶(MPO)活性。结果肠缺血45min,PMN计数下降,再灌注后逐渐回升,至R6时达高峰。Car组PMN计数在R2和R6时显著低于I/R组大鼠;PMN呼吸爆发强度的变化规律与PMN计数一致。相关分析表明,PMN化学发光峰值变化和血PMN计数的变化呈正相关(r=0.748,P<0.05)。大鼠小肠组织MPO活性在肠缺血和再灌注均升高(P<0.05),R6达最高;Car组小肠MPO活性在肠I/R各时间点均显著低于I/R组(P<0.05～P<0.01)。肺组织MPO活性在肠缺血期降低,再灌注后逐渐升高,在R6时MPO活性达高峰(P<0.01),而此时Car组大鼠肺组织MPO活性仅为I/R组的31%(P<0.01),接近N组。GI/R组大鼠血浆天冬氨酸转氨酶(AST)、丙氨酸转氨酶(ALT)、肌酐(Cr)、肌酸激酶-同工酶(CK-MB)在肠缺血后均升高,R2时达峰值(P<0.01),R6时仍高于N组(P<0.05)。Car组大鼠各指标在再灌注后均较I/R组同时相点低,以R2组效果最明显(P<0.01)。结论卡巴胆碱能显著抑制PMN活化,减轻GI/R引起的多脏器功能损伤。     

姜黄素预处理对大鼠肢体缺血再灌注肺损伤时血红素加氧酶-1的影响

目的:探讨姜黄素预处理对大鼠肢体缺血再灌注肺损伤时血红素加氧酶-1(HO-1)的影响。方法:建立大鼠肢体缺血2h再灌注3h肺损伤模型。60只大鼠随机等分为5组:假手术组(Sham)、姜黄素组(Cur)、缺血再灌注组(I/R)、姜黄素+缺血再灌注组(Cur-I/R)和锌原卟啉IX(ZnPP)+姜黄素+缺血再灌注组(ZnPP-Cur-I/R)。ZnPP-Cur-I/R组于缺血前24h经腹腔注射ZnPP 20mg/kg,Cur组、Cur-I/R组和ZnPP-Cur-I/R组分别于缺血前2h经腹腔注射姜黄素200mg/kg,其余各组给予等容量生理盐水。除Sham组和Cur组外,其余各组行肢体缺血再灌注。观察肺组织病理学变化,测定肺组织损伤评分、湿/干重比(W/D)、中性粒细胞(PMN)数目和HO-1mRNA及其蛋白表达的情况。结果:与Sham组比较,I/R组肺组织损伤较重,肺损伤评分、W/D及PMN计数升高,HO-1mRNA及其蛋白表达上调(P<0.01);与I/R组比较,Cur-I/R组肺组织损伤减轻,肺损伤评分、W/D及PMN计数降低,HO-1mRNA及其蛋白表达上调(P<0.01);与Cur-I/R组比较,ZnPP-Cur-I/R组肺组织损伤加重,肺损伤评分、W/D及PMN计数升高,HO-1mRNA及其蛋白表达下调(P<0.01)。结论:姜黄素预处理可通过上调肺组织HO-1的表达减轻大鼠肢体缺血再灌注肺损伤。     

己酮可可碱对肠缺血-再灌注损伤的影响

目的 观察多形核中性粒细胞(PMN)在多器官损伤中的作用,PMN活化抑制药己酮可可碱对肠缺血-再灌注损伤的保护作用. 方法 采用大鼠肠缺血-再灌注损伤的模型,将大鼠随机分为PTX组(n＝15)、缺血-再灌注组(I/R,n＝15),假手术组(n＝15)和对照组(n＝15). 用戊巴比妥钠(40 mg.kg^-1)腹腔注射麻醉后,消毒腹部皮肤,铺无菌巾. PTX组和I/R组动物行剖腹术,分离并夹闭肠系膜上动脉,1 h后松夹,PTX组立即给予己酮可可碱(50 mg.kg^-1,腹腔注射),I/R组给予等量0.9%氯化钠溶液,关闭腹腔. 再灌注5 h后采集门、体静脉血,取小肠、肝及左肺组织,行右肺灌洗并收集支气管肺泡灌洗液(BALF). 假手术组仅行剖腹术和肠系膜上动脉分离术,不夹闭肠系膜上动脉,关闭腹腔6 h后取标本. 对照组麻醉后立即取标本. 观察指标：肠组织病理分级; 门、体静脉血内毒素测定; BALF中蛋白含量测定; 肠、肺组织中髓过氧化酶(MPO)含量测定及肝组织中PMN浸润程度. 结果 肠缺血-再灌注可导致肠及远端器官肝、肺中PMN聚集明显增加,并伴有这些器官的损伤; 己酮可可碱可明显抑制肠缺血-再灌注引起的PMN聚集,同时肠、肝、肺组织损伤的指标明显改善. 结论 肠缺血-再灌注造成PMN在肠及远端器官中的聚集增多,是导致多器官损伤的重要原因; 己酮可可碱可减轻肠缺血 再灌注引起的多器官损伤,这一作用至少部分是通过抑制PMN的活化和聚集而实现.     

三七总皂甙对大鼠移植肝ICAM-1表达的影响

目的 探讨三七总皂甙(PNS)预处理在大鼠肝移植缺血/再灌注损伤(I/R)中的保护作用及其对细胞间粘附分子-1(ICAM-1)表达的影响.方法 雄性SD大鼠分别用作供、受体,采用Kamada's袖套改良法建立原位肝移植模型,根据供肝切取前1 h是否静脉注射PNS(50 mg/kg)将大鼠随机分为PNS预处理组(PNS组)和NS对照组(NS组);另设假手术作对照组(SO组).分别于供肝再灌注后2h、6h及24h处死各组动物,检测血清ALT及AST,HE切片作病理组织学检查,比色法测定髓过氧化物酶(MPO)的含量,RT-PCR法检测ICAM-1 mRNA的表达.结果 供肝再灌注后2h、6h及24h各时点,PNS组大鼠血清ALT及AST水平均明显低于NS组(P＜0.05);再灌注后6h,NS组大鼠肝组织的MPO含量明显高于PNS组(P＜0.05);供肝再灌注后2h、6h,PNS组大鼠肝组织ICAM-1 mRNA的相对表达水平明显低于NS组(P＜0.05).结论 PNS预处理大鼠供肝,可以有效地减轻大鼠肝移植I/R损伤;PNS对肝移植I/R损伤的保护作用可能与抑制ICAM-1的表达及中性粒细胞(PMN)的浸润有关.     

甲磺酸加贝酯在小肠缺血-再灌注损伤中的预防作用

目的 观察多形核中性粒细胞(PMN)在小肠缺血-再灌注(I/R)损伤中的作用.方法 采用新西兰白兔I/R损伤模型,将健康新西兰白兔随机分为I/R损伤组、药物治疗组、对照组和假手术组,各15只.阻断肠系膜上动脉(SMA)1 h后,药物治疗组立即给予颈外脉注射甲磺酸加贝酯30 mg/kg,I/R组立即给予等量0.9％氯化钠注射液.再灌注6h后采集体静脉及门静脉血,收集支气管-肺泡灌洗液(BALF),并取肝、肺及小肠组织;假手术组仅行SMA分离术,术后6h取标本;对照组麻醉后立即取标本.测定门、体静脉血内毒素及肺、肠组织中髓过氧化酶(MPO)舍量,观察肝组织中PMN浸润程度;肠组织病理分级,测定BALF中蛋白含量.结果 肠I/R损伤可导致肝、肺、肠等远端器官中PMN聚集明显增加(P＜0.05);甲磺酸加贝酯可以抑制肠I/R损伤引起的PMN聚集,减轻组织器官损伤.结论 PMN在肠I/R损伤中活化聚集是导致全身炎性反应及多器官功能损伤的重要原因之一,甲磺酸加贝酯通过抑制PMN的活性及炎性介质的释放而减轻组织器官的损伤.     

缺血预处理对肝脏抗氧化能力的影响及机制

目的 在大鼠肝脏原位缺血再灌注(I/R)模型上观察缺血预处理(IP)对肝脏抗氧化能力的影响及其机制。方法 在大鼠肝脏原位缺血再灌注模型上,心包穿刺抽血,切取肝组织,分别进行血清ALT、AST检测,肝组织MDA、SOD、Cat、GSH-PX测定。结果 发现预处理组与缺血再灌注组相比血清中ALT、AST水平及肝组织匀浆中MDA的含量降低,而肝组织中SOD、Cat及GSH-PX的活性均不同程度增高,多数检测指标各预处理组之间均无明显差异。结论 实验表明缺血预处理能增强缺血再灌注肝脏的抗氧化能力,增加预处理的次数并不能增加预处理的效果。腺苷在缺血预处理过程中起着重要作用。     

大鼠双后肢缺血预处理对肝脏缺血再灌注后能量代谢和脂质代谢的影响

为了观察动物双后肢缺血预处理 ( IPC)对肝脏缺血再灌注 ( I/ R)损伤的保护作用 ,探讨 IPC器官保护作用的普遍性及其机制 ,将实验动物分为正常对照 ( S)组、肝脏 I/ R组、肝脏 IPC组及双后肢 IPC组 ,比较各组动物肝组织中能量物质 ATP、ADP、AMP、腺苷 ( ADO)及脂质过氧化物丙二醛 ( MDA)含量的变化。结果显示 ,双后肢 IPC组及肝脏 IPC组肝组织中 ATP、ADP、AMP、ADO含量明显高于 I/ R组 ,P<0 .0 1;而 MDA含量则明显低于 I/ R组 ,P<0 .0 1     

腺苷对肺再灌注损伤时中性粒细胞CD11b/CD18的影响

目的:探讨腺苷预处理对肺缺血再灌注(I/R)全身炎性反应损伤的抑制作用。方法:60只大耳白兔无特定病原体动物(SPF)随机分为3组,每组20只。I组未行缺血再灌注处理;II组行左肺缺血再灌注处理;III组行左肺缺血再灌注处理,并于术前10min经颈静脉给予腺苷(adenosine)。采用在体肺缺血再灌注损伤模型,分别于缺血45min,再灌注1,2,4h流式细胞仪测定CD11b/CD18-FITC标记的中性粒细胞(PMN)阳性细胞百分率及左肺组织湿干质量比的变化。结果:Ⅱ组再灌注后各时点CD11b/CD18表达及左肺组织湿干质量比显著高于I组和III组(P<0.01或P<0.05),结论:腺苷预处理可抑制PMN表面CD11b/CD18表达的上调,减轻肺血管内皮细胞的损伤。     

Protective effect of a specific platelet-activating factor antagonist, BN 52021, on bupivacaine-induced cardiovascular impairments in rats

Administration of the local anaesthetic bupivacaine (1.5 or 2 mg/kg, i.v.) to rats elicited a marked decrease of mean arterial blood pressure (MBP) and heart rate (HR) leading to death (in 67% or 90% of animals respectively). Intravenous injection of the specific platelet-activating factor (PAF) antagonist BN 52021 (10 mg/kg), 30 min before bupivacaine administration (2 mg/kg i.v.) suppressed both the decrease of MBP and HR. In contrast, doses of 1 mg/kg BN 52021 given 30 min before or 10 mg/kg administered 5 min before i.v. injection of bupivacaine were ineffective. When BN 52021 (20 mg/kg i.v.) was injected immediately after bupivacaine (2 mg/kg), a partial reversion of the decrease of MBP and HR was observed, whereas the dose of 10 mg/kg was ineffective. A partial recovery of bupivacaine-induced ECG alterations was observed after pretreatment of the rats with BN 52021. Since the administration of BN 52021, at all doses studied, did not alter MBP and HR at the doses used, the bulk of these results clearly demonstrate a protective action of BN 52021, a specific antagonist of PAF, against bupivacaine-induced cardiovascular toxicity. Thus, consistent with its direct effect on heart, PAF appears to be implicated in bupivacaine-induced cardiovascular alterations.     

预处理对肝脏的保护作用

目的　评价缺血预处理 (IPC)对大鼠肝脏的保护作用。方法　在原位灌注的大鼠肝脏缺血再灌注模型上观察 IPC的保护作用。结果　预处理可阻止血清丙氨酸转氨酶 (AL T)、天冬氨酸转氨酶 (AST)、乳酸脱氢酶 (L DH)及脂质过氧化物 (L PO)水平增高 ,而使组织超氧化歧化酶 (SOD)保持在较高水平。结论　缺血预处理对大鼠肝脏有保护作用     

Endothelium-dependent vasodilation in the isolated rabbit kidney following in vivo and in vitro ischaemia and reperfusion: effects of antagonizing platelet activating factor (PAF)

Renal ischaemia-reperfusion (I/R) is a pathological condition occurring frequently after transplantation and acute renal failure. A mediator thought to play a role in the disturbed haemodynamics of I/R is platelet activating factor (PAF). We studied endothelium-dependent (acetylcholine, ACh) and -independent (sodium nitroprusside, SNP) vasorelaxant responses and the effect of BN 52021, a PAF antagonist, in the isolated perfused rabbit kidney after in vivo and in vitro I/R. Anaesthetized rabbits underwent right nephrectomy and 1 h left renal artery clamping followed by 30min reperfusion with blood. In another group, kidneys were isolated and, after transferral to the perfusion system, the perfusion pump was turned off for 1 h, followed by 30min reperfusion with Krebs' solution. BN 52021 or its vehicle dimethylsulphoxide (DMSO) was administered 20min before left renal artery occlusion or turning off the pump. Although in vitro I/R did not influence ACh-induced responses, in vivo I/R caused a decrease which was prevented by BN 52021. SNP-induced responses did not change in in vitro I/R and decreased only at lower concentrations in in vivo I/R, whereby pretreatment with BN 52021 did not offer any protection. It is concluded that in vivo I/R diminishes ACh-induced endothelium-dependent vasodilation, possibly via PAF and blood components, whereas SNP-induced endothelium-independent vasodilation was not altered by in vivo and in vitro ischaemia in the isolated rabbit kidney.     

Alpha-lipoic acid protects against hepatic ischemia-reperfusion injury in rats

BACKGROUND AND AIM: To evaluate the protective effect of alpha-lipoic acid in reducing oxidative damage after severe hepatic ischemia/reperfusion (IR) injury. METHODS: Wistar albino rats were subjected to 45 min of hepatic ischemia, followed by 60 min reperfusion period. Lipoic acid (100 mg/kg i.p.) was administered 15 min prior to ischemia and immediately before reperfusion period. At the end of the reperfusion period aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH) activity, and cytokine, TNF-alpha and IL-1beta levels were determined in serum samples. Malondialdehyde (MDA), and glutathione (GSH) levels and myeloperoxidase (MPO) activity were determined in the liver tissue samples while formation of reactive oxygen species was monitored by using chemiluminescence (CL) technique with luminol and lucigenin probes. Tissues were also analyzed histologically. Results: Serum ALT, AST, and LDH activities and TNF-alpha and IL-1beta levels were elevated in the I/R group, while this increase was significantly lower in the group of animals treated concomitantly with lipoic acid. Hepatic GSH levels, significantly depressed by I/R, were elevated back to control levels in lipoic acid-treated I/R group. Furthermore, increases in tissue luminol and lucigenin CL, MDA levels and MPO activity due to I/R injury were reduced back to control levels with lipoic acid treatment. CONCLUSION: Since lipoic acid administration alleviated the I/R-induced liver injury and improved the hepatic structure and function, it seems likely that lipoic acid with its antioxidant and oxidant-scavenging properties may be of potential therapeutic value in protecting the liver against oxidative injury due to ischemia-reperfusion.     

银杏苦内酯对急性胰腺炎大鼠的治疗作用及机制

观察血小板活化因子受体特异性拮抗刘银杏苦内酯（ＢＮ５２０２１）对牛磺胆酸钠诱导的急性胰腺炎（ＡＰ）大鼠的治疗作用及其对胰腺组织丙二醛（ＭＤＡ）．ＳＯＤ和Ｃａ２＋的影响。结果表明：ＢＮ５２０２１显著降低ＡＰ大鼠死亡率，延长平均存活时间、降低血清淀粉酶活性、减轻胰组织病理损伤；显著降低胰组织Ｃａ２＋含量和ＭＤＡ含量、提高ＳＯＤ活性。提示ＢＮ５２０２１对ＡＰ大鼠有一定治疗作用，此与其抑制钙超载、清除自由基有关。     

The effect of the specific PAF antagonist BN 52021 and the calcium blocker diltiazem on PAF induced arrhythmogenicity

Platelet-activating factor (PAF) in a concentration of 10(-11) mole per animal decreased the threshold doses for onsets of arrhythmia, ventricular flutters and fibrillation in ouabain induced arrhythmia in guinea-pigs in a statistically significant manner. The specific PAF antagonist BN 52021 (20 mg/kg, orally) completely inhibited the PAF effect for all types of arrhythmia, while the Ca2+ antagonistic drug diltiazem (0.1 mg/kg, i.v.) failed to counteract the PAF action. BN 52021 (20 mg/kg, per os) alone did not exert any effect on ouabain induced arrhythmia, but as expected, diltiazem (0.1 mg/kg, i.v.) showed antiarrhythmic effects. These results confirm the specific PAF antagonistic activity of BN 52021, its usefulness for PAF related cardiac rhythm disturbances and indicate that the method used could be a further useful tool to screen PAF antagonistic substances.     

Effect of intraportal verapamil infusion on hepatic ischemia-reperfusion injury.

Removal of free oxygen radicals, generated during reperfusion of an ischemic organ by scavengers protects the tissue from reperfusion injury. The calcium channel blocker verapamil is an effective cytoprotective agent, preventing against reperfusion injury. The effects of verapamil were investigated previously using hepatic, renal or cardiac ischemia-reperfusion injury models. We investigated the effects of intravenous and intraportal administration of verapamil in prevention from the injury caused by free oxygen radicals generated during hepatic ischemia-reperfusion in rats. Thirty six male Sprague-Dawley rats after laparotomy were subjected to hepatic ischemia for 30 and 45 min followed by 60 min of reperfusion. Two minutes before ischemia the rats were pretreated by intravenous or intraportal administration of verapamil. The levels of glutathione and thiobarbituric acid reacting substances (TBARs) referred to as malonyldialdehyde (MDA) and the serum levels of transaminases were measured in liver tissue 1 and 24 h after the onset of reperfusion. Statistical analysis of the data by Student's t-test showed statistically significant differences between the group pretreated intraportally with verapamil and the other groups. Verapamil given intraportally exerted more beneficial effect. Therefore, we conclude that intraportal verapamil administration reduces the ischemia-reperfusion injury caused by free oxygen radicals.     

Ginkgolide B protects isolated hearts against arrhythmias induced by ischemia but not reperfusion

The effect of ginkgolide B (BN 52021), a specific platelet-activating factor (PAF) antagonist, applied in doses of 1.5, 3.0, 6.0 X 10(-5) and 1.2 X 10(-4) mol/l, in comparison to that of metoprolol (10(-5) mol/l) and diltiazem (10(-7) mol/l), two widely used antiarrhythmic agents, on ischemia- and reperfusion-induced arrhythmias and heart functions, such as heart rate (HR), coronary flow (CF), aortic flow (AF), left ventricular developed pressure (LVDP), its first derivative (LVdp/dtmax), and left ventricular end-diastolic pressure (LVEDP) in isolated working rat hearts was examined. BN 52021 caused a dose-related protection against dysrhythmias, such as ventricular fibrillation, ventricular tachycardia, and premature ventricular beats induced by ischemia (30 min ligation of the left anterior descending coronary artery). The antiarrhythmic effect of BN 52021 given in a dose of 6.0 X 10(-5) mol/l was comparable to that of diltiazem and superior to the activity of metoprolol. None of the drugs influenced reperfusion-induced rhythm disturbances. BN 52021 did not alter heart functions, while metoprolol reduced (LVEDP only, and diltiazem increased CF, decreased AF, LVDP, and LVdp/dtmax during regional ischemia, indicating a negative inotropic effect. The antiarrhythmic effect of BN 52021 appears to be related to an antagonism of an increase in slow calcium influx induced by PAF in myocardial cells. Similarly to the mechanism of action of established antiarrhythmic drugs, BN 52021 can presumably prevent the re-entry mechanism involved in the development of ischemia-induced rhythm disturbances.     

Comparison of the actions of some platelet-activating factor antagonists on platelets and aortic smooth muscles.

The pharmacological actions of five platelet-activating factor (PAF) antagonists were compared in rabbit platelets and rat thoracic aorta. In PAF (2 ng/ml)-induced aggregation of washed rabbit platelets, WEB 2086 and WEB 2170 much were more potent inhibitors than BN 52021, kadsurenone and denudatin B, and the IC50 values were calculated to be 0.1, 0.3, 5, 8 and 10 micrograms/ml, respectively. WEB 2086, WEB 2170 and BN 52021 did not affect the platelet aggregation caused by collagen (10 micrograms/ml), ADP (20 microM), arachidonic acid (100 microM) or thrombin (0.1 U/ml). Kadsurenone and denudatin B suppressed ATP release, thromboxane B2 formation and the rise in intracellular calcium of washed rabbit platelets caused by collagen and thrombin, while WEB 2086, WEB 2170 and BN 52021 did not have an effect. Norepinephrine (3 microM) induced a sustained contraction in rat thoracic aorta. Pretreatment with these PAF antagonists (20-100 micrograms/ml) caused inhibition of the aortic contraction in the following order: kadsurenone greater than denudatin B greater than WEB 2086 greater than BN 52021 greater than WEB 2170. In high potassium (60 mM)-induced contraction of rat aorta, kadsurenone and denudatin B caused marked relaxation, while WEB 2086, WEB 2170 and BN 52021 had only a slight effect. It is concluded that WEB 2086, WEB 2170 and BN 52021 are specific PAF antagonists in rabbit platelets, and weak relaxants in rat aorta. Two other PAF antagonists, kadsurenone and denudatin B, may inhibit some aspects of signal transduction, e.g., thromboxane formation or intracellular Ca2+ mobilization in rabbit platelets, and cause vasorelaxation in rat aorta by inhibiting calcium influx.