阿霉素预处理替代缺血预处理提供鼠肝缺血耐受力的实验研究

目的 探讨缺血预处理（IPC）延迟保护作用的发生机制以及应用阿霉素预处理（DPC）是否可以模拟IPC的延迟保护作用。方法 建立大鼠部分肝脏热缺血再灌注模型。IPC组采用肝脏缺血10min，再灌注10in，DPC组经静脉注射阿霉素（1mg/kg体重），对照组等量生理盐水注射。肝组织HSP70和HO－1蛋白和血清TNF－α、IL－10浓度分别采用Western blot法和ELISA法测定。结果 IPC后HO－1和HSP70含量分别于12h和24h达到高峰；IPC和DPC后24h诱导HSP70、HO－1的量无显著差异（P＞0.05）。对照组缺血再灌注后3h血清中TNF－α、AST、ALT、LDH及W／D（湿重／干重）的水平明显升高，而IL－10的含量降低，和假手术组相比差异显著（P＜0.01）；IPC或DPC后降低了TNF－α的释放和AST、ALT、LDH及W／D的水平，提高了IL－10的含量，和对照组相比差异显著（P＜0.01）。结论 IPC的延迟保护作用与HSP70和HO－1的诱导生成有关，DPC可以模拟IPC的延尺性保护作用，诱导HSP70和HO－1的产生。     

低氧预适应对大鼠肝癌肝切除术后残肝缺血再灌注中细胞凋亡的影响

目的 探讨低氧预适应诱导热休克蛋白70（HSP70）在大鼠肝癌肝切除术后对残肝细胞凋亡的影响及可能的作用机制.方法 采用SD大鼠移植性肝癌模型,根据随机表将60只模型鼠分为A组（假手术组）,B组（缺血状态下肝叶切除组）,C组（低氧预适应＋缺血状态下肝叶切除组）,每组20只.C组的处理方式：术前给予10％氮氧混合气体处理90 min,Pringle法完全阻断入肝血流15 min,同时切除肿瘤所在的肝左外叶.各组分别于术后1,8,12,24 h取残余肝脏标本,用Western blotting免疫印迹法检测HSP70、Bax蛋白的表达,应用流式细胞仪检测肝细胞凋亡率,下腔静脉取血检测ALT、AST,并在光镜下观察各组组织形态学改变,对相关数据进行统计学处理.结果 （1）与A、B组比较,C组检测的各同时相点HSP70的相对量表达明显增加,组间比较差异有统计学意义（均P＜0.05）,A、B组肝组织中仅有微量HSP70表达,两组比较差异无统计学意义（P＞0.05）;（2）与A组比较,B组各同时相点Bax蛋白表达水平明显升高,肝细胞凋亡率明显增加,两组比较差异有统计学意义（均P＜0.01或0.05）,而C组以上各项指标的变化均较B组明显减弱（均P ＜0.05）;（3）C组肝功能较B组改善明显,病理示A组肝组织形态基本正常,C组呈轻微病理学改变,而B组肝组织损伤明显加重.结论 低氧预适应对缺血条件下肝癌肝切除术产生的缺血再灌注损伤具有保护作用,其可能的机制之一是通过上调HSP70蛋白的表达,而HSP70通过降低Bax的表达,抑制细胞凋亡,从而发挥肝脏保护作用.     

丙泊酚对脑缺血-再灌注后海马组织热休克蛋白70和c-fos基因表达的影响

目的观察丙泊酚对脑缺血一再灌注后海马组织热休克蛋白70(HSP70)与c-fos基因表达的影响。方法雄性Wistar大鼠40只,随机分为假手术组、缺血一再灌注对照组和缺血一再灌注丙泊酚处理组,后者按丙泊酚用量又分为50、100和150mg／kg三个亚组。采用大鼠全脑缺血一再灌注损伤模型。全脑缺血10min再灌注60min时,断头取脑,采用免疫组织化学和半定量RT-PCR方法,对脑内HSP70与c-fos蛋白及其mRNA在海马组织的表达水平进行检测。结果缺血一再灌注后皮层、海马、纹状体及边缘区等脑区均有大量的HSP70和c-fos阳性蛋白表达,海马组织HSP70及c-fos基因mRNA的表达水平明显增高,其中以缺血一再灌注对照组表达最为显著;假手术组仅有少量阳性蛋白的表达,海马组织mRNA的表达水平极低;麻醉相关剂量的丙泊酚可显著抑制HSP70与c-fos蛋白在各脑区的表达,尤以海马CA1区最为显著,亦可明显下调HSP70和c-fos mRNA在海马组织的表达水平。结论缺血一再灌注损伤可明显诱导HSP70与c-fos基因的表达,丙泊酚的脑保护作用可能与其下调HSP70与c-fos基因的异常表达有关。     

抑肽酶对家兔全脑缺血-再灌注期白细胞介素-8基因的影响

目的 观察抑肽酶对家兔全脑缺血－再灌注期血清白细胞介素（IL）－8合成和释放的影响,并探讨其脑保护机制。方法 利用“六血管”阻断建立全脑缺血模型,24只家兔随机分为假手要组（A组）,缺血－再灌注组（B组）和抑肽酶组（C组）,每组8只兔。C组缺血30min再灌注4h,缺血前静注抑肽酶30000kIU/kg,随后每小时微量泵输注抑肽酶10000kIU/kg直至实验结束,B组为缺血－再灌注组,A组仅分离血管不阻断血流。分别在缺血前15min(10)及再灌注30min（R1）、2h（R2）和4h（R3）取颈内静脉血,测定血清IL－8浓度,实验结束取皮层苏木素－伊红染色,光镜观察白细胞浸润及神经元损伤程度。结果 C组IL－8随再灌注时间延长差异无显著性。B组由R1时的0.89ng/L迅速上升至R3时的1.46ng/L,分别增加2.28、2.97、3.74倍,同C组和A组相比差异有显著性;光镜下C组白细胞浸润及神经元损伤程度较B组明显减轻。结论 抑肽酶能有效抑制IL－8的合成和释放,这可能是抑肽酶减轻脑缺血－再 灌注损伤的重要机制。     

热休克蛋白73可保护鼠小肠热缺血-再灌注损害

在小肠移植中，防止缺血-再灌注（I／R）损害是一重要问题。由于对热休克蛋白73（HSP－73）保护I／R损害了解不多，作下列实验。取雄性Lewis鼠进行实验，麻醉下自颈总动脉插管，以便注药和采集血标本，分成3组：（1）第1组，注入亚砷酸钠（SA）以诱生HSP－73；第2组，注入磷酸盐缓冲盐水（PBS）作为对照；第3组，应用SA（6mg／kg）和槲皮素（5mg／kg）以阻断HSP－73的生成。24小时后剖腹，阻断肠系膜前动脉根部利。时，制成小肠缺血，去除血管夹后使小肠再灌注24小时。测血浆细胞因子和一氧化氮（NO）6次，即缺血前即刻及再灌注后…     

缺血预处理对大鼠肝脏缺血再灌注损伤的延迟性保护作用及其机制的初步探讨

目的探索减轻肝脏缺血再灌注损伤的有效措施及其机制.方法健康Wistar大鼠36只随机分为两组A组为缺血预处理组;B组为对照组.A组行缺血预处理,B组仅行开关腹.48 h后,再次开腹,先检测肝组织HSP70的表达,接着阻断肝左、中叶入肝血流45 min,再灌注90 min后检测肝组织TNF-α表达,分别于缺血前、缺血再灌注后检测血清ALT及镜下肝组织改变.结果 A组ALT水平明显低于B组.肝组织病变较B组轻.A组肝细胞HSP70表达明显,而B组HSP70表达不明显,A组肝脏TNF-α表达明显弱于B组.结论缺血预处理能减轻肝脏缺血再灌注损伤,这种保护作用是通过诱导肝细胞HSP70产生所致,HSP70能抑制肝组织TNF-α的产生.     

肝脏热休克蛋白表达的诱导方法与影响因素

热休克蛋白(heat shock protein,HSP)预表达可使机体避免或减轻由应激原引起的损害.肝部分切除术中常需阻断肝门以减少出血,但肝对热缺血耐受的安全时限仅为15～20min.肝移植时移植物须经受缺血、保存以及再灌注损伤,而有效地保存移植肝的活力,是减少和避免术后移植物原发性无功能(PNF)、保证移植成功的关键.因此,采取措施诱导肝脏预表达HSP以利用这一内源性保护物质,应是肝脏外科工作者关注的问题.     

丙泊酚对大鼠局灶性脑缺血-再灌注低氧诱导因子-1和热休克蛋白70的影响

目的 观察丙泊酚对大鼠局灶性脑缺血-再灌注后低氧诱导因子(HIF-1)和热休克蛋白70(HSP70)的影响,探讨丙泊酚脑保护作用机制.方法 32只雄性sD大鼠,随机均分为四组,采用可逆性大脑中动脉内线栓法建立局灶性脑缺血-再灌注模型,缺血2 h再灌注24 h后断头取脑,采用免疫组化法检测HIF-1和HSP70.HE染色,光镜观察细胞形态学改变.结果 大鼠局灶性脑缺血-再灌注后大脑皮质和海马区出现神经细胞的坏死和凋亡改变,HIF-1和HSP70的表达均增加,给丙泊酚后神经细胞的肿胀、坏死、凋亡明显减少,HIF-1和HSP70蛋白的表达受到明显抑制.结论 丙泊酚对大鼠局灶性脑缺血-再灌注损伤的保护机制与减少HIFll、HSP70的表达有关.     

丙泊酚对大鼠局灶性脑缺血-再灌注时脑组织热休克蛋白70基因和蛋白表达的影响

目的观察丙泊酚对大鼠局灶性脑缺血-再灌注时脑组织热休克蛋白(HSP)70 mRNA和HSP70蛋白表达的影响,以探讨其脑保护的机制。方法采用大脑中动脉线栓法建立大鼠局灶性脑缺血-再灌注模型。60只雄性Wistar大鼠,随机分为假手术组(Sham组)、缺血-再灌注组(I-R组)和丙泊酚组(P组),每组20只。大鼠脑缺血2 h,然后进行再灌注。在再灌注3、6、24、72 h断头取脑组织,采用原位杂交法和免疫组织化学染色检测大鼠脑组织HSP70 mRNA和HSP70蛋白的表达。结果局灶性脑缺血-再灌注后,HSP70 mRNA和HSP70蛋白的表达增加(P<0.01),但HSP70 mRNA表达较早,分布范围较广泛,而HSP70蛋白表达以半暗带区为主。应用丙泊酚能显著地促进脑缺血-再灌注后脑组织中HSP70 mRNA和HSP70蛋白的表达(P<0.01),与脑缺血-再灌注组相比较,HSP70 mRNA和HSP70蛋白不仅表达增多、范围增加,而且还能延缓下降(P<0.05)。结论丙泊酚能促进大鼠局灶性脑缺血-再灌注时HSP70的表达,这可能是其脑保护作用的部分机制。     

热休克蛋白70对肝硬化大鼠肝脏缺血再灌注损伤保护作用的研究

目的 探讨热休克蛋白70（HSP70）对肝硬化大鼠肝脏缺血再灌注损伤的保护作用。方法Wistar雄性大鼠用四氯化碳皮下注射制成肝硬化模型。分两组:IP组（缺血预处理组）,用 Pringle’s法阻断肝门15min后,恢复血供,关腹;C组（对照组）,只予以开、关腹。48h后,再次阻断肝门30min,恢复血供。用Western blotting法检测IP后6、24、48h肝组织中HSP70的表达水平;测再灌注1h血清生化酶（ALT、AST、LDH）水平;计算术后一周生存率,并行肝脏病理组织学检查。结果 IP组在缺血预处理后24-48hHSP70表达显著增强,呈高水平;而C组中在各时点HSP70均无表达增强。再灌注1h,IP组的ALT、AST、LDH水平显著低于C组（P<0.01或P<0.05,n=7）。术后一周生存率IP组（93.10％,n=29）明显高于C组（73.33％,n=30）（P<0.05）。缺血再灌注后1h,IP组的肝细胞损伤明显轻于C组。结论 HSP70能够减轻肝硬化大鼠肝脏缺血再灌注损伤,提高术后生存率。     

不同预处理对肝硬化兔缺血再灌注肝组织HSP70及ET-1表达的影响

目的:探讨两种预处理方式,即经典缺血预处理(IPC)与肢体缺血预处理(LIPC),对肝硬化兔肝缺血再灌注(I/R)损伤的保护作用及可能的作用机制。方法:皮下注射CCl4-橄榄油溶液制备兔肝硬化模型,随后将模型兔随机分为假手术组,肝I/R组(I/R组),IPC+肝I/R组(IPC组),LIPC+肝I/R组(LIPC组),每组7只。肝I/R模型制作方法:阻断入肝血流30 min,再灌注2 h;IPC诱导方法:在行肝I/R处理前阻断入肝血流10 min,开放10 min;LIPC诱导方法:在行肝I/R处理前24 h,采用止血带捆扎兔单侧后肢5 min,再开放5 min,重复3次。各组于再灌注2 h后切取肝组织,行组织形态学观察,用ELISA法测定内皮素1(ET-1)含量及Western blot法检测热休克蛋白(HSP70)的表达。结果:与假手术组比较,其余各组在肝硬化病变的基础上均出现不同程度的变性、水肿和炎性细胞浸润,但IPC组与LIPC组明显轻于I/R组,而LIPC组及IPC组间病变程度无明显差异;与假手术组比较,其余各组肝组织ET-1含量和HSP70的表达均明显增加(均P<0.05),但IPC组与LIPC组肝组织ET-1含量低于I/R组,HSP70的表达高于I/R组(均P<0.05),而上述2项指标在LIPC及IPC组间均无统计学差异(均P>0.05)。结论:LIPC和IPC均能对肝硬化肝I/R损伤有保护作用,且保护强度相似,其机制可能均与抑制ET-1的释放及增加HSP70的表达有关;LIPC具有无创性,可能具有更大的临床应用前景。     

Ozone oxidative preconditioning is mediated by A1 adenosine receptors in a rat model of liver ischemia/ reperfusion.

The liver is damaged by sustained ischemia in liver transplantation, and the reperfusion after ischemia results in further functional impairment. Ozone oxidative preconditioning (OzoneOP) protected the liver against ischemia/reperfusion (I/R) injury. The aim of this study was to investigate the role of A(1) adenosine receptor on the protective actions conferred by OzoneOP in hepatic I/R. By using a specific agonist and antagonist of the A(1) subtype receptor (2-chloro N6 cyclopentyladenosine, CCPA and 8-cyclopentyl-1,3-dipropylxanthine, DPCPX respectively), we studied the role of A(1) receptor in the protective effects of OzoneOP on the liver damage, nitiric oxide (NO) generation, adenosine deaminase activity and preservation of the cellular redox balance. Immunohistochemical analysis of nuclear factor-kappa B (NF-kappaB), tumor necrosis factor alpha (TNF-alpha) and heat shock protein-70 (HSP-70) was performed. OzoneOP prevented and/or ameliorated ischemic damage. CCPA showed a similar effect to OzoneOP + I/R group. A(1)AR antagonist DPCPX blocked the protective effect of OzoneOP. OzoneOP largely reduced the intensity of the p65 expression, diminished TNF-alpha production, and promoted a reduction in HSP-70 immunoreactivity. In summary, OzoneOP exerted protective effects against liver I/R injury through activation of A(1) adenosine receptors (A(1)AR). Adenosine and (.)NO produced by OzoneOP may play a role in the pathways of cellular signalling which promote preservation of the cellular redox balance, mitochondrial function, glutathione pools as well as the regulation of NF-kappaB and HSP-70.     

缺血或药物预处理对大鼠供肝缺血再灌注损伤的抑制作用

目的　探讨缺血预处理 (IPC)或阿霉素预处理 (DPC ,模拟IPC)对大鼠供肝延迟性保护作用的发生机制。方法　将供鼠分为 3组。IPC组 :供鼠采用肝脏预先缺血 10min后再开放 ;DPC组 :供鼠经静脉注射阿霉素 (1mg/kg体重 ) ;对照组 :供鼠用等量生理盐水注射。观察各组预处理后血红素氧化酶 1(HO 1)和热休克蛋白 70 (HSP70 )含量 ;建立上述各组大鼠原位肝移植模型 ,并设假手术对照组 ,观察肝移植后各组对供肝缺血再灌注损伤的影响。结果　IPC组HO 1、HSP70含量分别于预处理 12h和 2 4h达到高峰 ;IPC和DPC组预处理 2 4h ,诱导的HSP70、HO 1含量差异无显著性 (P >0 .0 5 )。对照组肝移植后 6h ,肝组织中ICAM 1mRNA表达和内皮细胞ICAM 1分子表达明显增强 ,髓过氧化物酶 (MPO)活性增高 ,血清中天冬氨酸转氨酶 (AST)、丙氨酸转氨酶 (ALT)、乳酸脱氢酶 (LDH)及肝组织湿重 /干重 (W/D)水平明显升高 ,和假手术组相比 ,差异有显著性 (P <0 .0 1)。IPC或DPC组肝移植后减弱了ICAM 1mRNA和蛋白表达及MPO活性 ,AST、ALT、LDH及W/D的水平亦明显降低 ,与对照组比较 ,差异有显著性 (P <0 .0 5 )。结论　IPC的延迟保护作用是通过降低中性粒细胞的粘附浸润来实现的 ,这与IPC诱导生成HSP70和HO 1有关。DPC可以模拟IPC的延迟性保护     

二氮嗪预处理抑制大鼠肝缺血再灌注所致细胞凋亡的延迟保护作用

目的：探讨二氮嗪(DE)预处理模拟缺血预处理(IP)抑制肝缺血再灌注(I/R)损伤所致细胞凋亡的延迟保护(DP)作用及其可能机制。方法：大鼠随机分为5组:IP组以肝缺血5min作I/R预处理;DE组静脉注射DE 作I/R预处理;DE+5-HD组在DE组基础上再予静脉注射5-HD作预处理;对照组(C组)仅以等量生理盐水作预处理;假手术组（S组）仅行2次开腹手术，不作其他处理。4个预处理组均在24h后行肝缺血1h再灌注3h。切取肝组织用免疫组化法检测Bcl-2蛋白表达及用TUNEL法检测肝细胞凋亡,并观察显微结构变化。结果： C组肝细胞凋亡指数(AI)明显高于S组(P<0.01),光镜与电镜下肝脏结构损伤明显;IP组与DE组Bcl-2蛋白表达指数(BI)高于C组(P<0.01),AI明显低于C组(P<0.05),组织损伤也轻于C组;而DE+5-HD组BI低于DE组(P<0.01),AI则高于DE组(P<0.05)。结论：使用DE预处理能模拟IP抗大鼠I/R损伤所致肝细胞凋亡的DP作用,可能系通过诱导肝细胞Bcl-2蛋白表达上调而发挥抗凋亡作用。     

Ozone oxidative preconditioning is mediated by A1 adenosine receptors in a rat model of liver ischemia/ reperfusion

The liver is damaged by sustained ischemia in liver transplantation, and the reperfusion after ischemia results in further functional impairment. Ozone oxidative preconditioning (OzoneOP) protected the liver against ischemia/reperfusion (I/R) injury. The aim of this study was to investigate the role of A₁ adenosine receptor on the protective actions conferred by OzoneOP in hepatic I/R. By using a specific agonist and antagonist of the A₁ subtype receptor (2-chloro N6 cyclopentyladenosine, CCPA and 8-cyclopentyl-1,3-dipropylxanthine, DPCPX respectively), we studied the role of A₁ receptor in the protective effects of OzoneOP on the liver damage, nitiric oxide (NO) generation, adenosine deaminase activity and preservation of the cellular redox balance. Immunohistochemical analysis of nuclear factor-kappa B (NF-κB), tumor necrosis factor alpha (TNF-α) and heat shock protein-70 (HSP-70) was performed. OzoneOP prevented and/or ameliorated ischemic damage. CCPA showed a similar effect to OzoneOP + I/R group. A₁AR antagonist DPCPX blocked the protective effect of OzoneOP. OzoneOP largely reduced the intensity of the p65 expression, diminished TNF-α production, and promoted a reduction in HSP-70 immunoreactivity. In summary, OzoneOP exerted protective effects against liver I/R injury through activation of A₁ adenosine receptors (A₁AR). Adenosine and ^.NO produced by OzoneOP may play a role in the pathways of cellular signalling which promote preservation of the cellular redox balance, mitochondrial function, glutathione pools as well as the regulation of NF-κB and HSP-70.     

缺血预处理对大鼠肝脏缺血再灌注损伤保护作用机制的研究

目的　探讨缺血预处理 (IPC)保护作用的发生机制。方法　建立大鼠部分肝脏热缺血再灌注模型。IPC采用肝脏缺血 10min ,再灌注 10min。结果　IPC后肝组织中腺苷和NO水平明显升高 ,与对照组相比差异显著 (P <0 0 1) ,但IPC前应用腺苷A2 受体拮抗剂后NO的升高被抑制 (P<0 0 1)。缺血再灌注 (I/R) 2h后血清中TNF α、AST、ALT、LDH及W/D水平和假手术组相比明显增加 ,而IL 10含量降低 (P <0 0 1) ;IPC、I/R前加入腺苷、IPC前应用腺苷A1受体拮抗剂显著地降低TNF α释放和AST、ALT、LDH及W /D水平 ,提高IL 10含量 ,与I/R组相比差异显著 (P <0 0 1) ;但IPC前应用腺苷A2 受体拮抗剂 (IPC +A2 antag)和NO合成酶抑制剂NAME并没有能像IPC组那样有效降低TNF α、AST、ALT、LDH及W /D的水平 ,提高IL 10的含量 (P <0 0 1) ;而IPC前给IPC+A2 antag组提供NO前体精氨酸又获得和IPC组同样的结果 (P >0 0 5 )。结论　IPC引起细胞外腺苷水平升高 ,腺苷A2 受体活化 ,介导了NO合成增加 ,最终通过抑制效应器TNF α的释放、增加IL 10的合成来实现对缺血组织的保护作用。     

缺血预处理对家兔脑缺血保护效应的实验研究

目的 探讨缺血预处理脑保护效应,以及神经细胞凋亡与缺血性脑损害的关系。方法 家兔１５只,随机分为３组,对照组,缺血组,缺血预处理组。Ａ组只做手术操作,Ｂ组采用二血管夹闭全脑缺血１０分钟,Ｃ组在缺血前增加缺血预处理２分钟再灌注３０分钟。对比观察缺血后３天海马ＣＡ１区神经元密度和缺血细胞数,同时使用ＴＵＮＥＬ原位标记法,检测缺血３天后海马区的凋亡细胞。     

Ischemic preconditioning provides both acute and delayed protection against renal ischemia and reperfusion injury in mice

Acute as well as delayed ischemic preconditioning (IPC) provides protection against cardiac and neuronal ischemia reperfusion (IR) injury. This study determined whether delayed preconditioning occurs in the kidney and further elucidated the mechanisms of renal IPC in mice. Mice were subjected to IPC (four cycles of 5 min of ischemia and reperfusion) and then to 30 min of renal ischemia either 15 min (acute IPC) or 24 h (delayed IPC) later. Both acute and delayed renal IPC provided powerful protection against renal IR injury. Inhibition of Akt but not extracellular signal-regulated kinase phosphorylation prevented the protection that was afforded by acute IPC. Neither extracellular signal-regulated kinase nor Akt inhibition prevented protection that was afforded by delayed renal IPC. Pretreatment with an antioxidant, N-(2-mercaptopropionyl)-glycine, to scavenge free radicals prevented the protection that was provided by acute but not delayed renal IPC. Inhibition of protein kinase C or pertussis toxin-sensitive G-proteins attenuated protection from both acute and delayed renal IPC. Delayed renal IPC increased inducible nitric oxide synthase (iNOS) as well as heat-shock protein 27 synthesis, and the renal protective effects of delayed preconditioning were attenuated by a selective inhibitor of iNOS (l-N(6)[1-iminoethyl]lysine). Moreover, delayed IPC was not observed in iNOS knockout mice. Both acute and delayed IPC were independent of A(1) adenosine receptors (AR) as a selective A(1)AR antagonist failed to block preconditioning and acute and delayed preconditioning occurred in mice that lacked A(1)AR. Therefore, this study demonstrated that acute or delayed IPC provides renal protection against IR injury in mice but involves distinct signaling pathways.     

Pharmacologic stimulation of adenosine A2 receptor supplants ischemic preconditioning in providing ischemic tolerance in rat livers

BACKGROUND: Ischemic preconditioning (IPC) is a promising strategy for conferring ischemic tolerance. We confirmed the acquisition of ischemic tolerance in the liver immediately after IPC and the role of adenosine kinetics in this process. METHODS: Male Lewis rats were used. IPC was administered with a 10-minute ischemia followed by a 10-minute reperfusion. Ischemic tolerance was tested with a 45-minute ischemia. Changes in the adenosine concentrations in liver tissue were evaluated, and the effects of adenosine A1 or A2 receptor agonists or antagonists were examined either in place of or against IPC. RESULTS: The 7-day animal survival was significantly better in the IPC group than in the control group (87% vs 53%; n = 15, P < .05). The release of liver-related enzymes during reperfusion was suppressed better in the IPC group (P < .01). Recovery of adenosine triphosphate levels was faster in the IPC group (P < .01). After IPC, adenosine concentrations in liver tissue immediately increased to 1555 +/- 299 pmol/g wet tissue and were maintained at that level during a subsequent 45-minute ischemia. The ischemic tolerance generated by IPC was mimicked by the administration of adenosine A2 receptor agonist and opposed by adenosine A2 receptor antagonist. CONCLUSIONS: The ischemic tolerance of the liver immediately after IPC can be supplanted by selective pharmacologic stimulation of adenosine A2 receptors.