PD 81,723, an allosteric enhancer of the A1 adenosine receptor, lowers the threshold for ischemic preconditioning in dogs.
PD 81,723, an allosteric enhancer of the A1 adenosine receptor, lowers the threshold for ischemic preconditioning in dogs.
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DOI：
10.1161/01.res.79.3.415
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发表时间：
1996-09
影响因子：
20.1
通讯作者：
T. Mizumura;J. Auchampach;J. Linden;R. F. Bruns;G. Gross
中科院分区：
文献类型：
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作者：
T. Mizumura;J. Auchampach;J. Linden;R. F. Bruns;G. Gross
PD 81723 （PD）的变构作用是增加激动剂与A1腺苷受体的结合，并增强心脏和其他组织中A1受体介导的功能性反应。为了确定PD是否降低了缺血预处理（PC）的阈值，我们对麻醉的狗进行了60分钟的左冠状动脉前降支（LAD）闭塞和3小时的再灌注。闭塞60分钟前10分钟，LAD闭塞2.5分钟或5分钟产生缺血性PC。PD（总剂量100微克/千克，冠状动脉血液中5 ~ 50 μ mol/L）或载药在非pc犬或缺血2.5分钟预处理犬的60分钟闭塞期前17.5分钟注入冠状动脉内。心肌梗死面积由三苯基四唑染色确定，并以危险面积的百分比表示。与对照组（26.3 +/- 3.6%，平均+/- SEM）相比，单独使用PC 2.5分钟（23.4 +/- 4.2%）或单独使用PD（26.5 +/- 1.7%）对梗死面积没有显著影响，但PD + PC （14.6 +/- 1.7%, P < 0.05）或更长时间（5分钟）单独使用PC（12.5 +/- 3.3%）可使梗死面积减小。静脉注射A1腺苷受体选择性拮抗剂8-环戊基-1,3-二丙基黄嘌呤（1mg /kg）或atp敏感的K+通道阻滞剂格列本脲（0.3 mg/kg） 15分钟后，PD + PC阻断了保护作用（分别为23.6 +/- 2.3%或25.9 +/- 3.3%）。所研究的化合物均未影响全身血流动力学、侧支血流或AAR。为了确定哪种犬腺苷受体亚型受到10 μ mol/L PD的影响，我们使用表达重组犬受体和激动剂放射配体的COS-7细胞的膜进行了放射配体结合研究。PD可使[125I] n6 -4-氨基-3-碘苄基腺苷（125I- aba）与A1受体的解离速率提高2.18倍，但对[125I]-[2-（4-氨基-3-碘苯基）乙胺]腺苷与A3受体的解离动力学无影响。格列本脲浓度高达10 μ mol/L时，对放射性配体与重组犬A1、A2A或A3受体的结合没有影响。这些数据表明，PD通过增强腺苷与其A1受体的结合，减少了缺血产生预适应所需的时间。格列本脲通过不涉及腺苷受体阻断的机制阻止A1受体激活所提供的保护。
PD 81,723 (PD) acts allosterically to increase agonist binding to A1 adenosine receptors and to enhance functional A1 receptor-mediated responses in the heart and other tissues. To determine if PD lowers the threshold for ischemic preconditioning (PC), pentobarbital-anesthetized dogs were subjected to 60 minutes of left anterior descending coronary artery (LAD) occlusion and 3 hours of reperfusion. Ischemic PC was produced by either 2.5 or 5 minutes of LAD occlusion 10 minutes before the 60-minute occlusion. PD (100 micrograms/kg total dose, 5 to 50 mumol/L in coronary arterial blood) or vehicle was infused intracoronarily for 17.5 minutes before the 60-minute occlusion period in non-PC dogs or in dogs preconditioned with 2.5 minutes of ischemia. Myocardial infarct size was determined by triphenyltetrazolium staining and expressed as a percentage of the area at risk. Compared with the control group (26.3 +/- 3.6%, mean +/- SEM), infarct size was not significantly affected by 2.5 minutes of PC alone (23.4 +/- 4.2%) or by PD alone (26.5 +/- 1.7%) but was decreased by PD + PC (14.6 +/- 1.7%, P < .05) or by a longer period (5 minutes) of PC alone (12.5 +/- 3.3%). The intravenous administration of the selective antagonist of A1 adenosine receptors, 8-cyclopentyl-1,3-dipropylxanthine (1 mg/kg), or the ATP-sensitive K+ channel blocker, glibenclamide (0.3 mg/kg), for 15 minutes before PD + PC blocked the protection (23.6 +/- 2.3% or 25.9 +/- 3.3%, respectively). None of the compounds studied affected systemic hemodynamics, collateral blood flow, or AAR. To determine which subtypes of canine adenosine receptors were affected by 10 mumol/L PD, radioligand binding studies were conducted using membranes derived from COS-7 cells expressing recombinant canine receptors and agonist radioligands. PD enhanced the binding of [125I]N6-4-amino-3-iodobenzyladenosine (125I-ABA) to A1 receptors by increasing the t1/2 for dissociation by 2.18-fold, but PD had no effect on the dissociation kinetics of 125I-ABA from A3 receptors or [125I]-[2-(4-amino-3-iodo-phenyl)ethylamino] adenosine from A2A receptors. Glibenclamide at concentrations up to 10 mumol/L had no effect on the binding of radioligands to recombinant canine A1, A2A, or A3 receptors. These data suggest that PD reduces the amount of time required for ischemia to produce preconditioning by enhancing adenosine binding to its A1 receptor. Glibenclamide prevents the protection afforded by A1 receptor activation by a mechanism not involving adenosine receptor blockade.