CARDIAC A1-ADENOSINE RECEPTOR RESERVE

心脏 A1-腺苷受体储备

• 批准号: 2735335
• 负责人: LUIZ BELARDINELLI
• 金额: $ 28.38万
• 依托单位: UNIVERSITY OF FLORIDA
• 依托单位国家: 美国
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-07-01 至 2001-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2735335
• 关键词: adenosine; beta adrenergic receptor; cardiovascular agents; electrophysiology; guinea pigs; heart cell; heart function; heart rhythm; inhibitor /antagonist; muscle cells; purinergic receptor; receptor expression; receptor sensitivity; stimulant /agonist; tissue /cell culture; voltage /patch clamp

DESCRIPTION: (Adapted from the Applicant's Abstract) Recent studies in the applicants' laboratory revealed that the potency of adenosine to inhibit isoproterenol-stimulated L-type calcium inward current (beta-ICa,L) of atrial myocytes is 12-fold higher than to activate the inwardly rectifying K+ current (IKAdo). The studies proposed in this application are designed to test the following hypotheses related to the differential potency of adenosine to inhibit beta-ICa,L and to activate IKAdo in atrial myocytes: Aim #1 - distinct A1 receptor subtypes (A1a and A1b) subserve inhibition of beta-ICa,L and activation of IKAdo; Aim #2 - a single receptor is coupled to both responses, but there is a greater receptor reserve for inhibition of beta-ICa,L than for activation of IKAdo; Aim #3 - different A1AdoR agonists will have different magnitudes of receptor reserve. The importance of receptor reserve as a determinant of cardiomyocyte responsiveness to A1AdoR agonists will be resolved. A newly synthesized irreversible A1AdoR antagonist will be used to inactivate A1AdoRs for the analysis of receptor reserve. Pharmacological methods will be used to define A1AdoR subtypes and to determine the receptor occupancy-response relationships for both A1AdoR-mediated responses (activation of IKAdo/inhibition of beta-Ica,L) in atrial myocytes and for the direct shortening of the atrial monophasic action potential (MAP) caused by various A1AdoR agonists. Studies will be carried out with guinea pig freshly isolated atrial myocytes and isolated perfused hearts. Activation of IKAdo and inhibition of beta-ICa,L by adenosine and A1AdoR agonists will be recorded by use of the whole cell patch-clamp technique. Shortening of the atrial MAP caused by adenosine and by A1AdoR agonists will be quantitated by standard electrophysiological methods. Although the main focus of this project is on receptor reserve, they will also investigate (Aim #4) whether the higher potency and potentially greater reserve for the anti beta-adrenergic action may confer tonic inhibition by endogenous adenosine of sympathetic activation of the heart in the anesthetized guinea pig. The hypothesis that endogenous adenosine exerts tonic inhibition of the cardiostimulatory effects of increased sympathetic neural activity will be tested by measuring the magnitude of reflex tachycardia caused by nitroprusside-induced hypotension, in the absence and presence of A1AdoR antagonists and of an allosteric enhancer of agonist binding to the A1AdoR. The studies will have important clinical implications for the design and use of A1AdoR agonists in the treatment of cardiac disease, and for the role for adenosine in regulation of cardiac function. The long-term goal of the studies is to understand mechanisms by which organ and/or response selectivity to A1AdoR agonists is achievable.

描述：（改编自申请人的摘要）最近的研究 申请人的实验室揭示了腺苷抑制的效力 异丙肾上腺素刺激的 L 型钙内向电流 (β-ICa,L) 心房肌细胞比激活内调高12倍 K+ 电流 (IKAdo)。 本申请中提出的研究旨在 检验以下与差异效力相关的假设 腺苷抑制心房肌细胞中的 β-ICa,L 并激活 IKAdo： 目标 #1 - 不同的 A1 受体亚型（A1a 和 A1b）有助于抑制 beta-ICa,L 和 IKAdo 的激活；目标#2——单个受体偶联 两种反应，但有更大的受体储备来抑制 beta-ICa,L 比 IKAdo 的激活；目标 #3 - 不同的 A1AdoR 激动剂 将具有不同程度的受体储备。 的重要性 受体储备作为心肌细胞对 A1AdoR 反应性的决定因素 激动剂将得到解决。 新合成的不可逆A1AdoR 拮抗剂将用于灭活 A1AdoRs 以进行受体分析 预订。 药理学方法将用于定义 A1AdoR 亚型和 确定两者的受体占据-反应关系 A1AdoR 介导的反应（激活 IKAdo/抑制 β-Ica,L） 心房肌细胞和心房单相的直接缩短 由各种 A1AdoR 激动剂引起的动作电位 (MAP)。 研究将是 用豚鼠新鲜分离的心房肌细胞进行并分离 灌注的心。 激活 IKAdo 并抑制 β-ICa,L 腺苷和 A1AdoR 激动剂将通过使用全细胞进行记录 膜片钳技术。 腺苷引起的心房 MAP 缩短 A1AdoR 激动剂将通过标准电生理学进行定量 方法。 虽然这个项目的主要重点是受体储备， 他们还将调查（目标#4）是否具有更高的效力和 抗β-肾上腺素能作用的潜在更大储备可能会赋予 内源性腺苷对交感神经激活的强直性抑制 麻醉豚鼠的心脏。 内生假设 腺苷对心脏刺激作用具有强直抑制作用 交感神经活动的增加将通过测量 由硝普钠引起的低血压引起的反射性心动过速的程度， 在 A1AdoR 拮抗剂和变构剂不存在和存在的情况下 激动剂与 A1AdoR 结合的增强子。 这些研究将具有重要意义 A1AdoR 激动剂的设计和使用的临床意义 心脏病的治疗以及腺苷在调节中的作用 心脏功能。 研究的长期目标是了解 器官和/或对 A1AdoR 激动剂的选择性反应的机制 可以实现的。