AI ADENOSINE RECEPTOR IN CULTURED HEART CELLS

本研究的主要目的是研究这一进程和 心脏A1腺苷的脱敏和增敏机制 受体(A1AR)介导的生理反应，以确定是否改变 在A1AR水平和/或高亲和力形式的A1AR调节 心脏对A1AR激动剂刺激的生理反应性 确定A1AR激活导致高血压的分子机制(S) A1AR介导的收缩反应。体外培养的单层心房细胞 以14日龄雏鸡胚胎为模型系统。具体来说，我们会： A)描述A1AR激动剂引起的功能反应 刺激；b)开展放射性配基结合的生物化学研究 这些培养细胞膜上A1AR的拮抗剂和激动剂。 我们将进一步确定1)A1AR是否与各种 潜在的效应物，如腺苷环化酶、磷酸二酯酶、 鸟苷环化酶或钾通道，我们将研究其作用 这些潜在效应器在调节A1AR收缩效应中的作用 2)百日咳毒素敏感的GTP结合蛋白(S)参与 A1AR与各种效应器之间的偶联；3)慢性暴露 培养的心房细胞对A1AR激动剂的作用减弱 介导性功能反应以及这种降低的反应性是否 与高亲和力A1AR向低亲和力A1AR的转换相关联 形式，下调A1AR，或两者兼而有之；4)慢性治疗 用腺苷受体拮抗剂或腺苷脱氨酶培养 通过引起A1AR介导的功能反应的敏化 将低亲和力的A1AR转换为高亲和力的形式 受体上调或通过这两种机制；5)脱敏 A1AR伴随着刺激性激素水平的补偿性增加 G蛋白(Gs)或β-肾上腺素能受体(βAR)及其伴随 对β-肾上腺素能刺激的反应性增强；6)另一方面 另一方面，这些抑制性受体的敏化与 代偿性降低的Gs或βAR水平伴随而来 β-肾上腺素能反应性下降。这些研究应该会有所帮助 阐明A1AR的增敏和减敏机制 系统以及A1AR及其高亲和力的调节作用 心房肌细胞对A1AR激动剂敏感性的调节机制 刺激。他们还应该提供对这些机制的见解 负责腺苷的细胞活动。

The main objectives of the present study are to study the process and mechanism of desensitization and sensitization of the cardiac A1 adenosine receptor (A1AR)-mediated physiologic response, to determine whether changes in the levels of A1AR and/or the high-affinity form of the A1AR regulate physiologic responsiveness of the heart to A1AR agonist stimulation, and to determine the molecular mechanism(s) by which activation of A1AR causes the A1AR-mediated contractile response. Monolayer atrial cells cultured from 14 day chick embryo will be used as a model system. Specifically, we will: a) characterize the functional responses elicited by A1AR agonist stimulation; b) carry out biochemical studies of the binding of radioligand antagonist and agonist to the A1AR in membranes of these cultures cells. We will further determine whether 1) A1AR are coupled to the various potential effectors such as the adenylate cyclase, phosphodiesterase, guanylate cyclase or the potassium channel, and we will study the role of these potential effectors in mediating the contractile effects of A1AR agonist; 2) pertussis toxin-sensitive GTP-binding protein(s) is involved in the coupling between A1AR and the various effectors; 3) chronic exposure of cultured atrial cells to A1AR agonist causes attenuation of the A1AR- mediated functional responses and whether such decreased responsiveness is associated with a conversion of the high-affinity A1AR to a low-affinity form, a downregulation of the A1AR, or both; 4) chronic treatment of the culture with an adenosine receptor antagonist or adenosine deaminase induces sensitization of the A1AR-mediated functional response by causing the conversion of low-affinity A1AR to a high-affinity form, an upregulation of the receptor or by both mechanisms; 5) desensitization of A1AR is accompanied by a compensatory increase in the level of stimulatory G protein (Gs) or beta-adrenergic receptors (beta AR) with a concomitant increase in responsiveness to beta-adrenergic stimulation; 6) on the other hand, sensitization of these inhibitory receptors is associated with a compensatory decrease in the level of Gs or beta AR with concomitant decrease in beta-adrenergic responsiveness. These studies should help elucidate the mechanism of sensitization and desensitization of the A1AR system as well as the role of the regulation of A1AR and its high-affinity form in modulating the sensitivity of atrial myocytes to A1AR agonist stimulation. They should also provide insights into the mechanisms responsible for the cellular action of adenosine.