ALPHA-1 ADRENERGIC RESPONSES IN SMOOTH MUSCLE

该提案的目标涉及α 1肾上腺素能受体的作用， 平滑肌中的受体，特别强调通过 所述儿茶酚胺诱导α 1受体介导的 应答 脱敏是指组织反应性的丧失 在长时间暴露于激动剂药物或激素后。 我们有 证明了血管中的几种适应性变化有助于 α 1受体介导的平滑肌收缩脱敏 是因为长时间暴露在儿茶酚胺中 本申请提出 为了进一步研究这些变化的分子基础， 功能 我们已经发现阿尔法受体的长期激活 诱导血管平滑肌内皮释放增强的 大量的内皮衍生舒张因子（EDRF）; α受体 内皮细胞上的亚型（α 1A vs α 1B;或α 2）， 将确定这种效应。 的解释 将通过以下方法寻求由儿茶酚胺诱导的EDRF的增强释放： 测定一氧化氮合酶基因在 内皮细胞对儿茶酚胺的反应，以确定是否 如已经发现的那样，儿茶酚胺诱导一氧化氮合酶 for various各种cytokines细胞因子. 增强的病理生理学意义 将在两只大鼠中测定由儿茶酚胺诱导EDRF释放 模型，嗜铬细胞瘤（一种分泌去甲肾上腺素的肿瘤）和 在长时间输注治疗中常用的血管加压剂后 心血管休克 我们发现， 受体刺激导致蛋白激酶C下调 血管平滑肌;表达变化的机制 平滑肌中发现的各种蛋白激酶C亚型将被 测定 蛋白激酶C转换的潜在改变 脱敏平滑肌的同工酶及其基因表达 将寻找细胞。 我们将调查长期使用的影响 α 1受体对α 1B受体表达的激活 培养的大鼠主动脉平滑肌细胞。 根据我们的初步数据， 关于α 1受体作用的其它研究是 提出了 平滑肌细胞中蛋白激酶C的激活导致 增强α 1受体的表达;我们建议确定 这一重要的监管变化的基础，通过调查 α 1B肾上腺素能受体5'调控区的结构 基因 刺激α 1受体导致表达激活 c-fos基因在大鼠主动脉中的表达 我们建议调查的作用 平滑肌收缩对肾上腺素能受体的脱敏作用 诱导c-fos表达及EDRF对其的影响 反应 后一项研究暗示了 α 1激动剂和血管紧张素II对平滑肌细胞生长的影响。

The goals of this proposal relate to the action of alpha1 adrenergic receptors in smooth muscle with particular emphasis on mechanisms by which catecholamines induce desensitization of alpha1 receptor-mediated responses. Desensitization refers to loss in responsiveness of a tissue after prolonged exposure to an agonist drug or hormone. We have demonstrated that several adaptations in blood vessels contribute to desensitization of alpha1 receptor-mediated smooth muscle contraction after prolonged exposure to catecholamines. this application proposes to investigate further the molecular basis underlying these changes in function. We have found that prolonged activation of alpha receptors induces the endothelium of vascular smooth muscle to release enhanced amounts of endothelial derived relaxing factor (EDRF); the alpha receptor subtype on endothelial cells (alpha1A vs alpha1B; or alpha2) which transduces this effect will be determined. The explanation for the enhanced release of EDRF induced by catecholamines will be sought by determining the expression of the nitric oxide synthase gene in endothelial cells in response to catecholamines to determine if catecholamines induce nitric oxide synthase as has been found to occur for various cytokines. The pathophysiological significance of enhanced release of EDRF induced by catecholamines will be determined in two rat models, one of pheochromocytoma (a norepinephrine-secreting tumor) and after prolonged infusions of vasopressors commonly used in the treatment of cardiovascular shock. We have found that prolonged alpha1 adrenergic receptor stimulation leads to down-regulation of protein kinase C in vascular smooth muscle; the mechanism for changes in expression of various protein kinase C isoforms found in smooth muscle will be determined. Potential alterations in the turnover of protein kinase C isozymes and the expression of their genes in desensitized smooth muscle cells will be sought. We will investigate the effects of prolonged activation of alpha1 receptors on expression of alpha1B receptors in cultured rat aorta smooth muscle cells. Based on our preliminary data, additional studies relating to the action of alpha1 receptors are proposed. Activation of protein kinase C in smooth muscle cells leads to enhanced expression of alpha1 receptors; we propose to determine the basis for this important regulatory change by investigation of the structure of the 5' regulatory region of the alpha1B adrenergic receptor gene. Stimulation of alpha1 receptors leads to activation of expression of the c-fos gene in rat aorta. We propose to investigate the role of desensitization of smooth muscle contraction on adrenergic receptor- mediated induction of expression of c-fos and the effects of EDRF on this response. These latter studies have implications for the effects of alpha1 agonists and angiotensin II on smooth muscle cell growth.