ACUTE PULMONARY ARTERIAL RESPONSES TO HYPOXIA

缺氧的急性肺动脉反应

• 批准号: 2228932
• 负责人: J T SYLVESTER
• 金额: $ 28.58万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-12-01 至 1999-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2228932
• 关键词: acidity /alkalinity; acidosis; biological signal transduction; calcium; diacylglycerols; electrical property; glycolysis; hypoxia; inositol phosphates; intracellular; membrane potentials; muscle cells; muscle tension; nuclear magnetic resonance spectroscopy; oxidative phosphorylation; potassium channel; pulmonary artery; swine; vascular endothelium; vascular smooth muscle; vasomotion

In precontracted proximal intrapulmonary arteries, severe hypoxia caused a triphasic response: (1) early transient contraction, which was endothelium-dependent and reduced by L-NAME; (2) relaxation, which was endothelium-independent, reduced by glibenclamide, and associated with decreased smooth muscle energy state and intracellular pH; and (3) late sustained contraction, which was endothelium-dependent, unaffected by L- NAME or indomethacin, and associated with recovery of smooth muscle energy state and intracellular pH. In pulmonary arterial myocytes, severe hypoxia caused depolarization and decreased outward potassium currents, which were inhibited by 4-aminopyridine, but not TEA or charybdotoxin. Based on these results, we propose that the direct effect of hypoxia on pulmonary arterial smooth muscle is depolarization, which occurs because delayed rectifier potassium (Kdr) channels are inhibited, perhaps secondary to desaturation of a sarcolemmal heme protein. If and when this direct effect is expressed as increased vasomotor tone, however, depends on many factors, including baseline membrane potential, intracellullar calcium concentration ({ca2+}i), energy state, and intracellular pH in smooth muscle, as well as the presence or absence of endothelial influences. With respect to proximal intrapulmonary arteries, we hypothesize, first, that early hypoxic contraction is caused by inhibition of basal endothelium-derived NO activity. Although hypoxia inhibits Kdr channels in smooth muscle, leading to depolarization, activation of voltage-dependent calcium channels, and calcium influx, these events do not contribute to early hypoxic contraction because the depolarization is too small and the rise in {Ca2+}i too slow to trigger contraction before the onset of hypoxic relaxation. Second, hypoxic relaxation is caused by inhibition of receptor-linked vasoconstrictor transduction pathways and activation of ATP-dependent potassium (KATP) channels in smooth muscle, both of which result from energy state deterioration and intracellular acidosis secondary to decreased oxidative phosphorylation. Third, late hypoxic contraction is caused by endothelial factors which upregulate glycolysis and improve energy state in smooth muscle, leading to normalization of intracellular pH via enhanced Na-H exchange; improved transduction of receptor-linked vasoconstrictor stimuli, including an endothelium-derived contractile factor; and depolarization secondary to inactivation of KATP channels and direct hypoxic inhibition of Kdr channels. To test these hypotheses, we will perform experiments in proximal intrapulmonary and systemic arteries of the pig, measuring membrane potential, ion currents, {Ca2+}i, and intracellular pH in arterial myocytes; isometric tension, 31P nuclear magnetic resonance spectroscopy, glucose utilization, lactate production, and concentrations of inositol phosphates and diacylglycerol in arterial rings; and transmural pressure-diameter relations and bioassays of endothelial factors in perfused arteries. By elucidating the direct effects of hypoxia on pulmonary arterial smooth muscle, and how these effects are altered by endothelium, we hope to improve understanding of in vivo pulmonary vasomotor responses to hypoxia, which have been difficult to study mechanistically in intact animals or isolated lungs. Understanding these responses is important, because they optimize oxygen exchange in normal lungs and cause pulmonary hypertension, cor pulmonale, and increased mortality in patients with chronic lung disease.

在预收缩的近端肺内动脉中，严重的低氧导致 三相反应：(1)早期短暂性收缩， 血管内皮细胞依赖，并被L的名字减少；(2)松弛，这是 非内皮依赖性，可被格列本脲降低，并与 平滑肌能量状态和细胞内pH降低；以及(3)迟发 持续收缩，这是内皮依赖的，不受L的影响- 名称或吲哚美辛，与恢复平滑肌能量有关 状态和细胞内pH。在肺动脉肌细胞中，严重缺氧 引起去极化并减少外向钾电流，这是 可被4-氨基吡啶抑制，但不能被茶叶或轮虫毒素抑制。基于这些 结果提示，低氧对肺动脉的直接作用 平滑肌是去极化的，这是因为延迟整流 钾(KDR)通道被抑制，可能继发于去饱和 一种肌膜血红素蛋白。如果以及当这种直接影响被表达时 然而，由于血管舒缩张力的增加取决于许多因素，包括 基线膜电位、细胞内钙离子浓度 ([Ca~(2+)]i)、能量状态、细胞内pH以及 内皮细胞影响的存在或不存在。关于…… 近端肺内动脉，我们假设，首先，早期缺氧 收缩是由抑制基础内皮源性NO引起的 活动。尽管缺氧抑制了平滑肌上的KDR通道，但导致 去极化，激活电压依赖性钙通道，以及 钙内流，这些事件不会导致早期缺氧性收缩 因为去极化太小，而钙离子的上升太慢， 在低氧松弛开始之前触发收缩。第二, 低氧松弛是由受体连接的抑制引起的 血管紧张剂转导通路与ATP依赖的激活 平滑肌中的钾(KATP)通道，这两者都是由 继发性能量状态恶化和细胞内酸中毒 氧化磷酸化程度降低。第三，晚期缺氧性收缩是 由促进糖酵解和改善的内皮因子引起的 平滑肌中的能量状态，导致细胞内pH正常化 通过增强Na-H交换；改善受体连接的转导 血管收缩刺激，包括内皮来源的收缩 以及KATP通道失活和继发的去极化。 直接缺氧性抑制KDR通道。为了检验这些假设，我们 将在近端肺内动脉和全身动脉进行实验 测量膜电位、离子电流、[Ca~(2+)]i和 动脉肌细胞内pH；等长张力，31P核 磁共振波谱，葡萄糖利用，乳酸产生， 动脉中肌醇磷酸盐和二酰甘油的浓度 环；跨壁压力-直径关系和生物测定 血管内皮细胞因子在动脉中的作用。通过阐明直接的 低氧对肺动脉平滑肌的影响及其机制 血管内皮细胞的作用是改变的，我们希望提高对In的认识 活体肺血管对低氧的反应，这已经很难 在完整的动物或分离的肺中进行机械研究。理解 这些反应很重要，因为它们优化了体内的氧交换 肺功能正常，可引起肺动脉高压、肺源性心脏病，并增加 慢性肺病患者的死亡率。