STIMULUS SECRETION COUPLING IN CAROTID BODY GLOMUS CELLS

颈动脉体球细胞的刺激分泌耦合

• 批准号: 2029294
• 负责人: DAVID F. DONNELLY
• 金额: $ 16万
• 依托单位: YALE 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 1998-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2029294
• 关键词: acidosis; afferent nerve; calcium channel; calcium flux; carotid body; catecholamines; chemoreceptors; enzyme activity; hypoxia; laboratory rat; microelectrodes; nucleotides; phosphorylases; potassium channel; secretion; sodium channel; synaptic vesicles; voltage /patch clamp

The primary sensor of the respiratory and cardiovascular systems for hypoxia are the carotid body chemoreceptors which increase their activity in response to a decrease in PaO2 or PHa. Sensitivity to these stimuli are weak at birth and increase over the first week or two of life. Hypoxia and acidity are likely transduced by glomus cells, secretory cells in apposition to the afferent nerve endings. Their role is essential to chemotransduction because chemosensitivity is lost following separation of the glomus cell from the nerve endings. Recent patch clamp recordings of isolated glomus cells revealed a K+ current which is inhibited by hypoxia. This inhibition is hypothesized to play an essential role in the transduction cascade of hypoxia, leading to depolarization, calcium influx and enhanced transmitter release. However, our preliminary question the validity of this mechanism because hypoxia often fails to alter membrane currents of glomus cells, in situ, and K+ blocking agents, although greatly effecting the cellular currents, may not block the nerve or secretory response of the organ. The proposed experiments address two basic questions regarding the transduction process. Firstly, what is the identity of glomus cell secretogues and which are liberated during hypoxia? This is addressed by examining: i) the importance of Na+, K+ and Ca+2 channels in initiating glomus cells secretion, ii) the relationship between Ca+2i and cell secretion and iii) the modulatory role of nucleotides and phosphorylases on secretory activity. Secondly, what change occurs in the level of or sensitivity to secretogues to account for the developmental increase in glomus cell stimulus/secretion coupling? The proposed experiments will employ a new and unique chemoreceptor model which allows for simultaneous single-fiber nerve recordings and either measurement of catecholamine release or patch-clamp recording of glomus cell. Patch-clamp data is used for assessment of vesicular fusion events by high-resolution monitoring of membrane capacitance. Catecholamine secretion is measured using carbon-fiber, Nafion coated microelectrodes combined with scanning or amperometric voltammetry. The anticipated results from this work will allow us to better understand the mechanisms of glomus cell hypoxia and acidity transduction and the basis for the maturational increase in sensitivity to these physiologic stimuli. This may lead to therapeutic strategies that can alter chemosensitivity and thereby improve treatment of apnea and hypoventilation in the neonate and older subject.

呼吸和心血管系统的主要传感器 缺氧是颈动脉体化学感受器的活性增加 响应 PaO2 或 PHa 的降低。对这些刺激的敏感性是 出生时较弱，并在出生后一两周内增加。缺氧和 酸度可能是由血管球细胞、分泌细胞转导的 与传入神经末梢并置。他们的作用至关重要 化学转导，因为化学敏感性在分离后丧失 来自神经末梢的血管球细胞。最近的膜片钳记录 分离的血管球细胞显示出受缺氧抑制的 K+ 电流。 假设这种抑制作用在 缺氧转导级联，导致去极化、钙内流 和增强的发射器释放。然而，我们初步质疑 这种机制的有效性，因为缺氧通常无法改变膜 血管球细胞的电流，原位和 K+ 阻断剂，尽管 极大地影响细胞电流，可能不会阻塞神经或 器官的分泌反应。 所提出的实验解决了两个基本问题 转导过程。一、肾小球细胞的身份是什么 缺氧时会释放哪些促分泌剂？这是通过解决 检查：i) Na+、K+ 和 Ca+2 通道在启动中的重要性 血管球细胞分泌，ii) Ca+2i 与细胞的关系 分泌以及 iii) 核苷酸和磷酸化酶的调节作用 关于分泌活动。其次，水平或水平发生什么变化？ 对分泌物的敏感性，以解释发育增加 血管球细胞刺激/分泌耦合？ 拟议的实验将采用一种新的、独特的化学感受器模型 允许同时进行单纤维神经记录，并且 儿茶酚胺释放测量或血管球膜片钳记录 细胞。膜片钳数据用于评估囊泡融合事件 通过膜电容的高分辨率监测。儿茶酚胺 使用碳纤维、Nafion 涂层微电极测量分泌物 与扫描或电流伏安法相结合。 这项工作的预期结果将使我们更好地了解 血管球细胞缺氧和酸度转导的机制及其 对这些生理学敏感性的成熟增加的基础 刺激。这可能会导致治疗策略改变 化学敏感性，从而改善呼吸暂停的治疗 新生儿和老年受试者通气不足。