CELLULAR ACIDIFICATION MECHANISMS: RESPIRATORY DISORDERS

细胞酸化机制：呼吸系统疾病

基本信息

批准号：
3237399
负责人：
NICOLAOS E MADIAS
金额：
$ 16.44万
依托单位：
TUFTS MEDICAL CENTER
依托单位国家：
美国
项目类别：
财政年份：
1988
资助国家：
美国
起止时间：
1988-03-15 至 1991-02-28
项目状态：
已结题

项目摘要

It is the overall objective of the present proposal to investigate the cellular representation of the proximal-tubule acidification response to changes in PaCO2 in the rabbit and the dog utilizing membrane-vesicle methodologies. Our understanding of the cellular mechanisms of basal proximal acidification remains incomplete. Moreover, the mechanisms that mediate the adaptation of proximal acidification to respiratory disorders are largely unknown. Therefore, the specific aims of the present proposal are: 1) To further our knowledge on the multitude of the cellular systems of proximal acidification and to characterize their functional expression under normal acid-base conditions. 2) To explore the cellular mechanisms and the time-course of the adaptation of proximal acidification to acute and chronic changes in PaCO2. Changes in PaCO2 induce prompt, directional changes in proximal-tubule acidification. When the alterations in PaCO2 are sustained, additional, much larger, and slowly-evolving changes in the rate of bicarbonate reabsorption ensue that require several days for completion. Given the slowly-evolving nature of the changes in acidification, it is hypothesized that the renal response reflects graded adaptation and/or sequential recruitment of several cellular systems of acidification. It is further hypothesized that these adaptations occur in a coordinated fashion aiming at the maintenance of the intracellular milieu despite brisk changes in transcellular ionic fluxes. Cellular systems to be investigated include Na+-H+ and pH-dependent C1- transporters in brush-border vesicles (BBMV), H+ ATPase in cortical endosomes and BBMV, Na+-HCO3- cotransport in basolateral vesicles (BLMV), and Na+-dependent glutamine and phosphate uptake in BBMV and BLMV. Characterization of these systems in the basal state will be followed by studies during respiratory disorders. Hypercapnia and hypocapnia will be induced in unanesthetized animals within a large environment chamber. The adaptation of the above systems of proximal acidification will be examined at intervals of 1 hour, 1 day, and 5 days from induction of the respiratory disturbance. Preliminary results in support of widespread adaptive changes in the activity of the cellular systems of proximal acidification following 4 days of hypercapnia or 5 days of hypocapnia have been obtained; notably, BLMV Na+-HCO3- cotransport was not altered after only 1 hour of hypercapnia, nor had adaptation occurred in the BBMV Na+-H+ exchanger after 1 day of hypercapnia. These studies may provide important new insights into the mechanism and regulation of proximal acidification under basal conditions as well as during acute and chronic changes in PaCO2.

本提案的总体目标是调查近端小管酸化的细胞表征兔子和狗对 PaCO2 变化的反应膜囊泡方法。我们的理解基础近端酸化的细胞机制仍然存在不完整。此外，调解机制近端酸化对呼吸系统疾病的适应是很大程度上不为人知。因此，当前的具体目标建议是： 1）加深我们对众多近端酸化的细胞系统并表征它们在正常酸碱条件下的功能表达。 2）探索细胞机制和时间过程近端酸化对急性和慢性变化的适应在 PaCO2 中。 PaCO2 的变化会引起迅速、方向性的变化近端小管酸化。当 PaCO2 发生变化时是持续的、额外的、更大的、并且缓慢发展的碳酸氢盐重吸收率发生变化，需要几天才能完成。鉴于缓慢发展的性质酸化的变化，推测肾反应反映了分级适应和/或顺序招募几种细胞酸化系统的研究。更是进一步假设这些适应以协调的方式发生旨在维持细胞内环境的时尚尽管跨细胞离子通量发生了快速变化。蜂窝网络要研究的系统包括 Na+-H+ 和 pH 依赖性 C1- 刷状缘囊泡 (BBMV) 中的转运蛋白、H+ ATP 酶皮质内体和 BBMV、Na+-HCO3- 共转运基底外侧囊泡 (BLMV) 和 Na+ 依赖性谷氨酰胺和 BBMV 和 BLMV 中的磷酸盐吸收。这些系统在基础状态下的表征将是其次是呼吸系统疾病期间的研究。高碳酸血症和未麻醉的动物会在一定时间内诱发低碳酸血症大型环境室。上述系统的适配每隔 1 小时检查一次近端酸化情况，诱发呼吸障碍后 1 天和 5 天。初步结果支持广泛的适应性变化近端酸化细胞系统的活性 4 天高碳酸血症或 5 天低碳酸血症后获得;值得注意的是，BLMV Na+-HCO3- 共转运没有改变高碳酸血症仅 1 小时后，也没有发生适应高碳酸血症 1 天后 BBMV Na+-H+ 交换器。这些研究可能为该机制提供重要的新见解和基础条件下近端酸化的调节以及 PaCO2 的急性和慢性变化期间。