Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States.
Department of Pediatrics and Human Development, College of Human Medicine, Michigan State University, Grand Rapids, Michigan, United States.
Am J Physiol Lung Cell Mol Physiol. 2024 Nov 1;327(5):L749-L755. doi: 10.1152/ajplung.00147.2024. Epub 2024 Sep 10.
In contrast to pig large airways, the pH of airway surface liquid (ASL) in pig small airways is regulated by CFTR-mediated HCO secretion and the vacuolar-type H ATPase (V-ATPase) proton secretion. We hypothesized that, in cystic fibrosis (CF), the ASL pH of small airways is acidic, and the V-ATPase is internalized. We quantified proton secretion during the addition of an alkaline test solution by measuring changes in a pH-dependent fluorescent dye generated by porcine small airway epithelia in the absence and presence of bafilomycin A1. The pH-dependent translocation of V-ATPase in ex vivo and in vivo preparations was measured using immunolocalization of V-ATPase. We found that bafilomycin-sensitive proton secretion stopped when the ASL pH was less than 7.10. In non-CF pigs and mice, we found that V-ATPase was localized in the apical membrane, and internalized when the lungs were instilled with a pH 6.8 solution. Studies in which we immediately fixed lungs from pigs revealed apical V-ATPase detection in non-CF piglets and less apical detection in CF piglets. Our data suggest that V-ATPase in small airways is internalized when the ASL pH is acidic. The decrease in apical localization of V-ATPase in CF pigs is consistent with an acidic ASL pH. In this study, we describe that vacuolar-type H ATPase (V-ATPase) internalizes when the airway surface liquid (ASL) pH in pig small airways is less than 7.10. Furthermore, we found that V-ATPase is not localized to the apical membrane in the small airways of newborn cystic fibrosis pigs.
与猪大气道相反，猪小气道的气道表面液体（ASL）的 pH 值受 CFTR 介导的 HCO3-分泌和液泡型 H+ATP 酶（V-ATPase）质子分泌调节。我们假设，在囊性纤维化（CF）中，小气道的 ASL pH 值呈酸性，并且 V-ATPase 被内化。我们通过测量猪小气道上皮在碱性测试溶液加入过程中 pH 依赖性荧光染料的变化来量化质子分泌，该变化由 bafilomycin A1 的存在和不存在引起。使用 V-ATPase 的免疫定位测量离体和体内制剂中 V-ATPase 的 pH 依赖性易位。我们发现，当 ASL pH 值小于 7.10 时，bafilomycin 敏感的质子分泌停止。在非 CF 猪和小鼠中，我们发现 V-ATPase 定位于顶膜，并且当用 pH 6.8 溶液灌注肺部时被内化。在我们立即从猪肺中固定的研究中，我们发现非 CF 仔猪的顶膜检测到 V-ATPase，而 CF 仔猪的顶膜检测到较少的 V-ATPase。我们的数据表明，当 ASL pH 值呈酸性时，小气道中的 V-ATPase 被内化。CF 猪中顶膜 V-ATPase 定位减少与 ASL pH 值呈酸性一致。在这项研究中，我们描述了当猪小气道的气道表面液体（ASL）pH 值小于 7.10 时，液泡型 H+ATP 酶（V-ATPase）会被内化。此外，我们发现 V-ATPase 不在新生 CF 猪小气道的顶膜上定位。
