%0 Journal Article
%T The V©\ATPase is expressed in the choroid plexus and mediates cAMP©\induced intracellular pH alterations
%A Dagne Barbuskaite
%A Dennis Brown
%A Helle H. Damkier
%A Henriette L. Christensen
%A Jeppe Praetorius
%A Teodor G. P£¿unescu
%A Vladimir Matchkov
%J Archive of "Physiological Reports".
%D 2017
%R 10.14814/phy2.13072
%X The cerebrospinal fluid (CSF) pH influences brain interstitial pH and, therefore, brain function. We hypothesized that the choroid plexus epithelium (CPE) expresses the vacuolar H+©\ATPase (V©\ATPase) as an acid extrusion mechanism in the luminal membrane to counteract detrimental elevations in CSF pH. The expression of mRNA corresponding to several V©\ATPase subunits was demonstrated by RT©\PCR analysis of CPE cells (CPECs) isolated by fluorescence©\activated cell sorting. Immunofluorescence and electron microscopy localized the V©\ATPase primarily in intracellular vesicles with only a minor fraction in the luminal microvillus area. The vesicles did not translocate to the luminal membrane in two in vivo models of hypocapnia©\induced alkalosis. The Na+©\independent intracellular pH (pHi) recovery from acidification was studied in freshly isolated clusters of CPECs. At extracellular pH (pHo) 7.4, the cells failed to display significant concanamycin A©\sensitive pHi recovery (i.e., V©\ATPase activity). The recovery rate in the absence of Na+ amounted to <10% of the pHi recovery rate observed in the presence of Na+. Recovery of pHi was faster at pHo 7.8 and was abolished at pHo 7.0. The concanamycin A©\sensitive pHi recovery was stimulated by cAMP at pH 7.4 in vitro, but intraventricular infusion of the membrane©\permeant cAMP analog 8©\CPT©\cAMP did not result in trafficking of the V©\ATPase. In conclusion, we find evidence for the expression of a minor fraction of V©\ATPase in the luminal membrane of CPECs. This fraction does not contribute to enhanced acid extrusion at high extracellular pH, but seems to be activated by cAMP in a trafficking©\independent manner
%K BCECF fluorometry
%K cerebrospinal fluid
%K fluorescence©\activated cell sorting
%K pH regulation
%U https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5256157/