title: Intracellular acidification increases adenosine transport in human umbilical vein endothelial cells.
abstract: Adenosine is taken up via human equilibrative nucleoside transporters 1 (hENT1) and 2 (hENT2) at a physiological extracellular pH (pHo ∼7.4) in human umbilical vein endothelial cells (HUVECs). Acidic pHo increases the uptake of adenosine and 5-hydroxytryptamine (5HT) via hENT4 in this cell type. However, modulation of hENT1 and hENT2 transport activity by the pHi is unknown. We investigated whether hENT1 and hENT2-adenosine transport was regulated by acidic pHi.
  
  
  
  HUVECs loaded with a pH sensitive probe were subjected to 0.1-20 mmol/L NH4Cl pulse assay to generate 6.9-6.2 pHi. Before pHi started to recover, adenosine transport kinetics (0-500 μmol/L, 37 °C) in the absence or presence 1 or 10 μmol/L S-(4-nitrobenzyl)-6-thio-inosine (NBTI), 2 mmol/L hypoxanthine, 2 mmol/L adenine, 100 μmol/L 5HT, or 500 μmol/L adenosine, was measured.
  
  
  
  Overall adenosine transport (i.e., hENT1+hENT2) was semisaturable and partially inhibited by 1 μmol/L, but abolished by 10 μmol/L NBTI in cells non-treated or treated with NH4Cl. The initial velocity and non-saturable, lineal component for overall transport were increased after NH4Cl pulse. hENT1 and hENT2-mediated adenosine transport maximal capacity was increased by acidic pHi. hENT1 activity was more sensitive than hENT2 activity to acidic pHi.
  
  
  
  hENT1 and hENT2-adenosine transport is differentially regulated by acidic pHi in HUVECs. These findings are important in pathologies associated with pHi alterations such as gestational diabetes mellitus.
authors.affiliation: Cellular and Molecular Physiology Laboratory (CMPL), Division of Obstetrics and Gynaecology, School of Medicine, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago 8330024, Chile; Department of Education, Faculty of Education, Universidad de Antofagasta, Antofagasta 1270300, Chile.
authors.forename: Natalia
authors.initials: N
authors.lastname: Celis
authors.affiliation: Cellular and Molecular Physiology Laboratory (CMPL), Division of Obstetrics and Gynaecology, School of Medicine, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago 8330024, Chile.
authors.forename: Joaquín
authors.initials: J
authors.lastname: Araos
authors.affiliation: Cellular and Molecular Physiology Laboratory (CMPL), Division of Obstetrics and Gynaecology, School of Medicine, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago 8330024, Chile.
authors.forename: Carlos
authors.initials: C
authors.lastname: Sanhueza
authors.affiliation: Cellular and Molecular Physiology Laboratory (CMPL), Division of Obstetrics and Gynaecology, School of Medicine, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago 8330024, Chile; Department of Basic Sciences, Faculty of Sciences, Universidad del Bío-Bío, Chillán 3780000, Chile.
authors.forename: Fernando
authors.initials: F
authors.lastname: Toledo
authors.affiliation: Department of Education, Faculty of Education, Universidad de Antofagasta, Antofagasta 1270300, Chile; Biomedical Department, Faculty of Health Sciences, Universidad de Antofagasta, Antofagasta 1270300, Chile.
authors.forename: Ana R
authors.initials: AR
authors.lastname: Beltrán
authors.affiliation: Cellular and Molecular Physiology Laboratory (CMPL), Division of Obstetrics and Gynaecology, School of Medicine, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago 8330024, Chile; Metabolic Diseases Research Laboratory, Center of Research, Development and Innovation in Health - Aconcagua Valley, San Felipe Campus, School of Medicine, Faculty of Medicine, Universidad de Valparaíso, San Felipe 2172972, Chile.
authors.forename: Fabián
authors.initials: F
authors.lastname: Pardo
authors.affiliation: Cellular and Molecular Physiology Laboratory (CMPL), Division of Obstetrics and Gynaecology, School of Medicine, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago 8330024, Chile.
authors.forename: Andrea
authors.initials: A
authors.lastname: Leiva
authors.affiliation: Cellular and Molecular Physiology Laboratory (CMPL), Division of Obstetrics and Gynaecology, School of Medicine, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago 8330024, Chile; Biomedical Department, Faculty of Health Sciences, Universidad de Antofagasta, Antofagasta 1270300, Chile. Electronic address: marco.ramirez@uantof.cl.
authors.forename: Marco A
authors.initials: MA
authors.lastname: Ramírez
authors.affiliation: Cellular and Molecular Physiology Laboratory (CMPL), Division of Obstetrics and Gynaecology, School of Medicine, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago 8330024, Chile; Department of Physiology, Faculty of Pharmacy, Universidad de Sevilla, Seville E-41012, Spain; University of Queensland Centre for Clinical Research (UQCCR), Faculty of Medicine and Biomedical Sciences, University of Queensland, Herston, QLD 4029, Queensland, Australia. Electronic address: sobrevia@med.puc.cl.
authors.forename: Luis
authors.initials: L
authors.lastname: Sobrevia
mesh_terms: D000241:Adenosine / Q000378:metabolism* / Q000494:pharmacology; D001692:Biological Transport; D033721:Equilibrative Nucleoside Transporter 1 / Q000378:metabolism*; D033722:Equilibrative-Nucleoside Transporter 2 / Q000378:metabolism*; D005260:Female; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D011247:Pregnancy; D013868:Thioinosine / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D033721:Equilibrative Nucleoside Transporter 1; D033722:Equilibrative-Nucleoside Transporter 2; C438649:SLC29A1 protein, human; C438654:SLC29A2 protein, human; D013868:Thioinosine; C001789:4-nitrobenzylthioinosine; D000241:Adenosine
keywords: Adenosine transport; ENT transporters; Endothelium; Foetus; Intracellular pH