Volume-sensitive purinergic signaling in human hepatocytes

Andrew P. Feranchak, J. Gregory Fitz, Richard M. Roman

Research output: Contribution to journalArticle

88 Scopus citations

Abstract

Background/Aims: Purinergic signaling potentially contributes to many liver functions. Therefore, the purpose of these studies was to characterize adenosine 5'-triphosphate (ATP) release from human hepatocytes, and to determine the role of extracellular ATP in the autocrine regulation of Cl- permeability and cell volume homeostasis. Methods: Release of ATP (luciferase-luciferin assay), Cl- currents (whole-cell patch clamp), and cell volume (Coulter Multisizer) were measured in human hepatocytes within 12 h of isolation. Results: Hepatocyte swelling increased bioluminescence from basal values of 11.21 ± 0.45 to 178.29 ± 44.49 and 492.15 ± 89.41 arbitrary light units following 20 and 40% buffer dilutions, respectively (p<0.001), representing an increase in extracellular ATP from ~10 to >300 nM. Whole-cell Cl- currents activated during exposure to hypotonic buffer (15% less mosmol, 126.34 ± 36.49 pA/pF) and ATP (10 μM, 71.92 ± 15.48 pA/pF) exhibited outward rectification, time-dependent inactivation at depolarizing potentials, and sensitivity to the anion channel blocker 5- nitro-2-(3-phenylpropylamino)benzoic acid (NPPB). Removal of extracellular ATP (apyrase) prevented volume-sensitive current activation. Exposure to hypotonic buffer (30% less mosmol) increased mean relative volume to 1.092 ± 0.004 by 2.5 min, and volume recovery (1.019 ± 0.002 by 30 min) was abolished by NPPB, apyrase, and the P2 receptor antagonist suramin. Conclusions: These findings indicate that human hepatocytes exhibit constitutive and volume-dependent ATP release, which is a critical determinant of membrane Cl- permeability and cell volume regulation. ATP release may represent an extracellular signaling pathway that couples the cellular hydration state to important hepatic functions.

Original languageEnglish (US)
Pages (from-to)174-182
Number of pages9
JournalJournal of Hepatology
Volume33
Issue number2
DOIs
StatePublished - Aug 2000

Keywords

  • Cl channel
  • Hepatocyte
  • Luminescence
  • P2 receptor
  • Purinergic
  • Volume

ASJC Scopus subject areas

  • Hepatology

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