The Journal of Membrane Biology

, Volume 135, Issue 3, pp 237–244 | Cite as

Redistribution of hepatocyte chloride during l-alanine uptake

  • Kening Wang
  • Robert Wondergem
Articles
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Revised:

Abstract

We used ion-sensitive, double-barrel microelectrodes to measure changes in hepatocyte transmembrane potential (Vm), intracellular K+, Cl-, and Na+ activities (aik, a Cl i and a Na i ), and water volume during l-alanine uptake. Mouse liver slices were superfused with control and experimental Krebs physiological salt solutions. The experimental solution contained 20 μml-alanine, and the control solution was adjusted to the same osmolality (305 mOsm) with added sucrose. Hepatocytes also were loaded with 50 mm tetramethylammonium ion (TMA+) for 10 min. Changes in cell water volume during l-alanine uptake were determined by changes in intracellular, steady-state TMA+ activity measured with the K+ electrode. Hepatocyte control Vm was -33±1 mV. l-alanine uptake first depolarized Vm by 2±0.2 mV and then hyperpolarized Vm by 5 mV to-38±1 mV (n = 16) over 6 to 13 min. During this hyperpolarization, a Na i increased by 30% from 19±2 to 25±3 mm (P < 0.01), and a K i did not change significantly from 83±3 mm. However, with added ouabain (1 mm) l-alanine caused only a 2-mV increase in Vm, but now a K i decreased from 61±3 to 54±5 mm (P < 0.05). Hyperpolarization of Vm by l-alanine uptake also resulted in a 38% decrease of a Cl i from 20±2 to 12±3 mm (P < 0.001). Changes in Vm and VCl — Vm voltage traces were parallel during the time of l-alanine hyperpolarization, which is consistent with passive distribution of intracellular Cl− with the Vm in hepatocytes. Added Ba2+ abolished the l-alanineinduced hyperpolarization, and a Cl i remained unchanged. Hepatocyte water volume during l-alanine uptake increased by 12±3%. This swelling did not account for any changes in ion activities following l-alanine uptake. We conclude that hepatocyte a K i is regulated by increased Na+-K+ pump activity during l-alanine uptake in spite of cell swelling and increased Vm due to increased K+ conductance. The hyperpolarization of Vm during l-alanine uptake provides electromotive force to decrease a Cl i . The latter may contribute to hepatocyte volume regulation during organic solute transport.

Key words

Liver l-alanine Chloride Cell volume regulation Membrane potential Ionsensitive microelectrodes 
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Copyright information

© Springer-Verlag New York Inc. 1993

Authors and Affiliations

  • Kening Wang
    • 1
  • Robert Wondergem
    • 1
  1. 1.Department of PhysiologyJames H. Quillen College of Medicine, East Tennessee State UniversityJohnson City

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