Redistribution of hepatocyte chloride during L-alanine uptake.
We used ion-sensitive, double-barrel microelectrodes to measure changes in hepatocyte transmembrane potential (Vm), intracellular K+, Cl-, and Na+ activities (aiK, aiCl and aiNa), 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 mM L-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, aiNa increased by 30% from 19 +/- 2 to 25 +/- 3 mM (P < 0.01), and aiK 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 aiK 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 aiCl 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.(ABSTRACT TRUNCATED AT 250 WORDS)
Wang
K
K
Department of Physiology, James H. Quillen College of Medicine, East Tennessee State University, Johnson City 37614-0576.
Wondergem
R
R
D000409:Alanine / Q000493:pharmacokinetics* / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D001692:Biological Transport / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure; D002712:Chlorides / Q000378:metabolism*; D008099:Liver / Q000166:cytology* / Q000378:metabolism* / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D008813:Mice, Inbred ICR; D008839:Microelectrodes; D009994:Osmolar Concentration; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology; D014882:Water-Electrolyte Balance
D002712:Chlorides; D000644:Quaternary Ammonium Compounds; D001464:Barium; D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; C027917:tetramethylammonium; D000409:Alanine; D011188:Potassium