Regulation of cell volume in a human biliary cell line: activation
of k+ and cl- currents.
Roman, Richard M., Yu Wang, and J. Gregory Fitz.
Division of Gastroenterology, Department of Medicine, Duke
University Medical Center, Durham, North Carolina, 27710
APStracts 3:0020G, 1996.
The mechanisms responsible for recovery from cell swelling were
evaluated in Mz-ChA-1 cells from human cholangiocarcinoma, a model
biliary cell line. Exposure to hypotonic buffer (40% less NaCl)
rapidly increased relative cell volume to 1.35 +/- 0.10 as measured
by a Coulter Multisizer, followed by regulatory volume decrease to
1.08 +/- 0.03 by 30 min. The same maneuver increased 86Rb (69 +/- 17
%) and 125I efflux (422 +/- 58 %) in cell monolayers. 86Rb efflux was
selectively inhibited by Ba2+ (IC50 1.5 mM), and 125I by 5-nitro-2
-(3-phenylpropylamino)-benzoic acid (NPPB) (IC50 50 [mu]M). Inhibition
of these conductive pathways partially inhibited recovery from
swelling. Membrane conductance measured by whole-cell patch clamp
analysis increased in 57/57 cells during swelling due to activation
of both K+ and Cl- conductances in most cells. K+ currents (75 % of
cells, 881 +/- 150 pA at 0 mV) were nearly linear and Ba2+-sensitive;
Cl- currents (70 % of cells, 2,696 +/- 244 pA at +60 mV) were
outwardly rectified, showed time-dependent inactivation at
depolarizing potentials, and were inhibited by NPPB. Chelation of
cytosolic Ca2+ decreased swelling-induced isotope efflux, prevented
activation of macroscopic K+ and Cl- currents, and blocked volume
recovery. These studies indicate that biliary cells are able to
regulate cell volume during osmotic stress by activation of separate
K+ and Cl- conductances through a mechanism which depends in part on
Ca2+-sensitive signaling pathways.
Received 1 September 1995; accepted in final form 16 January
1995.
APS Manuscript Number G387-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 January 96