Cl- current in imcd cells activated by hypotonicity: time course,
atp dependence, and inhibitors.
Volk, Kenneth A., Chong Zhang, Russell F. Husted, and John B. Stokes.
Laboratory of Epithelial Transport, Department of Internal
Medicine, University of Iowa College of Medicine and Department of
Veterans Affairs Medical Center, Iowa City, Iowa 52242
APStracts 3:0071F, 1996.
The hypertonic environment of the renal medulla can change rapidly
according to the state of hydration of the animal. We used primary
cultures of rat IMCD cells to investigate the characteristics of Cl-
currents activated by an acute reduction in osmolarity (ICl(osm)).
Using the whole cell patch clamp technique we identified an outwardly
rectifying current that decayed slowly at strongly depolarizing
voltages. The onset of ICl(osm) began 6.7 min after the fall in bath
osmolarity, a delay longer than reported in other cell types.
Hypotonicity did not induce an increase in intracellular [Ca2+] and
activation of ICl(osm) did not require the presence of Ca2+.
Intracellular ATP was needed to evoke ICl(osm) when the hypotonic
stimulus was modest (50 mOsm/l or less), but was not necessary when
the stimulus was stronger (100 mOsm/l). ICl(osm) was inhibited by
NPPB but not by tamoxifen or glibenclamide. DIDS produced a voltage
-dependent block. Acute reduction in osmolarity using cells grown on
filters did not induce a Cl- secretory current. The ICl(osm) of IMCD
cells appears to be on the basolateral membrane and displays some
unique features.
Received 12 October 1995; accepted in final form 29 March 1996.
APS Manuscript Number F347-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 16 April 96