Sensitivity of volume-sensitive cl- conductance in human epithelial
cells to extracellular nucleotides.
Tsumura, Takehiko, Shigetoshi Oiki, Shunji Ueda, Minoru Okuma, and
Yasunobu Okada.
Department of Cellular and Molecular Physiology, National Institute
for Physiological Sciences, Okazaki 444, and Department of Internal
Medicine, Kyoto University Faculty of Medicine, Kyoto 606-01,
Japan
APStracts 3:0232C, 1996.
The sensitivity to extracellular nucleotides of volume-sensitive Cl-
channel activity was investigated by whole-cell and single-channel
patch-clamp recordings in a human small intestinal epithelial cell
line (Intestine 407) during steady osmotic swelling. Adenine
nucleotides added to the bathing solution suppressed whole-cell
volume-sensitive Cl- currents with the potency sequence of
ATP>ADP>AMP. In contrast, extracellular cAMP at over 0.1 mM
increased volume-sensitive Cl- currents in the entire voltage range
examined, whereas cGMP was without effect. Neither the single-channel
conductance nor the open probability was affected by extracellular
cAMP. Extracellular ATP (at over 30 (M), in the Mg-free form,
inhibited the whole-cell volume-sensitive Cl- current, preferentially
in the outward direction. By exposure to extracellular ATP, the
single Cl- channel current became flickery at positive potentials.
These results indicate that the volume-sensitive Cl- channel in the
human epithelial cell is voltage-independently stimulated by
extracellular cAMP but voltage-dependently blocked by the Mg-free
form of extracellular ATP.
Received 26 February 1996; accepted in final form 10 July 1996.
APS Manuscript Number C102-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 25 July 1996