AJP - Gastrointestinal and Liver Physiology, Vol 262, Issue 2 369-G374, Copyright © 1992 by American Physiological Society
A large conductance K(+)-selective channel of guinea pig villus enterocytes is Ca2+ independent
G. M. Mintenig, A. S. Monaghan and F. V. Sepulveda
Agricultural and Food Research Council Institute of Animal Physiology and Genetics Research, Cambridge, United Kingdom.
The presence of K(+)-selective channels has been probed in enterocytes
isolated from guinea pig small intestinal villi by the patch-clamp
technique. A channel with a single-channel conductance of approximately 130
pS was observed in excised inside-out patches bathed in symmetrical K+. A
change in the K+ concentration in the intracellular aspect of the membrane
altered the current-voltage relationship as expected from the
constant-field equation when it is assumed that K+ is the only permeant
ion. A change in Cl- concentration was without effect. Neither the activity
of the channel nor its conductance was altered by addition of ATP or Ba2+
to the intracellular side of the patches. Changes in the free Ca2+
concentration were also without effect. The channel's open probability
showed no voltage dependence and appeared only occasionally active in
cell-attached patches where it had a linear current-voltage relation. The
K+ channel described, which cannot be readily classified in any of the
known classes of K+ channels, might provide an exit pathway for K+
recycling in guinea pig villus enterocytes.
