AJP - Cell Physiology, Vol 259, Issue 5 C752-C761, Copyright © 1990 by American Physiological Society
Anion selectivity and block of the small-conductance chloride channel on pancreatic duct cells
M. A. Gray, C. E. Pollard, A. Harris, L. Coleman, J. R. Greenwell and B. E. Argent
Department of Physiological Sciences, University Medical School, Newcastle upon Tyne, United Kingdom.
Rat and human pancreatic duct cells have small-conductance Cl- channels in
their apical plasma membranes. These channels are regulated by secretin and
adenosine 3',5'-cyclic monophosphate and may function in parallel with
Cl(-)-HCO3- exchangers to allow HCO3- secretion from the duct cell. Using
the patch-clamp technique, we have now determined the anion permeability
sequence of the channel as NO3- greater than Br- approximately I-
approximately Cl- much greater than HCO3- much greater than gluconate. From
this we conclude 1) that anion permeation involves a weak interaction with
charged sites inside the channel pore, 2) that because of the low HCO3-/Cl-
permeability ratio it is unlikely that significant amounts of HCO3- could
be secreted directly via the channel, and 3) that channel permeability may
determine the anion selectivity of secretion. We also show that
5-nitro-2-(3-phenylpropylamino)benzoic acid blocks the small-conductance
Cl- channel, whereas 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid has
no effect.
