Ionic channels in corneal endothelium.
Rae, James L., Mitchell A. Watsky.
Department of Physiology and Biophysics and Ophthalmology, Mayo
Foundation, Rochester, MN 55905; and Department of Physiology and
Biophysics, University of Tennessee, Memphis, TN 38163
APStracts 2:0290C, 1995.
Single-channel patch clamp techniques as well as standard and
perforated-patch whole-cell voltage clamp techniques have been
applied to the study of ionic channels in the corneal endothelium of
several species. These studies have revealed two major potassium
currents. One is due to an anion- and temperature-stimulated channel
that is blocked by Cs but not by most other potassium channel
blockers, and the other is similar to the family of A-currents found
in excitable cells. The A-current is transient following a
depolarizing voltage step and is blocked by both 4-aminopyridine and
quinidine. These two currents are likely responsible for setting the
-50 to -60 mV resting voltage reported for these cells. A calcium
-activated, ATP-inhibited nonselective cation channel and a
tetrodotoxin-blocked Na+ channel are possible Na+ inflow pathways;
but, given their gating properties, it is not certain that either
channel works under physiological conditions. A large conductance
anion channel has also been identified by single-channel patch clamp
techniques. Single corneal endothelial cells have input resistances
of 5-10 gigohms and have steady-state potassium currents that are
about 10 pA at the resting voltage. Pairs or monolayers of cells are
electrically and dye-coupled through gap junctions.
Received 12 June 1995; accepted in final form 25 July 1995.
APS Manuscript Number C325-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 August 1995.