Ionic channels in corneal endothelium.
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 K+ currents. One is due to an anion- and temperature-stimulated channel that is blocked by Cs+ but not by most other K+ channel blockers, and the other is similar to the family of A-currents found in excitable cells. The A-current is transient after a depolarizing voltage step and is blocked by both 4-aminopyridine and quinidine. These two currents are probably responsible for setting the -50 to -60 mV resting voltage reported for these cells. A Ca(2+)-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 G omega and have steady-state K+ currents that are approximately 10 pA at the resting voltage. Pairs or monolayers of cells are electrically coupled and dye coupled through gap junctions.
Rae
J L
JL
Department of Physiology and Biophysics and Ophthalmology, Mayo Foundation, Rochester, Minnesota 55905, USA.
Watsky
M A
MA
D000818:Animals; D018118:Chloride Channels / Q000502:physiology; D004594:Electrophysiology; D004728:Endothelium, Corneal / Q000378:metabolism*; D017629:Gap Junctions / Q000502:physiology; D006801:Humans; D007473:Ion Channels / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology; D015222:Sodium Channels / Q000502:physiology
D018118:Chloride Channels; D007473:Ion Channels; D015221:Potassium Channels; D015222:Sodium Channels