Ionic channels in corneal endothelium

• Published in: The American journal of physiology Vol. 270; no. 4 Pt 1; pp. C975 - C989
• Main Authors: Rae, J L, Watsky, M A
• Format: Journal Article
• Language: English
• Published: United States 01-04-1996
• Subjects: Animals; Chloride Channels - physiology; Electrophysiology; Endothelium, Corneal - metabolism; Gap Junctions - physiology; Humans; Ion Channels - physiology; Potassium Channels - physiology; Sodium Channels - physiology
• ISSN: 0002-9513
• DOI: 10.1152/ajpcell.1996.270.4.c975

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.