Referenced in: none

Automatically associated channels: Kv1.2 , Kv1.5

Title: Delayed rectifier and Ca(2+)-dependent K(+) currents in human esophagus: roles in regulating muscle contraction.

Authors: G R Wade, L G Laurier, H G Preiksaitis, S M Sims

Journal, date & volume: Am. J. Physiol., 1999 Oct , 277, G885-95

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/10516156

Abstract
We have examined K(+) channels and their function in human esophageal smooth muscle using perforated patch recording, RT-PCR to identify channel mRNA, and muscle contraction to study the effects of channel blockers. Depolarization revealed at least two types of currents: a 4-aminopyridine (4-AP)-sensitive transient delayed rectifier K(+) (K(V)) and a Ca(2+)-dependent K(+) (K(Ca)) current. K(Ca) current was active at positive potentials and was blocked by tetraethylammonium (TEA), iberiotoxin, and charybdotoxin but was insensitive to 4-AP. The mRNA encoding the gene products of Kv1.2 and Kv1.5 was identified in muscle and dissociated cells, consistent with these channel types contributing to K(V) current. 4-AP increased resting tension of muscle strips, suggesting a role for K(V) in setting the membrane potential. TEA, but not 4-AP, augmented the amplitude and duration of electrically evoked contraction, effects that were abolished by nifedipine. Here we provide the first description of macroscopic K(+) currents in human esophagus. K(V) channels participate in regulation of resting tension, whereas the K(Ca) channel limits depolarization and contraction during excitation.