Delayed rectifier and Ca(2+)-dependent K(+) currents in human esophagus: roles in regulating muscle contraction.
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.
Wade
G R
GR
Department of Physiology, The University of Western Ontario, Canada.
Laurier
L G
LG
Preiksaitis
H G
HG
Sims
S M
SM
D015761:4-Aminopyridine / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D018999:Charybdotoxin / Q000494:pharmacology; D051668:Delayed Rectifier Potassium Channels; D004553:Electric Conductivity; D004947:Esophagus / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000166:cytology / Q000502:physiology; D010455:Peptides / Q000494:pharmacology; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019789:Tetraethylammonium / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
D051668:Delayed Rectifier Potassium Channels; D010455:Peptides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D018999:Charybdotoxin; D013779:Tetrodotoxin; D019789:Tetraethylammonium; C064719:iberiotoxin; D015761:4-Aminopyridine; D002118:Calcium