Voltage-gated potassium currents in rat vas deferens smooth muscle cells.
Voltage-gated components of the outward current in single smooth muscle cells isolated from the epididymal part of the rat vas deferens were studied using amphotericin B perforated patch-clamp techniques. The complex kinetics of the net outward current elicited by positive voltage steps from -80 mV to +40 mV suggested the presence of several components. Bath application of 200 nM charybdotoxin, a potent blocker of large-conductance, Ca(2+)-dependent K(+) channels (BK(Ca)), reduced the current amplitude significantly. When BK(Ca) channels were suppressed, fast-inactivating (I(K,f)) and delayed rectifying (I(K,dr)) components of the outward current were identified. I(K,f) was characterized by fast kinetics of current decay, negative steady-state activation and inactivation dependencies and sensitivity to 4-aminopyridine with an apparent K(d) of 0.32 mM, properties similar to those of the A-type K(+) current. In contrast, I(K,dr) activated and inactivated at more positive potentials. The time constant of activation of I(K,dr) was voltage dependent with an e-fold decrease per 21 mV depolarization. I(K,dr) was inhibited by clofilium, a blocker of voltage-gated K(+) channels, with an IC(50) of 12 micro M and was not blocked by 5 mM 4-aminopyridine. The possible significance of the voltage-gated currents is discussed.
Harhun
Maksym I
MI
Nerve-Muscle Physiology Department, Bogomoletz Institute of Physiology, Bogomoletz Street 4, Kiev-24, Ukraine.
Jurkiewicz
Aron
A
Jurkiewicz
Neide H
NH
Kryshtal
Dmytro O
DO
Shuba
Michael F
MF
Vladimirova
Irina A
IA
D015761:4-Aminopyridine / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D018999:Charybdotoxin / Q000494:pharmacology; D051668:Delayed Rectifier Potassium Channels; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008297:Male; D008954:Models, Biological; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology; D024681:Potassium Channels, Calcium-Activated / Q000037:antagonists & inhibitors; D024642:Potassium Channels, Voltage-Gated / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D019789:Tetraethylammonium / Q000494:pharmacology; D014649:Vas Deferens / Q000166:cytology / Q000378:metabolism*
D051668:Delayed Rectifier Potassium Channels; D051036:Large-Conductance Calcium-Activated Potassium Channels; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D024642:Potassium Channels, Voltage-Gated; D018999:Charybdotoxin; D019789:Tetraethylammonium; D015761:4-Aminopyridine