A fast transient outward current in cultured cells from human pulmonary artery smooth muscle.
A voltage-dependent transient outward current (I(to)) was observed in cells cultured from human pulmonary artery smooth muscle when K+, but not Cs+, was the dominant cation in the pipette solution. In 30% of cells investigated using the Cs+ pipette solution, a tetrodotoxin-sensitive inward current (I(in)) dependent on extracellular Na+ was evoked from depolarizations positive to -30 mV.Iin showed voltage-dependent inactivation with a membrane potential at 50% of the evoked current (V50%) of -75.53 +/- 0.81 mV and slope factor potential (Vs) of -10.73 +/- 0.01 mV. In the presence of 1 microM tetrodotoxin, I(to) was rapidly evoked by depolarizations positive to -40 mV and decayed with a single exponential time course (tau = 9.9 +/- 1.1 ms, pulse potential = +50 mV). I(to) also showed voltage-dependent inactivation with a V50% of -70.9 +/- 2.63 mV and Vs of -7.7 +/- 0.03 mV. I(to) was inhibited concentration dependently by the K+ channel blocker, 4-aminopyridine (4-AP), with a concentration of 4-AP at which I(to) was reduced to 50% of control of 36.5 +/- 2.8 microM. These cells possess voltage-dependent currents characteristic of the K(+)-selective fast transient outward and Na(+)-selective inward currents of smooth muscle cells.
James
A F
AF
International Research Laboratories, Ciba-Geigy, Takarazuka, Japan.
Okada
T
T
Horie
M
M
D015761:4-Aminopyridine / Q000494:pharmacology; D000465:Algorithms; D002122:Calcium Chloride / Q000494:pharmacology; D002478:Cells, Cultured; D016009:Chi-Square Distribution; D005071:Evoked Potentials / Q000187:drug effects; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011189:Potassium Chloride / Q000494:pharmacology; D011651:Pulmonary Artery / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors
D013779:Tetrodotoxin; D011189:Potassium Chloride; D012964:Sodium; D015761:4-Aminopyridine; D002122:Calcium Chloride