Af. James et al., A FAST TRANSIENT OUTWARD CURRENT IN CULTURED-CELLS FROM HUMAN PULMONARY-ARTERY SMOOTH-MUSCLE, American journal of physiology. Heart and circulatory physiology, 37(6), 1995, pp. 2358-2365
A voltage-dependent transient outward current (I-to) was observed in c
ells cultured from human pulmonary artery smooth muscle when K+, but n
ot Cs+, was the dominant cation in the pipette solution. In 30% of cel
ls investigated using the Cs+ pipette solution, a tetrodotoxin-sensiti
ve inward current (I-in) dependent on extracellular Na+ was evoked fro
m depolarizations positive to -30 mV. I-in showed voltage-dependent-in
activation with a membrane potential at 50% of the evoked current (V-5
0%) of -75.53 +/- 0.81 mV and slope factor potential (V-s) of -10.73 /- 0.01 mV. In the presence of 1 mu M tetrodotoxin, I-to was rapidly e
voked by depolarizations positive to -40 mV and decayed with a single
exponential time course (tau = 9.9 +/- 1.1 ms, pulse potential = +50 m
V). I-to also showed voltage-dependent inactivation with a V-50% of -7
0.9 +/- 2.63 mV and V-s of -7.7 +/- 0.03 mV. I-to was inhibited concen
tration 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 cont
rol of 36.5 +/- 2.8 mu M. These cells possess voltage-dependent curren
ts characteristic of the K+-selective fast transient outward and Na+-s
elective inward currents of smooth muscle cells.