[Characterization of outward current in mouse ventricular myocytes].
Depolarization-activated, calcium-independent outward currents (Iout) in enzymatically dispersed mouse ventricular myocytes were characterized by whole-cell recording technique. During brief depolarizations to potentials positive to -50 mV, outward K+ currents in these cells rise rapidly to a peak followed by a slower decay to an apparent plateau. The relative peak to plateau amplitudes in a single cell varied as a function of the holding potential (HP) from which the currents were evoked. Reversal potentials for the peak and plateau components were -64.3 +/- 3.9 mV and -53.3 +/- 2.9 mV, respectively (uncorrected for junction potentials). The outward current decay is well described by double exponential fits, whereas the time course of peak Iout decay following a 500 ms prepulse is best fitted by single exponential function, indicating the presence of two distinct components, IKf and IKs, of the outward currents in mouse ventricular cells. Application of 4-AP were accompanied by a marked attenuation of peak Iout and plateau Iout, indicating that both IKf and IKs display similar sensitivities to 4-AP. The steady state inactivation of IKf is found incomplete within the test potential range (-80 - +30 mV) owing probably to the fact that the APD of mouse myocardium is too short.
Zhou
J
J
National Key Laboratory of Biomembrane and Membrane Bioengineering, Peking University, Beijing.
Hoa
X M
XM
Wang
Z M
ZM
Jin
M W
MW
Qian
J Q
JQ
Liu
T F
TF
D000818:Animals; D004594:Electrophysiology; D006321:Heart / Q000502:physiology*; D051379:Mice; D009206:Myocardium / Q000166:cytology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology*
D015221:Potassium Channels