Delayed rectifier potassium current (IK) in latent atrial pacemaker cells isolated from cat right atrium.
Whole-cell recording techniques were used to study the delayed rectifier K+ current (IK) in latent pacemaker cells isolated from cat right atrium. From a holding potential of -40 mV, depolarizing clamp steps elicited L-type Ca2+ current followed by an increasing outward current (IK). The time course of tail current amplitudes paralleled that of the time-dependent activation of outward current. Activation of IK exhibited a sigmoidal time course that was best fit by a power function where the activation variable was raised to the second power. The voltage-dependence of IK activation exhibited a sigmoidal relationship between -40 and +30 mV. The half-maximal activation voltage and slope factor were -21.9 +/- 1.3 and 13.8 +/- 0.9 mV respectively (n = 6). The fully activated I/V relationship of IK was linear between -100 and -30 mV and inwardly rectified at more positive voltages. Following IK activation, hyperpolarizations more negative than about -50 mV elicited tail currents that consisted of both IK deactivation and I(f) activation. A subtraction protocol was used to isolate IK tail currents. In 5.4 mM extracellular [K+], IK tail currents exhibited a reversal potential of -78.2 +/- 0.3 mV (n = 6). The reversal potential of IK was linearly related to log extracellular [K] and the slope was 51.5 mV per ten-fold change in extracellular [K]. At -70 mV, IK tail currents decayed as a single exponential function with a time constant of 159 +/- 16 ms (n = 6). These results indicate that latent atrial pacemakers exhibit IK activated by depolarization.(ABSTRACT TRUNCATED AT 250 WORDS)
Zhou
Z
Z
Loyola University of Chicago, Stritch School of Medicine, Department of Physiology, Maywood, IL 60153.
Lipsius
S L
SL
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D016275:Atrial Function; D001683:Biological Clocks; D002118:Calcium / Q000502:physiology; D002415:Cats; D004594:Electrophysiology; D005110:Extracellular Space / Q000378:metabolism; D005260:Female; D006321:Heart / Q000502:physiology*; D006325:Heart Atria / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000378:metabolism*
D015221:Potassium Channels; D011188:Potassium; D002118:Calcium