Single Channel Analysis of the Inward Rectifier K Current in the Rabbit Ventricular Cells (original) (raw)

Abstract

The inward rectifier K channel in rabbit ventricular cells was studied by the patch-clamp method. Single channel currents were recorded in giga-sealed cell-attached patches with 150mM K+ in the pipette. The slope conductance in the membrane potential range from -140 to -40mV was 46.6±6.7pS (mean±S.D., _n_=16), and was reduced by decreasing [K+] in the pipette (20 or 50mM). The channel was blocked by an application of Cs+ or Ba2+ (0.04-1mM) in the pipette. Outwardly directed current, recorded with 50mM K+ in the pipette, revealed the inward rectification of the single channel current. The probability of the channel being open was 0.33±0.05 (_n_=10) at the resting potential (RP=-81.7±1.7mV, n=16) with 150mM K+ in the pipette, and it decreased with hyperpolarization. The mean open time of the channel was 178±25msec (_n_=6) at RP. The closed time of the channel seemed to have two exponential components, with time constants of 11.0±2.0msec and 1.92±0.52sec (_n_=6) at RP. The slower time constant was increased with hyperpolarization. The averaged patch current recorded upon hyperpolarizing pulses demonstrated a time-dependent current decay as expected from the single channel kinetics. The results indicated that the inward rectifier K+ current has time- and voltage-dependent kinetics.