MODULATION OF VOLTAGE-DEPENDENT INACTIVATION OF THE INWARDLY RECTIFYING K-T( CHANNEL BY CHLORAMINE)

The inwardly rectifying K+ channel (I-K1) exhibits voltage-dependent i nactivation at membrane voltages more negative than similar to -140 mV . The effect of chloramine-T on the inactivation of I-K1 was examined in guinea-pig ventricular myocytes using the patch-clamp technique. Ch loramine-T (2 mM) irreversibly inhibited the time-dependent decay of w hole-cell I-K1 inactivation. As a result, the negative slope region of the current-voltage (I-V) relationship was abolished. In cell-attache d single channel recordings, the number of active channels in the patc h decreased with time during the voltage-clamp step to the K+ equilibr ium potential (E(K)) of -100 mV. Chloramine-T prevented this time-depe ndent decrease in channel number, and ensemble averaged currents exhib ited abolishment of time-dependent decay of channel activity at E(K) - 100 mV. These results suggest that the hyperpolarization-induced inact ivation of cardiac I-K1 is controlled by voltage-dependent intrinsic g ating.