Potassium current in clonal cytotoxic T lymphocytes from the mouse

The electrical properties of the cell membrane of clonal cytotoxic T lymphocytes in the mouse were studied by using the whole cell variation of the patch electrode voltage-clamp technique. Outward currents were activated with an exponential time course of several milliseconds time constant when the membrane potential was made more positive than -50 to -40 mV. This current is not activated as a result of Ca2+ entry. The estimated reversal potential of the current indicates that the current is predominantly carried by K+. The activation kinetics depend only on membrane potential, not on [K+]0. The amplitude of the current decreases exponentially with time constants of several hundred milliseconds during a maintained voltage pulse, due mainly to a decrease in conductance. Recovery from inactivation roughly followed a single exponential time course with a time constant of tens of seconds; this time constant depended upon not only the membrane potential but also the amount of initial inactivation. The current is suppressed by quinidine and tetraethylammonium, their half-suppression concentrations being 23 microM and 14 mM respectively. An increase of the outward current is suggested to be associated with the lethal hit of the cytotoxic reaction.