IMMUNOSUPPRESSORS INHIBIT VOLTAGE-GATED POTASSIUM CHANNELS IN HUMAN PERIPHERAL-BLOOD LYMPHOCYTES

The effects of immunosuppressive agents on the potassium current of hu man peripheral blood lymphocytes have been studied using the whole-cel l patch-clamp technique. Cyclosporin A(10 mu g/ml), rapamycin (10 mu g /ml) and FK-506 (2.5 mu g/ml) reduced the peak K+ current by approxima tely 40, 30 and 40% of the control, respectively, without any change i n the reversal potential of the current. The current inhibition was si milar at all membrane potentials studied and was accompanied with an i ncrease in the rate of K+ current inactivation Membrane potential meas urements in current-clamp showed a marked depolarization of the membra ne (>10 mV) upon the addition of either immunosuppressor to the cells. Our findings revealed that the voltage-dependent potassium current in human peripheral blood lymphocytes is inhibited by Cyclosporin A and other immunosuppressors, resulting in a depolarized membrane potential . (C) 1996 Academic Press, Inc.