BETA-SCORPION TOXIN-2 FROM CENTRUROIDES NOXIUS BLOCKS VOLTAGE-GATED K+ CHANNELS IN HUMAN-LYMPHOCYTES

Using the patch-clamp technique, we determined that P-scorpion toxin 2 from Centruroides noxius Hoffmann decreased whole-cell n-type K+ currents in human peripheral blood lymphocytes, with a half blocking concentration of approx. 5 mu M. Toxin-2-accelerated inactivation, however,did not influence the kinetics of activation of the K+ conductance. The percentage increase in K+ channel inactivation rate and the degree of drug-induced block was independent of membrane potential. K+ channel block by Toxin 2 was instantaneous, not removable by washing with drug free extracellular solution. However, 10 mg/ml BSA in the bath lifted the toxin-induced block almost instantaneously and completely. Flow cytometric membrane potential measurements with the oxonol dye showed that Toxin 2 depolarizes human lymphocytes in concert with its K+ channel blocking effect. (C) 1995 Academic Press, Inc.