Antibodies against Tityus discrepans venom do not abolish the effect of Tityus serrulatus venom on the rat sodium and potassium channels

Anti-(Tityus serrulatus + Tityus bahiensis) and anti-Tityus discrepans veno m polyclonal antisera were used to investigate whether antigenic difference s exist between the venoms of the Brazilian T. serrulatus and the Venezuela n T. discrepans scorpions. Both antisera recognised the toxin-containing el ectrophoretic fractions of their cognate venoms and also those from Tityus zulianus and Tityus trinitatis venoms on Western blots. The anti-T. discrep ans antiserum reacted only weakly with T. serrulatus toxic polypeptides. Th e effect of T. serrulatus alpha- or beta-toxins on rat skeletal muscle Nachannels expressed in Xenopus laevis oocytes was abolished by pre-incubatin g the venom with anti-(T. serrulatus + T. bahiensis) serum but not with ant i-T. discrepans serum. Nor did the Brazilian or the Venezuelan sera prevent the reduction in K+ currents by T. serrulatus venom in X. laevis oocytes e xpressing the rat brain delayed rectifying Shaker K+ channel (Kv1.2). These results indicate that toxins from T. serrulatus and T. discrepans venoms, which primarily target mammalian Na+ channels, are antigenically distinct, although they probably share common epitopes. Our results also suggest that Na+ channel-active toxins are the immunodominant antigens of the T. serrul atus venom. (C) 1999 Elsevier Science Ltd. All rights reserved.