Barium and calcium block Bacillus thuringiensis subspecies Kurstaki delta-endotoxin inhibition of potassium current across isolated midgut of larval Manduca sexta.

Ba2+ and Ca2+ prevent and reverse the Btk delta-endotoxin inhibition of the short-circuit current in isolated lepidopteran midgut. These findings support the K+ pump-leak steady-state model for midgut K+ homeostasis and the K+ channel mechanism of Bt toxin action. They provide a new tool with which to study the interactions between Bt toxin and midgut cell membranes.