Abstract
Ba2+ and Ca2+ prevent and reverse the Btk δ-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.