Sodium uptake associated with activation of action potential ionophores of cultured neuroblastoma and muscle cells.

Veratridine, an activator of action potential Na(+) ionophores, stimulated passive Na(+) uptake by electrically excitable neuroblastoma and muscle cells but had no effect on clonal cell lines defective in Na(+)-ionophore activity. Veratridine-dependent Na(+) uptake was completely inhibited by tetrodotoxin, a specific inhibitor of the action potential Na(+) ionophore. Half-maximal inhibition was obtained with 11 nM tetrodotoxin. Thus, veratridinedependent Na(+) uptake provides a specific and convenient means of assaying populations of cultured cells for action potential Na(+)-ionophore activity.