Activation of the action potential Na+ ionophore of cultured neuroblastoma cells by veratridine and batrachotoxin

摘要: The activation of the action potential Na+ ionophore by veratridine and batrachotoxin is time- concentration-dependent completely reversible. Batrachotoxin acts more slowly than veratridine. concentration dependence at equilibrium suggests reversible interaction each toxin with a single class independent sites having dissociation constants physiologic ion concentrations 80 plus or minus 13 muM for 0.4 batrachotoxin. maximum velocity uptake 50 mM 128 12 nmol/min/mg in presence compared to 48 4 Treatment cells excess addition inhibits batrachotoxin-dependent 22-Na+ uptake. this inhibition that it reflects competitive displacement from its binding site inhibited manner divalent cations. cations exhibits significant specificity Mn-2+ greater Co-2+ Ni-2+ Ca-2+ Mg-2+ Sr-2+. (KI) are 0.84 veratridine-dependent 1.2 noncompetitive tetrodotoxin. apparent KD tetrodotoxin as 11 1 nM 150 approximately 8.5 Na+. Divalent do not affect A hypothesis presented which batrachotoxin, veratridine, interact an associated ionophore, whereas interacts physically functionally involved transport monovalent ionophore.