Alpha-toxin permeabilized rat pheochromocytoma cells: a new approach to investigate stimulus-secretion coupling

The channel forming alpha-toxin of Staphylococcus aureus (about 50 micrograms/ml) markedly reduces the Ca2+ requirement for dopamine release by the rat pheochromocytoma cell line (PC 12). Maximal secretion by intact cells requires approximately 1 mM Ca2+, whereas release by alpha-toxin-permeabilized cells can already be triggered with microM concentrations of Ca2+. The latter process reaches a plateau at about 1 microM free Ca2+ and increases again with 10-20 microM free Ca2+. The sensitivity to low concentrations of Ca2+ indicates that the toxin, as a selective cell membrane permeabilizing agent, can be used as a powerful instrument to study stimulus-secretion coupling.