Anion requirement and effect of anion transport inhibitors on the response of vero cells to diphtheria toxin and modeccin

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Abstract
The anion requirement for toxic action of diphtheria toxin and modeccin was studied. In Cl−-free Hepes buffer made isotonic with mannitol, cells were insensitive to diphtheria toxin and modeccin. Just 2 mM NaCl was sufficient to obtain full toxic activity of modeccin, whereas 140 mM NaCl was required for maximal intoxication with diphtheria toxin. Br− could substitute for Cl−. NO3−, I− and ClO3− were less efficient than Cl−, whereas SO42− and SCN− were unable to replace Cl−. Cl− deprivation both reduced the ability of cells to bind diphtheria toxin and prevented bound toxin from intoxicating the cells. The binding of modeccin was not reduced. SITS (4-acetamide-4′-isothio-cyano-stilbene-2,2′-disulfonic acid), an inhibitor of Cl− entry, protected against diphtheria toxin and modeccin, indicating that Cl− transport is required for intoxication.