The effects of ascorbic acid on diphtheria toxin and intoxicated HeLa cells.

Ascorbic acid (vitamin C) prevented diphtheria toxin from inhibiting the incorporation of [U-14C]-alanine into trichloroacetic acid precipitable material in HeLa cells. Ascorbic acid did not exhibit an effect on the adenosine diphosphate-ribosylation of amino acyl transferase II nor did it separate fragment A from fragment B in "nicked" toxin. A non-specific reducing agent, para-methylaminophenol sulfate, exhibited an effect on HeLa cells very similar to the results of ascorbic acid. Citric acid, a tricarboxylic acid, had no effect on HeLa cells.