Paradoxical Effect of Congo Red on the Toxicity of Streptolysin S for Mice

摘要

The effect of congo red on the lethal action of streptolysin S has been investigated. The toxicity of mixtures containing congo red and a lethal dose of streptolysin S was found to be a function of the amount of dye used. When the amount was small (of the order of 1 μg), the mixtures possessed little or no toxicity; when large (100 μg), but far below the toxic dose of congo red alone, the mixtures invariably proved toxic. An hypothesis attempting to resolve the paradoxical observations is suggested.No protection was afforded mice by pre-treatment with congo red regardless of whether a small or a large dose was used. Binding of the dye by serum accounts for the failure of streptolysin S to be inhibited in vivo . A simple method of estimating the capacity of serum components to bind congo red is described.