Inhibition of viral interferon induction in mammalian cell cultures by azo dyes and derivatives activated with rat liver S9 fraction.

Four azo dyes (Benzopurpurine 4B, trypan blue, Direct Blue 15, and Congo red) and their derivatives (o-tolidine, o-dianisidine, and benzidine) were studied for their effect on induction of interferon by influenza virus in mammalian, Rhesus monkey kidney (LLC-MK2), cell monolayers. Whereas Benzopurpurine 4B, Direct Blue 15, and Congo red inhibited viral interferon induction from approximately 35 to 60%, negligible inhibition was noted with trypan blue and other derivative compounds. By comparison, when rat S9 fraction was used for enzymatic activation of azo dyes and derivatives, interferon inhibition was significantly depressed moreover (P less than 0.01 to less than 0.0001) by all chemical compounds. The concentration of rat S9 (0.5%) used for metabolic activation of dyes and congeners was critical because concentrations greater than 0.5% of S9 per se inhibited the interferon induction process. Uninduced hamster S9 and both Aroclor 1254-induced hamster and rat S9 fractions were all comparable in their ability to activate the chemical compounds tested. That potential mutagenic and carcinogenic chemicals which require metabolic activation can be discriminated on the basis of interferon induction inhibition in eukaryotic cell cultures augurs for the usefulness and credibility of this system.