Studies on the Mechanisms of the Monofluoroacetanilides Poisoning to Mammals

Organophosphates, phosphorothioates, phosphorodithioates, phosphites, and phosphonates were found to inhibit the fluoroacetanilide amidohydrolase of chicken liver. Above all, the inhibition by triphenyl phosphate, tri-n-butyl phosphorothioate, triphenyl phosphite, Dipterex, and DDVP were extremely remarkable. Their concentrations for 50% inhibition were about 10^?8 m or 10^?7 m, and the inhibition of triphenyl phosphate was non-competitive to the substrate. These compounds were slightly or moderately toxic to mice even when administered intraperitoneally. The specificity of the inhibition was also discussed.

The effects of the fluoroacetanilide amidohydrolase (fluoroacetanilidase) inhibitors on the fluoroaceto-p-bromoanilide (FBA) poisoning to mammals and insects were studied. Triphenyl phosphate (TPP) and tri-n-butyl phosphorothioate (TBT) were mainly used as the inhibitors. TPP was effective for reducing the oral and cutaneous toxicities of FBA to mice and rats only when applied prior to the FBA application. However, in cases of the inhaled toxicity and the combined inhaled-cutaneous toxicity, TPP or TBT were effective even when they were applied simultaneously with FBA. When TPP and TBT were administered to mice by the combined inhaled-cutaneous application, the activity of fluoroacetanilidase in liver and kidney was rapidly decreased, but it recovered within 4 to 6 days after the application. The insecticidal and miticidal activities of FBA were not affected at all both in the previous and simultaneous applications of the inhibitors. However, it was found that the fluoroacetanilides hydrolyzing enzyme of Mealy plum aphid was not inhibited by TPP even in the concentration of 10^?4 m. The mechanisms of the fluoroacetanilides poisoning to mammals and insects were discussed.