RESUMO
O,O,S-Trimethyl phosphorothioate, an impurity in several technical organophosphorus insecticides, when administered orally to rats at single doses as low as 15 mg/kg caused delayed mortality, with death occurring 4-22 d after treatment. Delayed toxic signs were also observed in mice, but mice were generally less sensitive than rats. O,O,S-triethyl phosphorothioate and O,S,S-trimethyl phosphorodithioate induced the same signs of intoxication at slightly higher doses. Rats treated with O,O,S-trimethyl phosphorothioate refused food and water within 24 h after treatment and did not eat or drink until the time of death. Neither injection of nutrient solution nor atropine served to reduce or block intoxication. However, the isomeric O,O,O-trimethyl phosphorothioate was a potent antagonist of the toxicity of O,O,S-trimethyl phosphorothioate. As little as 1% of the O,O,O-trimethyl isomer protected rats from the intoxicating effects of the O,O,S-trimethyl isomer at doses as high as 200 mg/kg. Rat serum carboxylesterase and cholinesterase were inhibited for prolonged periods after a single oral dose of O,O,S-trimethyl phosphorothioate, but the duration of inhibition was significantly less when the toxicant contained 1% O,O,O-trimethyl isomer.
Assuntos
Contaminação de Medicamentos , Inseticidas/toxicidade , Organotiofosfatos/toxicidade , Compostos Organotiofosforados/toxicidade , Animais , Atropina/farmacologia , Peso Corporal/efeitos dos fármacos , Hidrolases de Éster Carboxílico/antagonistas & inibidores , Inibidores da Colinesterase/toxicidade , Ingestão de Líquidos/efeitos dos fármacos , Ingestão de Alimentos/efeitos dos fármacos , Organotiofosfatos/farmacologia , Ratos , Ratos Endogâmicos , EstereoisomerismoRESUMO
The properties and actions of the bridged diphenyl acaricides are discussed. These pesticides, which are more or less structurally related to DDT, were the first of the specific acaricides to be developed. They exhibit remarkable properties of specificity, being primarily toxic to phytophagous mites but of very low toxicity to most nontarget species, including insects, fish, birds, and mammals. Although many important facets of their broad mode of action are understood, virtually nothing is known of their primary mode of action or the underlying bases of their specificities. In most ways they are model compounds for integrated control and pest management activities and thus merit greater attention than they have received to elucidate the fundamentals underlying their unusual properties and actions.
