Mammals diazinon

The organophosphorons insecticides dimethoate and diazinon are mnch more toxic to insects (e.g., housefly) than they are to the rat or other mammals. A major factor responsible for this is rapid detoxication of the active oxon forms of these insecticides by A-esterases of mammals. Insects in general appear to have no A-esterase activity or, at best, low A-esterase activity (some earlier stndies confnsed A-esterase activity with B-esterase activity) (Walker 1994b). Diazinon also shows marked selectivity between birds and mammals, which has been explained on the gronnds of rapid detoxication by A-esterase in mammals, an activity that is absent from the blood of most species of birds (see Section 23.23). The related OP insecticides pirimiphos methyl and pirimiphos ethyl show similar selectivity between birds and mammals. Pyrethroid insecticides are highly selective between insects and mammals, and this has been attributed to faster metabolic detoxication by mammals and greater sensitivity of target (Na+ channel) in insects. 

Acute oral toxicity of diazinon to birds and mammals... 

Table 16.4 Acute Oral Toxicity of Diazinon to Birds and Mammals (All values shown are in milligrams of diazinon/kg body weight fatal to 50% after a single oral dose.)...

Diazinon is rapidly biotransformed and excreted in mammals. Estimated half-times of diazinon persistence were 6 to 12 h in rats (Anonymous 1972) and dogs (Iverson et al. 1975). Most of the diazinon metabolites were excreted in the urine as diethyl phosphoric add and diethyl phosphorothioic acid in dogs (Iverson et al. 1975), and as hydroxy diazinon and dehydrodiazinon in sheep (Machin et al. 1974). 

Diazinon is nonmutagenic to mammals, as judged by its inability to induce sister chromatid exchanges (SCE) in Chinese hamster ovary cells (CHOC) at 80 mg/kg culture medium. Most organophosphorus insecticides tested induced SCE in CHOC at this concentration (Nishio and... 

Table 16.8 Sublethal Effects of Diazinon in Selected Mammals... 

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