Toxicity and Anticholinesterase Activity of Halogenated Organophosphates to Boettcherisca peregrina12

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Abstract
The contact and injection toxicities of 8 halogenated OP insecticides: Ciba C-8874 (O-(2,5-dichloro-4-iodophenyl) O, O-diethyl phosphorothioate); C-11043 (O-(2,5-dichloro-4-iodophenyl) O, O-diethyl phosphate); Ciba C-11044 (O-(2,5-dichloro-4-iodophenyl) O-ethyl O-methyl phosphorothioate); Ciba C-18246 (O-(2,5-dichloro-4-iodophenyl) O-methyl methylphosphonothioate); Ciba C-14812 (O-(2,5-dichloro-4-iodophenyl) O-methyl ethylphosphonothioate) ; Ciba C-18244 (O- (2,5-dichloro-4-iodophenyI) O-ethyl ethylphosphonothioate); Ciba C-I7209 (O-(2,6-dichloro-4-iodophenyl) O, O-dimethyl phosphorothioate); and Ciba C-17210, (O-(2, 6-dichloro-4-iodophenyl) O, O- diethyl phosphorothioate) to female Boettcherisca peregrina (Robineau-Desvoidy) were investigated. The in vitro and in vivo anticholinesterase activities of these insecticides also were investigated. On the basis of the LD50 values, the order of contact toxicity of the insecticides was: C-11046 = C-11044 = C-8874 = C-11044 > C-18244 > C-17209 > C-17210 > C-14812; C-11046 > C-8874; C-11043 > C-11044; and the order of injection toxicity was: C-11043 = C-11046 > C-11044 > C-8874 > C-18244 > C-17209 > C-14812 > C-1710. Generally, the insecticides were slightly more toxic after injection than after topical application. The natural head cholinesterase activity as measured by the amount of head brei causing 80% hydrolysis of acetyl-choline chloride in 30 minutes was 6.0 mg. The high in vitro anticholinesterase activity of the phosphate C-11043 was comparable to its high contact and injection toxicity, but there was no correlation between toxicity and in vitro anticholinesterase activity of either the phosphorothioates or the phosphonothioates. Neither was there any correlation between toxicity and in vivo head cholinesterase inhibition. Head cholinesterase inhibition was more rapid after injection, and maximum inhibition was reached earlier than after topical application. In general, there was little or no reactivation of the cholinesterase.

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