Comparative efficacy of exogenous acetylcholinesterase administration on soman and dichlorvos toxicity in rats.

Cholinesterase (ChE) activity in the blood serum of rats was elevated to 15, 25, and 45 times by the sc administration of 1000, 2000 and 3000 electric eel acetylcholinesterase (AChE) units respectively. Apparently no ill-effect to animals was observed. The maximal activity of the enzyme occurred in 90 min after its administration and was directly proportional to the administered dose. The increase activity of ChE in the serum on the exogenous administration of AChE persisted for 18 hr. The exogenously raised serum ChE, protected rats against lethal dose of dichlorvos, but not against lethal dose of soman. The possible mechanism of differential response in discussed.

Effect of soman administration on beta-esterases in blood, liver microsomes and brain regions of rats.

Activities of enzymes cholinesterase (ChE) and carboxylesterase (CaE) were assayed in serum, liver microsomes and three regions of brain, viz; cerebrum, cerebellum and brain stem (with mid brain) in male albino rats at 0.5 and 2 h periods after administration of 1/2 LD 50 dose of soman (0.22 mg/kg) intraperitoneally in olive oil as vehicle. At 0.5 h, in serum, ChE activity declined to 33% of its initial level whereas CaE activity was almost completely inhibited. However, in the liver microsomes at this period, ChE activity was greatly inhibited (18% of initial level) whereas CaE activity was nearly unaffected. At 2 h period, both the enzymes in the serum were almost completely inhibited. In the brain regions (excepting in cerebellum), both the enzymes were nearly similarly inhibited (by 55% to 65% of the initial level) at both the periods. The time related differential response of these two beta-esterases in acute soman intoxication probably occurred in the peripheral tissues like blood and liver but not in the CNS.