Spontaneous reactivation and aging kinetics of acetylcholinesterase inhibited by dichlorvos and diazinon.

Organophosphorus (OP) are among the most toxic of all substances that cause poisoning in food animals and are the most frequently encountered insecticides, commonly detected in agricultural products, animal-derived foodstuffs, environmental samples, and home use and represent a significant potential health risk. The first-order rate constants obtained for spontaneous reactivation (k(s)) was found to be higher in sheep compared to cattle, pig, and ranged between 0.133 to 0.323 hr⁻¹ and between 0.021 to 0.088 hr⁻¹ for dichlorvos (DDVP) and diazinon (DZN) respectively. Aging of phosphorylated acetylcholinesterase (AChE) follows the kinetics of a first-order reaction with rate constants of aging (k(a)) higher in cattle compared to sheep and pig, and ranged between 0.013 to 0.021 hr⁻¹ and between 0.009 to 0.01 hr⁻¹ for DDVP and DZN respectively. Half-time (t½) for spontaneous reactivation and aging are higher in DZN compared to DDVP and ranged from 2.3 to 85.3 hr (sheep), 3.2 to 76.3 hr (cattle), and 2.9 to 58.3 hr (pig), respectively.