Effect of pesticides mixture of dimethoate and methidathion on acetylcholinestrase during embryo development using chick embryo model

Pesticides mixture (dimethoate 30% and methidathion 40%) prepared by the farmers in Yemen and engaged in the cultivation of Qat, which is chewed by people every day including pregnant women. Therefore, the developing embryos in the society are more vulnerable than adults to the chronic cholinergic intoxication. This study aimed to examine the chronic effect of pesticides mixture on the AChE of developmental embryo in an avian model, which does not share the maternal potential confounds. For this, fresh fertile chicken eggs (Gallus gallus domesticus) were used. The lethal concentration of pesticides mixture for 50% killing (LD₅₀) values was computed on the basis of probit analysis and was found to be 40 ppm. 1/5^th LD₅₀ and 1/10^th LD₅₀ (8 and 4 ppm) were chosen to be the tested doses. Eggs weighing 54±1 gm were separated in to 3 batches of 10 eggs each batch. One batch of embryos was injected with normal saline and the other batches of embryos injected with pesticides mixture of 4 and 8 ppm each alternative day starting from incubation day 7 for 2 weeks. On day 21 after 12 hours of the last dose an amount of 200 µl blood was collected from the blood vessels surrounding the embryonic membranes and the heamolyzate was used for the assessment of the AChE activity calorimetrically. Result of this study indicated that 1/10^th of the LD₅₀ had only marginal effect on the AChE activity (40.6%). Whereas 1/5^th of the LD₅₀ of pesticides mixture caused significant inhibition of AChE activity (69%) which could not be reversible. So neuro-developmental consequences such as behavioral changes and memory impairment may prolong throughout the life span of the embryo.