In vitroinhibition of plasma and brain cholinesterases of growing chicks by chlorpyrifos and dichlorvos

Abstract

This study assessed in vitro inhibition of plasma and brain cholinesterases (ChE) by the organophosphate insecticides chlorpyrifos and dichlorvos in chicks at ages of 2, 10, 20 and 30 days. Plasma samples and whole-brain homogenates of each age group were pooled and ChE activity was determined by an electrometric method with or without the organophosphate (0.5 and 1.0 µM). ChE inhibitions were the highest in 2-and 10-day-old chicks (20-83%), followed by 5-73% inhibitions at ages of 20 and 30 days. Cholrpyrifos decreased plasma ChE activity only at the ages of 2 and 10 days by 21-75%. Dichlorvos decreased plasma ChE activity at all the ages tested (2-30 days) by 39-83%. The highest percentage of plasma ChE inhibition by chlorpyrifos and dichlorvos was in 2-day-old chicks. In the brain homogenate, chlorpyrifos decreased the ChE activity between ages 2 and 20 days by 20-62%. The highest percentage of brain ChE inhibition occurred at the age of 10 days and the least was at 20 and 30 days. Dichlorvos decreased brain ChE activity between ages 2 and 20 days by 24-74%. At the age of 30 days, only the higher concentration of dichlorvos (1 µM) decreased brain ChE activity by 27%. The data suggest an age-related differential in vitro inhibition of plasma and brain ChE s in chicks. In vitro ChE inhibition, though it does not exclude interfering factors, could be useful for initial screening of the inhibitory actions of organophosphate insecticides in chickens.

A meta-analysis of normal human blood cholinesterase activities determined by a modified electrometric method

“…One of these methods is a modified electrometric determination of blood ChE activity reported in men [ 28 – 30 ]. The method has also been used in various animal species with different incubation times of the enzymatic reaction medium for monitoring in vivo and in vitro blood ChE inhibitions induced by organophosphates and carbamate insecticides [ 28 , 31 – 37 ].…”

In Vitro Inhibition of Blood Cholinesterases by the Organophosphate Dichlorvos in Typ-2 Diabetic Patients

“…This finding correlates with previous reports on in vitro inhibitory effects of organophosphates on blood cholinesterases. [25][26][27] However, the percentages of plasma and erythrocyte ChE inhibitions in type-2 diabetic patients were higher than those of respective control values (Table 2). Inhibition of neuronal ChE activities is the primary target of organophosphate poisoning.…”

“…4,5,22,40 The in vitro plasma or erythrocytes-organophosphate incubation test is a versatile and robust procedure acts as a predictor of potential toxicity of organophosphate insecticides. [24][25][26][27][28] This was accomplished in the present study (Table 2). These findings of in vitro blood ChE inhibition by dichlorvos strongly suggest the increased susceptibility of the diabetic patients to organophosphate poisoning.…”

“…The method of incubation of organophosphate with plasma or erythrocyte aliquots was used to measure the in vitro inhibition of plasma and erythrocyte ChE activities by the organophosphate insecticide dichlorvos (Sigma Aldrich, Germany) as described earlier. [25][26][27] Briefly, the aqueous dilution of the insecticide was added to the enzymatic reaction mixtures of the plasma or erythrocytes to obtain final concentrations in the reaction mixtures at 0 (base-line control), 0.5 and 1 µM. The reaction mixtures containing the insecticides were incubated at 37°C for 10 minutes to induce enzyme inhibition.…”

“…5,22,23 One important tool to assess the potential risk of organophosphates in man and animals is monitoring blood ChE inhibition in vitro. [24][25][26][27][28] We anticipate that changes in blood ChE activities in diabetic patients [7][8][9] might alter the in vitro susceptibility of blood ChE to organophosphate insecticides. The purpose of the present study was to examine in type-2 diabetic patients vs. healthy controls the plasma and erythrocyte ChE inhibition in vitro by the organophosphate dichlorvos which is used as an insecticide in agriculture and in veterinary practice.…”