Mohammad F K, Alias A S, Ahmed O A H
College of Veterinary Medicine, University of Mosul, Mosul, Iraq.
J Med Toxicol. 2007 Mar;3(1):25-30. doi: 10.1007/BF03161035.
The measurement of blood cholinesterase activity is a useful tool for monitoring exposure to organophosphate and carbamate insecticides. Blood cholinesterase activity is measured colorimetrically or electrometrically. Recently, a simple and practical electrometric method has been described and validated for measuring blood cholinesterase activity in people and animals. The purpose of the present report was to use the modified electrometric technique for measuring blood (plasma, erythrocyte and whole blood) cholinesterase activities in apparently healthy human volunteers in Mosul, Iraq.
Cholinesterase activities in the plasma, erythrocytes, and whole blood of healthy male (n = 72) and female (n = 31) volunteers were measured by an electrometric method; the method involved the addition of 0.2 ml of blood sample to 3 ml of distilled water followed by 3 ml of barbital-phosphate buffer solution (pH 8.1). The pH (pH1) of the mixture was measured, and then 0.1 ml of 7.5% of acetylcholine iodide, as a substrate, was added. The reaction mixture was incubated at 37 degrees C for 20 minutes. The pH (pH2) of the reaction mixture was measured after the end of the incubation period. Enzyme activity was expressed as DeltapH/20 min = pH1- pH2 - (DeltapH of the blank). The blank was without the blood sample. Following in vitro inhibition of pseudo cholinesterase by quinidine sulfate, true cholinesterase activity was estimated in the plasma of the subjects. After in vitro addition of the organophosphate (chlorpyrifos and methidathion, 0.5 and 1 microM) and carbamate (carbaryl, 5 and 10 microM) insecticides to the reaction mixtures, inhibitions of blood cholinesterases were measured.
Mean reference cholinesterase activities (DeltapH/20 min) in the plasma, erythrocytes, and whole blood of male subjects were 0.98, 1.39, and 1.41, respectively. Females were 0.85, 1.22, and 1.23, respectively. Ten minutes after in vitro addition of quinidine sulfate to inhibit pseudo cholinesterase activity in the plasma, the estimated true cholinesterase activities in males and females were 0.08 and 0.07 DeltapH/20 min, respectively. The percentage of true cholinesterase in the plasma of males and females was 8.2. Using the modified electrometric method, various percentages of cholinesterase inhibitions in the plasma, erythrocytes, and whole blood were detected after in vitro addition of the organophosphate insecticides (chlorpyrifos and methidathion) and the carbamate insecticide (carbaryl) to the reaction mixtures.
These findings are the first collective report of human plasma, erythrocyte, and whole blood cholinesterase activities as determined by the modified electrometric method, and they could serve as reference points for future studies that involve human exposure to anticholinesterase pesticides.
血液胆碱酯酶活性的测定是监测有机磷和氨基甲酸酯类杀虫剂暴露情况的有用工具。血液胆碱酯酶活性通过比色法或电位法进行测定。最近，一种简单实用的电位法已被描述并验证可用于测量人和动物的血液胆碱酯酶活性。本报告的目的是使用改良的电位技术来测量伊拉克摩苏尔表面健康的人类志愿者血液（血浆、红细胞和全血）中的胆碱酯酶活性。
通过电位法测量健康男性（n = 72）和女性（n = 31）志愿者血浆、红细胞和全血中的胆碱酯酶活性；该方法包括将0.2 ml血液样本加入3 ml蒸馏水中，然后加入3 ml巴比妥 - 磷酸盐缓冲溶液（pH 8.1）。测量混合物的pH（pH1），然后加入0.1 ml 7.5%的碘化乙酰胆碱作为底物。反应混合物在37℃孵育20分钟。孵育期结束后测量反应混合物的pH（pH2）。酶活性表示为ΔpH/20分钟 = pH1 - pH2 - （空白的ΔpH）。空白不含血液样本。在硫酸奎尼丁对假性胆碱酯酶进行体外抑制后，估计受试者血浆中的真性胆碱酯酶活性。在反应混合物中体外加入有机磷（毒死蜱和杀扑磷，0.5和1 microM）和氨基甲酸酯（西维因，5和10 microM）杀虫剂后，测量血液胆碱酯酶的抑制情况。
男性受试者血浆、红细胞和全血中的平均参考胆碱酯酶活性（ΔpH/20分钟）分别为0.98、1.39和1.41。女性分别为0.85、1.22和1.23。在体外加入硫酸奎尼丁抑制血浆中的假性胆碱酯酶活性10分钟后，男性和女性的估计真性胆碱酯酶活性分别为0.08和0.07 ΔpH/20分钟。男性和女性血浆中真性胆碱酯酶的百分比为8.2。使用改良的电位法，在反应混合物中体外加入有机磷杀虫剂（毒死蜱和杀扑磷）和氨基甲酸酯杀虫剂（西维因）后，检测到血浆、红细胞和全血中不同百分比的胆碱酯酶抑制情况。
这些发现是通过改良电位法测定人血浆、红细胞和全血胆碱酯酶活性的首份综合报告，可为未来涉及人类接触抗胆碱酯酶农药的研究提供参考依据。
