Yuknavage K L, Fenske R A, Kalman D A, Keifer M C, Furlong C E
Department of Environmental Health, University of Washington, Seattle, USA.
J Toxicol Environ Health. 1997 May;51(1):35-55. doi: 10.1080/00984109708984010.
The extensive international use of organophosphorus compounds (OP) results in numerous acute intoxications each year. OPs inhibit acetylcholinesterase, the enzyme responsible for breaking down the neurotransmitter acetylcholine. The World Health Organization recognizes cholinesterase (ChE) biomonitoring as a preventive measure against OP overexposure. The aim of this study was to determine if dermal OP contamination could interfere with current field ChE biomonitoring assays, which use a fingerstick blood sample. In this study we also sought to determine if high levels of a plasma enzyme, A-esterase, could protect ChE from inhibition by hydrolyzing environmentally generated oxons potentially present in a fingerstick sample. A heparinized venous blood sample was collected from a volunteer. Erythrocyte acetylcholinesterase (AChE) and plasma butyrylcholinesterase (PChE) activities were measured using a field-based colorimetric cholinesterase kit. ChE dose-response curves were constructed by allowing 10-microliters blood samples to contact environmentally realistic levels of OP thioate and oxon for 10 s. An inhibition threshold could not be established for PChE when exposed to oxon within the time necessary to perform a fingerstick analysis. AChE was also inhibited by trace amounts of oxon consistent with previously reported environmental levels. These findings suggest that the reliability of field-based biomonitoring results is limited if OP residues remain on a skin surface at the time of sample collection. A-esterase's role in protecting ChE activity was investigated using capillary and venous blood from 30 unexposed individuals. Baseline ChE activities were measured, as were individual A-esterase activities using paraoxon, diazoxon, and phenylacetate as substrates. Results were then compared to ChE activities measured after 10 s of contact with an environmentally realistic amount of OP, containing 1% oxon. Both ChE activities were significantly inhibited, with capillary values being significantly more inhibited than their venous counterparts. However, no protective effect could be associated between the degree of A-esterase activity and the subsequent level of ChE inhibition observed in an individual's blood. These results suggest that (1) if there is any uncertainty about OP skin contamination, venous blood would be a more appropriate specimen to employ when using field ChE biomonitoring kits--it is collected in larger volumes and has essentially no direct contact to dermal surfaces; and (2) A-esterase activity demonstrates no protective effect against ChE inhibition upon a blood droplet's brief contact with an OP residue containing traces of oxon.
有机磷化合物（OP）在国际上的广泛使用导致每年发生大量急性中毒事件。OP会抑制乙酰胆碱酯酶，该酶负责分解神经递质乙酰胆碱。世界卫生组织认可胆碱酯酶（ChE）生物监测作为预防OP过度暴露的一项措施。本研究的目的是确定皮肤OP污染是否会干扰当前使用指尖血样本的现场ChE生物监测检测方法。在本研究中，我们还试图确定血浆中的一种酶——A酯酶的高水平是否能够通过水解指尖血样本中可能存在的环境生成的氧磷化物来保护ChE不被抑制。从一名志愿者身上采集了一份肝素化静脉血样本。使用基于现场的比色胆碱酯酶试剂盒测量红细胞乙酰胆碱酯酶（AChE）和血浆丁酰胆碱酯酶（PChE）的活性。通过让10微升血液样本与环境实际水平的OP硫代酸酯和氧磷化物接触10秒来构建ChE剂量反应曲线。当在进行指尖血分析所需的时间内暴露于氧磷化物时，无法确定PChE的抑制阈值。AChE也受到痕量氧磷化物的抑制，这与先前报道的环境水平一致。这些发现表明，如果在样本采集时OP残留物仍留在皮肤表面，那么基于现场的生物监测结果的可靠性是有限的。使用30名未接触者的毛细血管血和静脉血研究了A酯酶在保护ChE活性方面的作用。测量了基线ChE活性，以及使用对氧磷、重氮氧磷和苯乙酸作为底物的个体A酯酶活性。然后将结果与在与环境实际量的OP（含1%氧磷化物）接触10秒后测量的ChE活性进行比较。两种ChE活性均受到显著抑制，毛细血管血的值比静脉血的值受到的抑制更显著。然而，在个体血液中观察到的A酯酶活性程度与随后的ChE抑制水平之间未发现保护作用。这些结果表明：（1）如果对OP皮肤污染存在任何不确定性，那么在使用现场ChE生物监测试剂盒时，静脉血将是更合适的样本——它采集量更大且基本上不与皮肤表面直接接触；（2）在血滴与含有痕量氧磷化物的OP残留物短暂接触时，A酯酶活性对ChE抑制没有保护作用。
