Red Blood Cell and Total Blood Acetylcholinesterase and Plasma Pseudocholinesterase In Humans: Observed Variances

Although acetylcholinesterase is the target molecule of organophosphate poisoning, it is not always assayed in clinical evaluations which include only the determination of plasma or serum cholinesterase. In this paper we present observations on workers exposed to, or poisoned by, ethylparathion. Acetylcholinesterase decreased earlier and more intensely than cholinesterase, with the suggestion of an initial increase of acetylcholinesterase activity in newly exposed, workers. A simplified standard Ellman assay of total acetylcholinesterase activity of hemolyzed total blood correlated with that of washed erythrocyte acetylcholinesterase. All results were standardized to both red blood cell and hemoglobin concentration. Normal values in a group of unexposed subjects were acetylcholinesterase: 1225 +/- 181 nU x 10/RBC and 39.30 +/- 5.05 U/g Hb for men, 1321 +/- 234 nU x 10/RBC and 42.57 +/- 6.85 U/g Hb for women. Differences between total and erythrocyte acetylcholinesterase were not statistically significant. Plasma cholinesterase appeared to be decreased in pregnancy and increased in anesthesia, liver and kidney disease and neuropathologic conditions attributed to metal poisoning while total acetylcholinesterase was unaffected. The determination of both cholinesterase and acetylcholinesterase assists the evaluation of individuals exposed to or poisoned by organophosphate, the differentiation of other conditions affecting cholinesterase and the recognition of genetically atypical cholinesterase.