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A conversion factor between two cholinesterase assays and its application in establishing a normal range for human RBC AChE.
Arrieta DE; Nihart VM; Henderson JD; McCurdy S; Lefkowitz LJ; Wilson BW
Toxicologist 2005 Mar; 84(Suppl 1):262
The Cholinesterase (ChE) Reference Laboratory (CRL) at the US Army Center for Health Promotion and Preventive Medicine (USACHPPM) uses a modification of the delta pH method of Michel to annually analyze over 15,000 blood specimens from personnel that predominantly work at chemical agent storage sites and chemical demilitarization facilities. UC Davis and CRL are collaborating to derive a conversion factor between the delta pH and the colorimetric Ellman ChE assays. The factor is used to estimate a normal range of Ellman determined human blood acetylcholinesterase (AChE) levels based on CHPPM's data. Human red blood cells (RBCs) from three volunteers were assayed at UCD by the delta pH and Ellman methods according to standard procedures. Both assays were carried out at 25 C, and with optimal final substrate concentrations: 10 mM acetylcholine bromide for the delta pH assay and 1 mM acetylthiocholine iodide for the Ellman assay. RBCs were treated with diisopropyl fluorophosphate to generate a dose/response curve of inhibition. This yielded an approximate conversion factor: delta pH = 0.091 Ellman + 0.052 with an r2 of 0.96. This approach permits converting the extensive CRL database of baseline (presumably unexposed) delta pH AChE values into a normal range of Ellman AChE activities, assays used to evaluate occupational exposure to pesticides. The estimated normal 95% range of human AChE for the Ellman assay was 7.12 to 9.10 umol/min/mL with a mean value of 8.23 +/- 0.62 SD umol/min/mL.
Blood-analysis; Chemical-analysis; Chemical-factory-workers; Chemical-industry-workers; Chemical-manufacturing-industry; Red-blood-cells; Blood-cells; Chemical-warfare-agents
The Toxicologist. Society of Toxicology 44th Annual Meeting and ToxExpo, March 6-10, 2005, New Orleans, Louisiana
University of California - Davis
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Content source: National Institute for Occupational Safety and Health Education and Information Division