engleski

Cholinesterase activities in human whole blood measured with acetylthiocholine as substrate and ethopropazine as a selective inhibitor

Inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities in whole blood is an indicator of absorption of cholinesterase inhibitors, such as the highly toxic organophosphorus nerve agents. A standardized procedure for routine measurement of AChE and BChE activities in whole blood was discussed at the CMBTS-III meeting in Spiez in 2000. In that procedure, erythrocyte AChE activity is measured with acetylthiocholine (ATCh) as substrate in the presence of ethopropazine, which inhibits 97-98% the usual plasma BChE and 5-9% the AChE. Plasma BChE activity is measured with butyrylthiocholine (BTCh) as substrate, because BTCh is a very poor substrate for AChE. We suggest here a further simplification, which requires only one substrate (ATCh) and ethopropazine. The activity of both enzymes in whole blood is measured with 1.0 mM ATCh in the absence (vt) and in the presence (ve) of 20 mM ethopropazine ; ve corresponds to erythrocyte AChE. The difference Dv = vt - ve should correspond to plasma BChE (vp). This was tested on whole blood and plasma from ten individuals. All individuals belonged to the usual BChE phenotype ; all ve activities were corrected for inhibition caused by 20 mM ethopropazine. The calculated BChE activity (Dv) was on average 7% lower than the measured BChE activity (vp). We consider that this discrepancy is acceptable.

acetylcholinesterase; butyrylcholinesterase; assays in whole blood; inhibition by organophosphates

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