A quick and simple method for the routine determination of acetyl- and butyrylcholinesterase in blood.

The salient features of this method for biological monitoring of occupational exposure to organophosphorus insecticides are: (a) acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) are determined separately in whole haemolysed blood using specific substrates at appropriate concentrations; (b) 20 microliter of blood drawn from the finger tip is sufficient for both determinations; (c) the blood sample is immediately diluted with a solution of saponin and may thereafter be frozen for storage; (d) diagnostic kits, commercially available for the determination of plasma BuChE, may be employed with modifications; (e) the kinetic procedure is avoided by blocking the enzyme reactions at the end of the incubation period. This paper describes attempts to achieve optimal conditions for the two reactions. Under the conditions finally chosen, the whole blood 'AChE' activity value still includes a small percentage of plasma BuChE activity (12.5% of the total), while the whole blood 'BuChE' activity includes a small percentage of erythrocyte AChE activity (7% of the total). Results of determinations performed with this procedure on 172 healthy subjects are reported.