Rapid Estimation of Serum Cholinesterase Activity Using the Astrup Micro Equipment.

A rapid micro technique for the estimation of serum cholinesterase is described. Acetylcholine bromide is incubated with serum within the capillary of the Astrup electrode. The enzyme hydrolyses the substrate with the liberation of acetic acid. This causes a fall of pH which is seen on the galvanometer of the instrument and the rate of this fall is shown to be proportional to enzyme concentration. The method has been calibrated in international units and compared with a more conventional technique. The values found in homozygotes with normal dibucaine-resistant enzymes and in heterozygotes are reported, together with their dibucaine and fluoride numbers.