Introduction: Plasmacholinesterase activity levels of various species may be of interest to toxicologists or pathologists
working with chemicals that interfere with the activity of plasma cholinesterase. Methods: We used a
pH titration method to measure the plasma cholinesterase activity of six mammalian species. Results: Plasma
cholinesterase activity varied up to 50-fold between species: sheep (88 ± 45 nM acetylcholine degraded per
ml of test plasma per minute), cattle (94 ± 35), western grey kangaroos (126 ± 92), alpaca (364 ± 70), rats
(390 ± 118) and horses (4539 ± 721). Discussion: We present a simple, effective technique for the assay of
plasma cholinesterase activity levels from a range of species. Although labour-intensive, it requires only basic
laboratory equipment.