Adaptation of a dynamic in vitro model with real-time determination of butyrylcholinesterase activity in the presence of cyclosarin and an oxime

- We adopted an in vitro model for the continuous real-time determination of human BChE activity.
- The interactions of human BChE, cyclosarin and the oxime HLö 7 were investigated.
- This model allows the investigation of BChE as a 'pseudo-catalytic' scavenger.

The well-established dynamic in vitro model for the real-time determination of acetylcholinesterase activity was modified for use of human butyrylcholinesterase (BChE) activity. Human plasma as BChE source was layered on a syringe filter and the enzyme reactor was continuously perfused with phosphate buffer, butyrylthiocholine and Ellman's reagent at pH 7.4 and 37 °C which resulted in a stable BChE activity for up to 240 min. Then, the model was applied for investigating the suitability of human BChE in combination with an oxime (HLö 7) to serve as a 'pseudo-catalytic' scavenger of the organophosphorus nerve agent cyclosarin. The application of different perfusion protocols demonstrated the ability of BChE-oxime combinations to prevent BChE from irreversible inhibition by cyclosarin even at toxicologically relevant concentrations. In the end, this model seems to be suitable for the investigation of human plasma BChE as an endogenous, 'pseudo-catalytic' scavenger of a variety of nerve agents.