Cholinesterase in porcine saliva: Analytical characterization and behavior after experimental stress

- A spectrophotometric method for cholinesterase measurement in porcine saliva was developed and validated.
- Salivary cholinesterase was characterized in porcine saliva and tested as stress biomarker.
- Butyrylcholinesterase was the main isoenzyme existing in porcine saliva.
- Salivary cholinesterase significantly increased after restraint with a nasal snare and a short-term road transport.
- Salivary cholinesterase could be a suitable stress biomarker in pigs.

The purpose of this study was to measure and characterize the enzyme cholinesterase (ChE) in porcine saliva, as well as to evaluate its behavior in experimental stressful conditions. The results of ChE characterization by using different substrates and the selective inhibitors ethopropazine and physostigmine showed that the main enzyme existing in porcine saliva was butyrylcholinesterase (BChE). An automated assay using butyrylthiocholine iodide as substrate was validated providing adequate reproducibility, linearity results and limit of detection. Salivary ChE was measured using the validated assay in two models of acute stress: twenty pigs stressed for 2 min with a nasal snare and other twenty pigs subjected to a short-term road transport. Salivary ChE significantly increased after restraint and transport stress in pigs, as well as the ChE to total protein ratio. In conclusion, BChE is the predominant isoenzyme in porcine saliva, it can be measured by the fast, simple and automated method described in this paper and it increases in the models of stress used in this study.