Comparison of different diluents and chromophores for spectrophotometric determination of livestock blood cholinesterase activity.

This research article describes an investigation into the impact of different diluents and chromophores on the spectrophotometric measurement of cholinesterase activity in the blood of various livestock species. The study found that distilled water and the chromophore 2- PDS yielded the best results for such measurements.

Research Purpose and Experiment Setup

• The objective of this research was to study and compare the effects of seven different blood diluents (distilled water, Triton X-100, saponin, isotonic saline solution, pH 7.5 and 8 phosphate buffers, and bovine serum albumin) and two chromophores (5, 5′-dithiobis 2-nitrobenzoic acid or DTNB and 2,2′-dithiodipyridine or 2- PDS) on the determination of cholinesterase (ChE) activity in the blood of four domestic species: cows, sheep, goats, and horses.
• These factors were explored with regard to their effect on the precision of ChE measurements, as well as their overall suitability for use in such tests.

Key Findings in the Study

• The study found that haemolytic diluents (which cause lysis, or breaking open of red blood cells), such as distilled water, Triton X-100, and saponin, gave the best precision results when fresh blood was tested.
• However, it was noted that Triton X-100 led to lower ChE activity values in horses, while saponin produced very high backgrounds in all species tested. Given these considerations, distilled water was recommended as the diluent of choice for determination of fresh blood cholinesterase.
• When frozen samples were used, all diluents except Triton X-100 yielded consistent final ChE results and showed good between-run precision.
• In terms of chromophores, the use of 2- PDS allowed for kinetic measurements with approximately one-third less haemoglobin interference than when DTNB was used. This advantage allows for the use of more concentrated whole blood samples, which improves the accuracy of measurements and reduces the potential reactivation of inhibited ChE.

Conclusion and Recommendations

• Based on the findings, the researchers recommend the use of distilled water as a diluent and 2- PDS as a chromophore for determining ChE activity in whole blood.
• These recommendations are useful for veterinary pathologists and chemists who work with spectrophotometric determinations of livestock blood cholinesterase, as they can aid in producing more accurate and consistent results.