AUTOMATED PROCEDURE FOR ESTIMATION OF BLOOD CHOLINESTERASE ACTIVITIESIN RABBITS

An automated procedure for estimation of blood cholinesterase activiti es was evaluated and used to determine baseline cholinesterase activit ies in rabbits, In addition, the kinetics of cholinesterase inhibition and recovery from diazinon challenge were determined by use of this p rocedure, The procedure developed is a modification of the colorimetri c Ellman technique, adapted for use with the Instrumentation Laborator y Multistat III Plus Centrifugal Analyzer, The substrate used in this technique was acetylthiocholine, Baseline cholinesterase activities in domestic rabbits were plasma cholinesterase, 360 mU/ml; red blood cel l cholinesterase, 2,658 mU/ml; and whole blood cholinesterase, 1,332 m U/ml, Rabbits were challenged with 0.3 LD50 (40 mg/kg) of diazinon, an d blood samples were obtained at hourly, then daily intervals, Choline sterase activity in these samples was determined to monitor the effect of the cholinesterase inhibitor diazinon in vivo, as estimated by the Multistat III Plus Centrifugal Analyzer procedure, Plasma cholinester ase activity decreased to 4% within 6 h, whereas red blood cell cholin esterase activity decreased to 51%, By 10 days, plasma and red blood c ell cholinesterase activities had returned to 100 and 91%, respectivel y, of pre-challenge activities.