A reliable way of estimating cholinesterases from whole blood in the presence of anti-cholinesterases.

A method for the determination of cholinesterases [1] has been adapted to monitor these enzymes in the presence of anti-cholinesterase insecticides. The cholinesterases in blood samples, which were dried on filter papers, could be eluted with water (plasma cholinesterase) and with 1% Triton X-100 (erythrocyte acetylcholinesterase) with complete recovery of the enzyme activity. The samples could be stored at room temperature for at least two weeks and in a refrigerator more than six weeks without a decreased efficiency of elution from the filter paper. It was found that if blood samples to which the two insecticides, used to test the validity of the method, had been added, were stored on filter paper at room temperature or deep frozen for at least one week, there was the same inhibition of the cholinesterases as at the start of the experiment. The samples stored at room temperature in tubes, recovered maximally within a day. This modified method of cholinesterase determination will be especially suitable when samples have to be mailed to laboratories making the analysis.