A SPECIFIC RADIOISOTOPIC ASSAY FOR ACETYLCHOLINESTERASE AND PSEUDOCHOLINESTERASE IN BRAIN AND PLASMA.
Technical rept. Jul 67-Sep 68,
EDGEWOOD ARSENAL MD
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The report presents a radiometric procedure for assaying acetylcholinesterase and pseudocholinesterase. The method is based on the adsorption of unreacted substrates as their acid-1-14C-choline esters on Amberlite CG-120 resin suspended in dioxane. The supernatant solution containing the product of enzyme hydrolysis, free acid-1-14C, is counted in a liquid scintillation spectrometer. Blank values are less than 0.5 of the total radioactivity of the substrate added initially. Assays can be made with less than 1 mg of brain tissue or 0.01 ml of plasma. The method is simple, rapid, and precise. Furthermore, it does not employ artificial substrates. Acetylcholinesterase and pseudocholinesterase can be distinguished by the use of selective inhibitors. Rates of hydrolysis are presented for the substrates Mecholyl, acetylcholine, and butyrylcholine with brain and plasma. A comparison of cholinesterase levels in several species has shown considerable species and individual variation. Author