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Clinical Chemistry, Vol 16, 503-506, Copyright © 1970 by the American Association for Clinical Chemistry
1 Atlanta Toxicology Laboratory Branch, Division of
Pesticide Chemistry and Toxicology, Food and Drug Administration, Department of Health, Education and Welfare, Atlanta,
Ga. 30333.
Plasma pseudocholinesterase has no known physiological role but is essential for the rapid degradation of succinylcholine, a muscle relaxant used in surgical procedures. Depression of effective enzyme concentrations as a result of hepatocellular disease or exposure to anticholinesterase agents will increase the patients sensitivity to succinylcholine and prolong postoperative apnea. Synthesis of this enzyme is controlled by an autosomal gene with multiple variant alleles; individuals phenotypically homozygotic for one of these variants will have either qualitatively "atypical" pseudocholinesterase with decreased activity or no enzyme at all, and will thus be more sensitive to succinylcholine. The automated pH stat system described here detects atypical cholinesterase by measuring the degree of inhibition of butyrylcholine hydrolysis by dibucaine. The sensitivity and reproducibility of this technique equals that of standard spectrophotometric methods and its speed is comparable to that of the most rapid screening tests. A family pedigree is also presented, exemplifying a rare genotype in which two siblings are double heterozygotes for "atypical" and "silent" alleles.
Submitted on February 25, 1970
Accepted on April 8, 1970
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