IDENTIFICATION OF HUMAN PLASMA CHOLINESTERASE VARIANTS IN 6,688 INDIVIDUALS USING BIOCHEMICAL-ANALYSIS

In 1973, a Cholinesterase Research Unit was established in Denmark (DC RU). The primary aim was to provide a central service for determining genotypes and activity of plasma cholinesterase (BChE) in patients sho wing abnormal response after succinylcholine. The purpose of the prese nt study was, on the basis of 20 years experience with this Unit, to e stablish accurate reference intervals for BChE activity and inhibition values for the different genotypes of BChE. Also we wanted to evaluat e the influence of age and sex on the BChE activity in genotypically n ormal patients. Plasma cholinesterase activity was measured using benz oylcholine as substrate. The genetic variations of the enzyme were ide ntified using differential inhibitors, i.e: Dibucaine, Sodium Fluoride , Succinylcholine, Urea and Re-2-0683. We investigated 6,688 patients. The reference values for the 13 genotypes represented agree with prev ious findings. In genotypically normal patients, no age or sex differe nces were found in BChE activity in children below the age of 10 years . From the age of 10 years the activity decreased significantly in bot h males and Females, the activity in females being significantly lower than in males. In females the activity was lowest in the age group 30 -40 years, returning to prepuberty level at about 60 years of age. In males the activity decreased slightly up to 50-60 pears of age. Hereaf ter the activity was stable or tended to increase slightly. Most genot ypes could be recognized using the results of the different inhibition studies. We found the inhibitors Dibucaine, Sodium fluoride, Urea and Ro-2-0683 most helpful, whereas succinylcholine was of less value. We conclude that though most genotypes can be recognized biochemically s everal variants with heterozygous occurrence of an abnormal and a usua l gene are still very difficult or impossible to differentiate in this way. This, together with the increasing number of possible genotypes, have increased the need for rests based on DNA analyses.