Reference values for erythrocyte acetylcholinesterase and plasma cholinesterase activities in children, implications for organophosphate intoxication

Abstract

Acetylcholinesterase and cholinesterase activity was measured in the blood of both healthy children 0-12 years of age and adults by a recently developed radiochemical method. Children less than 4 months of age were found to have lower levels for these enzymes than adults. Above this age, however, similar values were obtained for children and adults. A case report of an organophosphate intoxication is presented and is discussed in the light of our results.

Acetylcholinesterase in red blood cells

“…Adult levels are acquired between 1 month and 4 months of age, and there does not appear to be significant sex variation in red cell AChE activity [43]. Lund-Karlsen et a1 [37] confirmed that, up to 4 months of age, infants have lower levels of the enzyme, and they established reference values for children that might be useful in cases of organophosphate intoxication. It is difficult to understand why these differences in enzyme levels should exist, and the phenomenon of stress reticulocytosis has been put forward as a possible explanation.…”

“…This is supported by the fact that certain isolated abnormalities of AChE in human red cells are not associated with a change in erythrocyte lifespan. For instance, familial reduction of AChE is not associated with anemia or any signs and symptoms of ill health [36], and accidental poisoning with organophosphates has not been reported to be associated with anemia [37,38]. Furthermore, Metz et a1 [39], in elegant, controlled experiments in humans, showed that in vivo inhibition of red cell AChE with a "safe" (peripherally acting) inhibitor did not produce a shortened erythrocyte lifespan or anemia, and De Sandre et al [40] incubated erythrocytes with diisopropyl fluorophosphate (DFP) until their AChE activity had dropped to 5% of the original value.…”

Transient Plasma Cholinesterase Deficiency in Preterm Infants

“…This implies that new borns share a comparable risk to adults of succinylcholine-induced compli cations if ChE activity is significantly decreased. [5] studied ChE activity using an ultraviolet spectrophotometric method in 42 healthy term infants (from birth to 6 months) and found an average of 50% decrease in ChE levels in all the infants studied and suggested that the dose of succinylcholine be reduced by one third in infants less than 1 year of age. We were not able to demonstrate any significant difference of abnormally low ChE levels between adults and newborn infants using a different substrate to assay enzyme activity.…”

“…Cholinesterase, found in smooth muscle, liver, adipocytes and plasma, is a glycoprotein without a clear biological function. Clinical significance is attributed to succinylcholine sensitivity in the presence of decreased enzyme activity [2], Approxi mately 3% of the adult population has a genetic basis (heterozygotes) for decreased activity of this enzyme [3], Reported levels of ChE in healthy term newborns and in infants of up to 4 months of age range from 50 to 75% of normal adult values [4,5]. Levels in adults with ChE variants (atypical enzyme forms) range from 22 to 86% of normal values [1], Preterm infants are surviving at greater rates since the early 1970s, consequently, they are increasingly exposed to anesthetic and paralytic agents.…”

Use of biomarkers to indicate exposure of children to organophosphate pesticides: implications for a longitudinal study of children's environmental health.

“…Genetic influences not related to sex, race, or age account for 23% of variation in AChE activity levels among humans (Lessenger and Reese 1999). AChE levels in children younger than 4 months have been shown to be lower than for adults, whereas levels in children older than 4 months were comparable with those of adults (Karlsen et al 1981). Pregnancy, diseases, medications, and illegal drugs affect AChE levels in adults (De Peyster et al 1993;Lessenger and Reese 1999).…”