A Method for the Detection of Atypical Forms of Human Serum Cholinesterase. Determination of Dibucaine Numbers

Abstract

Cases with atypical esterase activity were found by determining esterase inhibition in numerous sera. A suitable inhibitor was the local anaesthetic dibucaine (cinchocaine, T N Nupercainc, Perkain). A good discrimination between typical and atypical sera was obtained under the following conditions: 'I'he esterase activity of human serum diluted 1:100 was measured with a recording spectrophotometer a t 240 mp. l'he substrate was 5 X M benzoylcholine dissolved in M / 1 5 phosphate buffer, pH 7 . 4 . The concentration of the inhibitor was M . With tlie experimeiltal temperature around 25" C., the alTerage inhibition of the typical enzyme was 78.8 + 0.3%. The inhibition of the atypical esterases was less; in rare cases the inhibition was only 16'56. For each person, the inhibition characteristics were constant over a period of se\.eral months, and independent of the esterase level. l'he degree of inhibition mrasured under these conditions and expressed in per cent has been termed "Dibucaine Number". 'ManuscriptCan. J. Biochem. Physiol. Downloaded from www.nrcresearchpress.com by San Francisco (UCSF) on 12/09/14For personal use only.

Dibucaine Inhibition of Serum Cholinesterase

“…Dibucaine number determinations DN was determined as described by Kalow and Genest (1957). The assay mixture consisted of a 66.7 mM phosphate buffer (pH 7.4), 50 µM benzoylcholine, and 20 µl plasma.…”

“…It hydrolyses these compounds which are sometimes used in clinical anesthesia to facilitate intubation or other medical procedures (Goedde et at., 1968;Hersh et al, 1974;Cook et al, 1989;Ostergard et al, 1992;Fleming et al, 1996). However, some patients were suxamethonium-sensitive and quantitatively low in SChE activity, a geneticallydetermined property (Kalow and Genest, 1957;Thompson and Wittaker, 1966;Hobbiger and Peck, 1969;VibyMogensen, 1981;Cattozzo et al, 1993;Mitchell and HarropGriffiths, 1994;Sockalingam and Green, 1995). Thus, a pretest must be used to determine the SChE phenotype prior to suxamethonium or mivacurium infusion, otherwise, there is the risk of prolonged muscular relaxation and apnea.…”

How Personalized Medicine Became Genetic, and Racial: Werner Kalow and the Formations of Pharmacogenetics

“…This, in turn, depended on enzyme structure. 21 Offered a faculty position in the Department of Pharmacology at the University of Toronto in 1951, and eager to avoid being drafted a second time--this time into the United States Army for the Korean War --Kalow moved once more. He worked on a variety of projects at first.…”

Apnee a la succinyldicholine: etude d’une population canadienne-française

“…It is now well established that serum cholinesterases, also known as pseudocholinesterases, are responsible for the hydrolysis of succinyldicholine. In 1955, Kalow, et al 5,6 described the first technique that clarified the molecular structure of this specific enzyme. Studying the serum of patients who suffered from prolonged apnoea after administration of succiny]dicholine, they confirmed Lehrnann's findings 7,s by demonstrating a definite structural abnormality in their pseudocholinesterase molecule.…”