ObjectiveAcceleratory and inhibitory receptors have been described on the pseudocholinesterase (PCHE) molecule. An increased PCHE activity has been reported in patients with chronic pain and anxiety, conditions known to be correlated with increased plasma catecholamine levels. Aim of this laboratory investigation was to determine whether catecholamines have an effect on PCHE activity, as this knowledge could help to define the role of PCHE in the assessment of stress.MethodsAfter Ethics committee approval and written informed consent, 3 ml of blood was collected from five healthy volunteers. Fourteen samples of 50 μl each were prepared from each of the volunteer’s plasma. Epinephrine (25, 50, 100, 200, 400 and 1000 pg) and norepinephrine (50, 100, 200, 400, 800 and 2000 pg) were added to samples of each subject. Sodium-chloride solution was added to control samples. PCHE activity was photometrically assessed.ResultsPCHE activity was significantly higher after the addition of epinephrine (median 8304 versus 7386 U/l). This effect was not dose-dependent. PCHE activity did not change after addition of norepinephine.ConclusionsThis mechanism might explain previous findings that showed higher levels of PCHE activity in the presence of chronic pain and anxiety. In the absence of a dose–response curve in the concentration range studied, PCHE activity does not appear to be suitable for the assessment of levels of stress.