THE MEASUREMENT OF BETA-PHENYLETHYLAMINE IN HUMAN PLASMA AND RAT-BRAIN

A sensitive and specific analytical method has been developed for the measurement of beta-phenylethylamine (PEA) in human plasma and rat brain extracts. The method involves solvent extraction of PEA with cycle-hexane in the presence of amphetamine or phenylpropylamine (PPA) as internal standards. Automated precolumn derivatization with o-phthalaldehyde and 2-mercaptoethanol followed by reverse-phase HPLC separated PEA and PPA from endogenous interferences. Detection and quantification were carried out by amperometric detection at +0.75 V relative to a Ag/AgCl reference electrode or by coulometric detection with analytical cell potentials set at +0.29 and +0.50 V. The limit of detection for PEA was 10 pg and the limit of quantification in plasma was 60 pg/ml. The within-day and day-to-day coefficients of variation were 16.1% (n = 3) and 40.6% (n = 8), respectively, at a plasma concentration of 154 pg/ml and 15.2% (n = 5) and 28% (n = 10) at a brain extract concentration of 110 pg/ml. Basal endogenous plasma PEA concentrations of 335 +/- 255 pg/ml (n = 12, range 127-1002 pg/ml) were found for normal volunteers and single, daily doses of 24 mg but not 12 mg of the MAO-B inhibitor, mofegiline, were shown to increase plasma PEA significantly. Basal whole brain and striatal concentrations were 0.584 +/- 0.243 ng/g wet wt (n = 3) and 2.89 +/- 1.03 ng/g wet wt (n = 4), respectively. Statistically significant increases (5.7-fold) in rat whole brain PEA concentrations were seen 3 and 6 h following the administration of a single dose of 0.3 mg/kg mofegiline to rats. (C) 1994 Academic Press,Inc.