The stereoselective metabolism of ethylamphetamine with fortified rabbit liver homogenates.

1. The liver enzyme systems of rabbits involved in the oxidative metabolism of ethylamphetamine were shown to be localized in the microsomal fraction. 2. The effect of substrate concentration, incubation period and storage of the microsomal preparations at 4 degrees was investigated. 3. The results indicate the involvement of at least two stereoselective enzyme systems or different conformations of binding of different substrates to the same enzyme system. R-(-)-Ethylamphetamine is the preferred substrate for N-oxidation and dealkylation, whereas the S-(+)-isomer is preferred for deamination. When racemic ethyl amphetamine is metabolized, the enantiomers act as independent compounds and compete for the enzymes. 4. Neither alpha-C- nor N-oxidation is induced by pre-treatment with phenobarbitone or 3-methylcholanthrene.