title: Substrate stereoselectivity and enantiomer/enantiomer interaction in propranolol metabolism in rat liver microsomes.
abstract: The substrate stereoselectivity and enantiomer/enantiomer interaction of (S)- and (R)- propranolol for the formation of their metabolites were investigated in rat liver microsomal fractions. The enantiomers of primary metabolites of propranolol, 4-, 5-, 7-hydroxy- and N-desisopropyl-propranolol were separated and assayed by an HPLC method employing a chiral ovomucoid column. Regioselective substrate stereoselectivity (R < S for 4- and 5-hydroxylations; R > S for 7-hydroxylation; R = S for N-desisopropylation) was observed in the formation of propranolol metabolites when the individual enantiomers or a racemic mixture of propranolol were used as substrates. Concentration-dependent metabolic inhibition of propranolol enantiomers by their optical isomers was also observed. In addition, the inhibition of propranolol 4-, 5- and 7-hydroxylations between the enantiomers showed a typical competitive nature. These findings suggested that the propranolol enantiomers competed for the same enzyme, probably a cytochrome P450 isozyme in the CYP2D subfamily.
authors.affiliation: Laboratory of Biopharmaceutics, Faculty of Pharmaceutical Sciences, Chiba University, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Masubuchi
authors.forename: L A
authors.initials: LA
authors.lastname: Yamamoto
authors.forename: M
authors.initials: M
authors.lastname: Uesaka
authors.forename: S
authors.initials: S
authors.lastname: Fujita
authors.forename: S
authors.initials: S
authors.lastname: Narimatsu
authors.forename: T
authors.initials: T
authors.lastname: Suzuki
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D006900:Hydroxylation; D007700:Kinetics; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D011433:Propranolol / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000493:pharmacokinetics; D051381:Rats; D017208:Rats, Wistar; D013237:Stereoisomerism
chemical_list: D011433:Propranolol