Regioselective contribution of the cytochrome P-450 2D subfamily to propranolol metabolism in rat liver microsomes

Y. Masubuchi, N. Kagimoto, S. Narimatsu, S. Fujita, T. Suzuki

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31 Citations (Scopus)


The metabolism of propranolol was examined by using microsomes from Dark Agouti rats known as a poor-metabolizer animal model for debrisoquine 4- hydroxylation and Wistar rats. Propranolol 4- and 5-hydroxylations followed biphasic Michaelis-Menten kinetics, and 7-hydroxylation and N- desisopropylation were monophasic in both strains. The kinetic studies showed that the V(max) for propranolol 7-hydroxylase activity and the V(max) of high-affinity phases for propranolol 4- and 5-hydroxylase activities were markedly low in Dark Agouti rats compared with those in Wistar rats. The antibody against a cytochrome P-450 isozyme, P-450BTL (Suzuki, T., et al., Drug Metab. Dispos. 20, 367-373, 1992), belonging to the CYP2D subfamily, inhibited by 90% propranolol 4-, 5-, and 7-hydroxylase activities in liver microsomes from male Wistar rats at a low propranolol concentration (5 μM). However, less inhibitory effects of the antibody on propranolol 4- and 5- hydroxylase activities were observed at a high propranolol concentration (1 mM), whereas a similar inhibitory effect of the antibody on propranolol 7- hydroxylase activity was shown. The antibody inhibited propranolol N- desisopropylase activity, but less extent of the inhibition on this activity than those on ring-hydroxylase activities was observed at the low and high propranolol concentrations. These results indicate that a polymorphic cytochrome P-450 isozyme(s) belonging to the CYP2D subfamily is involved predominantly in propranolol 4-, 5-, and 7-hydroxylations at low substrate concentrations in the rat.

Original languageEnglish
Pages (from-to)1012-1016
Number of pages5
JournalDrug Metabolism and Disposition
Issue number6
Publication statusPublished - Jan 1 1993

ASJC Scopus subject areas

  • Pharmacology
  • Pharmaceutical Science


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