Biphasic kinetics of imipramine N-oxidation in rat brain microsomes

Shizuo Narimatsu, Shigeo Yamamoto, Tomomi Koitabashi, Rika Kato, Yasuhiro Masubuchi, Tokuji Suzuki, Toshiharu Horie

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Imipramine (IMI) N-oxidase activity in brain microsomes from rats of both sexes was determined by high performance liquid chromatography, and compared with the results in rat liver microsomes. Brain and liver microsomal IMI N-oxidation was sensitive to thermal inactivation and had an optimal pH at around 9.0. IMI N-oxidase activity (15.54 pmol/min/mg protein) in brain microsomes was about one-hundredth that of liver microsomes (2.08 nmol/min/mg protein) at a substrate concentration of 5 mM. IMI N-oxidase activities in both brain and liver microsomes displayed biphasic kinetics that associated a low K(m)-low V(max) element with a high K(m)-high V(max) component. Furthermore, a significant sex difference was observed in V(max) values (male>female) in both phases, but K(m) values were similar between male and female rats, resulting in a significant sex difference (male>female) in intrinsic clearance values (V(max)/K(m)) of the low-K(m) and the high-K(m) phases.

Original languageEnglish
Pages (from-to)253-256
Number of pages4
JournalBiological and Pharmaceutical Bulletin
Volume22
Issue number3
Publication statusPublished - Mar 1999

Fingerprint

Imipramine
Microsomes
Liver Microsomes
Oxidoreductases
Brain
Sex Characteristics
Proteins
Hot Temperature
High Pressure Liquid Chromatography
Liver

Keywords

  • Biphasic kinetics
  • Flavin-containing monooxygenase
  • Imipramine N-oxide
  • Rat brain microsomes
  • Rat liver microsomes
  • Sex difference

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology, Toxicology and Pharmaceutics(all)

Cite this

Narimatsu, S., Yamamoto, S., Koitabashi, T., Kato, R., Masubuchi, Y., Suzuki, T., & Horie, T. (1999). Biphasic kinetics of imipramine N-oxidation in rat brain microsomes. Biological and Pharmaceutical Bulletin, 22(3), 253-256.

Biphasic kinetics of imipramine N-oxidation in rat brain microsomes. / Narimatsu, Shizuo; Yamamoto, Shigeo; Koitabashi, Tomomi; Kato, Rika; Masubuchi, Yasuhiro; Suzuki, Tokuji; Horie, Toshiharu.

In: Biological and Pharmaceutical Bulletin, Vol. 22, No. 3, 03.1999, p. 253-256.

Research output: Contribution to journalArticle

Narimatsu, S, Yamamoto, S, Koitabashi, T, Kato, R, Masubuchi, Y, Suzuki, T & Horie, T 1999, 'Biphasic kinetics of imipramine N-oxidation in rat brain microsomes', Biological and Pharmaceutical Bulletin, vol. 22, no. 3, pp. 253-256.
Narimatsu S, Yamamoto S, Koitabashi T, Kato R, Masubuchi Y, Suzuki T et al. Biphasic kinetics of imipramine N-oxidation in rat brain microsomes. Biological and Pharmaceutical Bulletin. 1999 Mar;22(3):253-256.
Narimatsu, Shizuo ; Yamamoto, Shigeo ; Koitabashi, Tomomi ; Kato, Rika ; Masubuchi, Yasuhiro ; Suzuki, Tokuji ; Horie, Toshiharu. / Biphasic kinetics of imipramine N-oxidation in rat brain microsomes. In: Biological and Pharmaceutical Bulletin. 1999 ; Vol. 22, No. 3. pp. 253-256.
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