Evidence for the Localization of Hydrogen Peroxide‐Stimulated Cyclooxygenase Activity in Rat Brain Mitochondria: A Possible Coupling with Monoamine Oxidase

András Seregi, Péter Serfózó, Zsuzsanna Mergl

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Abstract: The distribution of basal and of H2 O2‐ stimulated cyclooxygenase activity in the primary fractions of rat brain homogenates and in the subfractions of crude mitochondrial fraction was studied. For comparison, the localization of H2 O2‐ generating monoamine oxidase (MAO) as well as that of the mitochondrial marker succinate dehydrogenase (SDH) was also examined. H2 O2 was generated by MAO using 5 × 10−4M noradrenaline (NA) or 2 × 10−4M 2‐phenylethylamine (PEA) as substrates, or by 25 μg glucose oxidase (GOD) per ml in the presence of 1 mM glucose. For nonstimulated (basal) cyclooxygenase, the relative specific activity (RSA) was high in microsomes (1.79) and in the free mitochondria‐containing subfraction of the crude mitochondrial fraction (1.94). Parallel distribution of MAO and H2 O2‐ stimulated cyclooxygenase was observed in all fractions studied in the presence of NA. The highest RSA was found in the purified mitochondria for both enzymes (1.85 for MAO and 1.97 for H2 O2‐ stimulated cyclooxygenase). The enrichment of SDH (RSA = 2.21) indicated a high concentration of mitochondria in this fraction. The same distribution of H2 O2‐ stimulated cyclooxygenase was obtained when, instead of the MAO‐NA system, hydrogen peroxide was generated by GOD in the presence of glucose. H2 O2 generated by deamination of NA or PEA by MAO, or during the enzymatic oxydation of glucose by GOD, caused a threefold increase in mitochondrial endoperoxide formation. Indomethacin (2 × 104M), catalase (50 μg/ml) and pargyline (2 × 10−4M) eliminated the MAO‐dependent mitochondrial synthesis of PG endoperoxides. The GOD‐dependent cyclooxygenase activity of this fraction was abolished by in domethacin or catalase, but not by pargyline. The results show the existence of a mitochondrial cyclooxygenase in brain tissue. The enzyme is sensitive to H2 O2 and produces prostaglandin endoperoxides from an endogenous source of arachidonic acid. The identical localization of H2 O2‐ producing MAO and H2 O2‐ sensitive cyclooxygenase suggests a possible coupling between monoamine and arachidonic acid metabolism.

Original languageEnglish
Pages (from-to)407-413
Number of pages7
JournalJournal of neurochemistry
Issue number2
Publication statusPublished - Feb 1983


  • Cyclooxygenase
  • Hydrogen peroxide
  • Mitochondria‐Brain tissue
  • Monoamine oxidase

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

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