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  • Title: Hydrogen peroxide (H2O2) production by monoamine oxidase in rat tissues using endogenous catecholamines as substrates. A comparison of catalytic monoamine oxidase histochemistry and recently published catechol-O-methyltransferase immunohistochemistry.
    Author: Nakos G, Gossrau R.
    Journal: Acta Histochem; 1995 Jan; 97(1):121-7. PubMed ID: 7771182.
    Abstract:
    Histochemical studies on hydrogen peroxide (H2O2) production by monoamine oxidase (MAOX) using xenobiotic (foreign) catecholamines such as tryptamine or tyramine as substrates may not reveal the true H2O2-production capacity of this enzyme and the potential co-localization and cooperation of MAOX with catechol-O-methyltransferase (COMT), the other catecholamine-degrading enzyme. Therefore, in the present study the catecholamine hormones adrenaline (epinephrine) and noradrenaline (norepinephrine) and the catecholamine neurotransmitter noradrenaline as well as the COMT metabolites metanephrine and normetanephrine, which are likely to be the more important MAOX substrates, were used for MAOX visualization in many rat tissues with a cerium-diaminobenzidine-H2O2-Co method. Adrenaline and noradrenaline were autooxidized by Ce3+ and could not be employed; with metanephrine or normetanephrine as substrates MAOX produced considerable amounts of H2O2 in many cells and tissues. Comparisons with immunohistochemical COMT-data for rats from the literature show that MAOX and COMT are co-localized or not. Therefore, different from our current knowledge in rats COMT and MAOX either co-operate in catecholamine degradation or they degrade the respective catecholamines alone.
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