Journal
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
Volume 284, Issue 4, Pages H1460-H1467Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpheart.00700.2002
Keywords
monoamine oxidases; oxidative stress
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Oxidative stress is one of the factors involved in age-related impairment of cardiac function. In the present study, we investigated the role of the catecholamine-degrading enzyme monoamine oxidase (MAO) in H2O2 production in the hearts of young, adult, and old rats. MAO-dependent H2O2 production, measured by a chemiluminescence-based assay, increased with age, reaching the maximum in 24-mo-old rats (7.5-fold increase vs. 1-mo-old rats). The following observations indicate that the age-dependent increase in H2O2 generation was fully related to the MAO-A isoform: 1) at all the ages tested, chemiluminescence production was inhibited by the MAO-A inhibitor clorgyline but not by the MAO-B inhibitor RO-19 6327; 2) enzyme assay, Western blot, and semiquantitative RT-PCR analysis showed an age-dependent increase in cardiac MAO-A activity, immunodetection, and mRNA expression, respectively; and 3) the MAO-B isoform was undetectable by enzyme assay and Western blot analysis. These results suggest that MAO-A could be a major source of H2O2 in the aging heart.
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