A new physiological role of copper amine oxidases: Cardioprotection against reactive oxygen intermediates

The antioxidant effects of serum amine oxidase (SAO) against electrolysis induced oxygen free radicals (̇O₂^-,̇OH, ¹O₂) and their by-products (H₂, O₂, HOCl) were determined in vitro by the DPD (N,N-diethyl-p-phenylenediamine) colorimetric method. SAO (1 μM) displayed a high antioxidant capacity (91%), comparable to that of ceruloplasmine (89%), and higher to that of superoxide dismutase (SOD) in equimolar concentrations (38%). Cardioprotective effects of SAO against oxidative injury, were determined ex vivo on isolated rat hearts (Langendorff), exposed to oxygen free radicals (OFR) generated by electrolysis (10 mA, 1 min) in the absence and presence of different concentrations (0-0.5 μM) of SAO in the Krebs-Henseleit perfusion solutions. Electrocardiogram and left ventricular pressure (LVP), in the non-treated hearts, were altered by OFR formation. In the presence of SAO, a concentration dependent reduction of these alterations was observed. The protective effect afforded by 0.5 μM SAO (cardioprotection of 94%) was slightly higher than that of 1 μM ceruloplasmin (83-89%) and higher than that of 1 μM SOD (20-45%). With BSA, no cardioprotection at all was observed. SAO, a circulating extracellular enzyme for most of mammalians, appears as an effective cardioprotective agent against myocardial injuries generated by OFR.