Manganese Dipyridoxyl Diphosphate: MRI Contrast Agent with Antioxidative and Cardioprotective Properties?: In Vitroandex VivoAssessments

Manganese dipyridoxyl diphosphate (MnDPDP) is a contrast agent for magnetic resonance imaging (MRI) of the liver. Aims of the study were to examine if MnDPDP possesses superoxide dismutase (SOD) mimetic activityin vitro,and if antioxidant protection can be demonstrated in anex vivorat heart model. Superoxide (•O−2) and hydroxyl radicals (•OH−) were generated in xanthine oxidase and Fenton reactions. Spin adducts with 5,5-dimethyl-1-pyrroline-N-oxide were detected by electron spin resonance spectroscopy. Contractile function and enzyme release were monitored in rat hearts during hypoxia-reoxygenation. Low μM concentrations of MnDPDP and its metabolite Mn dipyridoxyl ethylene-diamine (MnPLED) dismutated•O−2, but showed no activity in Fenton or catalase reactions. MnDPDP 30 μM improved contractile function and reduced enzyme release in rat hearts during reoxygenation. It is concluded that MnDPDP and MnPLED possess SOD mimetic activities and may thereby protect the heart in oxidative stress.