Restoration of contractile properties of iron-loaded cardiomyocytes by chelators. A 7-day culture of cardiomyocytes kept in DMEM medium at 37°C was followed microscopically by phase contrast and contractility assessed by monitoring changes in light intensity within selected cellular areas lying in the plane of contraction. A shows in sequence (top to bottom) the tracings in terms of optical density (OD, in arbitrary units [au]) of cells followed for 120 seconds at the end of treatment with (1) medium (+none) to which was added in sequence: (2) 10 μM Fe-hydroxyquinoline for 60 minutes (+FHQ); (3) deferrioxamine (100 μM) for 60minutes (+FHQ+DFO) and either (4) deferiprone (100 μM) (+FHQ+DFO+DFP) for 60 minutes, or (5) deferasirox (100 μM) for 60 minutes (+FHQ+ DFO+DFR). B shows beating frequency, expressed as beats/min, representing the frequency of spikes (solid line) and mean amplitude, calculated from the mean heights of the spikes in each trace shown in the top graph and expressed in arbitrary units (au; broken line). The various agents were added sequentially at the time indicated by the respective arrow, and contractility was measured 60 minutes later.