Inhibition of the Sodium-Calcium Exchanger by SEA0400 Inhibits Manganese Efflux from Isolated Hearts

Methods Heart Perfusion Protocol Male Sprague Dawley rats were anesthetized. The heart was excised, cannulated, and perfused with Krebs-Henseleit buffer equilibrated with 95% O2 5% CO2 at 370C. A water-filled latex balloon was inserted into the left ventricle and connected to a pressure transducer to record the left ventricular pressure and heart rate. The rate-pressure product (RPP) was used as an index of workload. The perfusion column was placed in a vertical bore 9.4T Bruker scanner. Once the setup was finished, the heart was paced at 360 beats/min and the perfusate was switched to modified Krebs-Henseleit buffer containing 30 μM MnCl2 for 30 min (washin period), followed by a 30 min washout period without MnCl2. There were three experimental groups: 1) control: hearts perfused with Mn only (n=5); 2) SEA0400_washin: hearts perfused with 1 μM SEA0400, an NCX inhibitor, during the washin period (n=6); and 3) SEA0400_washout: hearts perfused with 1 μM SEA0400 during the washout period (n=6).