Reduction in myocardial high energy phosphate spin lattice relaxation times using manganese

Paramagnetic contrast agents are being widely used in proton magnetic resonance imaging. The present study demonstrates the potential usefulness of paramagnetic contrast agents in 31P NMR spectroscopy. Using the Langendorff perfused rat heart, manganese chloride (Mn2+) at a concentration of 50 microM/L was added to the perfusate for 10 or 30 min. 31P NMR T1 relaxation times were subsequently measured at 121.5 MHz. After the 10 min exposure to Mn2+, 31P NMR T1 measurements of phosphocreatine and ATP were reduced by ca 25 and 50%, respectively, with no significant change in linewidths. A small additional decrease in T1 relaxation times after infusion of Mn2+ for 30 min was not significantly different from the values at 10 min. Potential uses of Mn2+ in 31P NMR spectroscopy include improving the S/N ratio of spectra and assessment of calcium ion channel activity.