Reduced (1)H-NMR visibility of creatine in isolated rat hearts.
Schneider J., Fekete E., Weisser A., Neubauer S., von Kienlin M.
The aim of this study was to measure the concentration of creatine in Langendorff perfused rat hearts, both by quantitative (1)H-MRS and by high-pressure liquid chromatography (HPLC). First, the relaxation times and other parameters affecting absolute quantification by MRS were determined. At 11.75 T, the relaxation times of myocardial creatine were T(1) = 1.1+/-0.29 sec (mean +/- SD, n = 5) and T(2) = 56.4+/-6.2 ms (n = 9). In phantom experiments the MRS measurements gave accurate values for the known relative concentrations of the detected substances. In glucose-perfused rat hearts, the creatine concentration measured by HPLC was 14.2+/-1.9 mmol/kg wet weight (n = 8), in good agreement with literature values. The (1)H-MRS measurements, however, resulted in creatine concentrations of only approximately 60% of this value. The application of CHESS-pulses for water suppression led to a further 30% reduction of the creatine MRS signal. These results indicate a reduced (1)H-NMR visibility of creatine in the myocardium, which suggests a compartmentation of myocardial creatine into various pools.