Reduced H-1-NMR visibility of creatine in isolated rat hearts

The aim of this study was to measure the concentration of creatine in Lange ndorff perfused rat hearts, both by quantitative H-1-MRS and by high-pressu re liquid chromatography (HPLC). First, the relaxation times and other para meters 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 experimen ts the MRS measurements gave accurate values for the known relative concent rations of the detected substances. In glucose-perfused rat hearts, the cre atine concentration measured by HPLC was 14.2 +/- 1.9 mmol/kg wet weight (n = 8), in good agreement with literature values. The H-1-MRS measurements, however, resulted in creatine concentrations of only approximately 60% of t his value. The application of CHESS-pulses for water suppression led to a f urther 30% reduction of the creatine MRS signal. These results indicate a r educed H-1-NMR visibility of creatine in the myocardium, which suggests a c ompartmentation of myocardial creatine into various pools. (C) 2000 Wiley-L iss, Inc.