Accuracy of 1H and 31P MRS analyses of lactate in skeletal muscle

As the end product of anaerobic metabolism and a source of H+, lactic acid is important in metabolism and pH regulation. Several methods have been introduced to calculate changes in the lactate anion (Lac(-)) concentration in exercising skeletal muscle from information derived from the P-31 spectrum. Alternatively, Lac(-) may be observed directly with H-1 MRS. Both H-1 and P-31 spectroscopy have potential problems, which could prevent accurate determination of [Lac(-)]. It is demonstrated that quantitatively accurate H-1 MRS measurements of changes in [Lac(-)] due to exercise are possible in isolated muscle. In general, calculation by P-31 MRS overestimates Lac(-) production. An analysis is presented of possible sources of errors in the H-1 and P-31 MRS methods. (C) 2000 Wiley-Liss, Inc.