Double quantum filtered H-1 NMR spectroscopy enables quantification of lactate in muscle

In this study we address the question of quantification of muscle lactate u sing double quantum filtered (DQF) H-1 NMR spectroscopy where dipolar and s calar coupled spectra are acquired. For this, lactate content in muscle sam ples was independently determined using a conventional enzymatic assay and DQF, H-1 NMR spectroscopy. NMR quantification of lactate relied on comparis on of muscle spectra with similarly acquired spectra of standard lactate so lutions. Transverse relaxation, T-2, and dipolar coupling effects were inve stigated at two different orientations of muscle fibers relative to B-o and at various lactate concentrations. In all cases, we found a biexponential T-2 decay of the lactate methyl signal with a long T-2 of 142 ms (+/-8 ms, n=24) and a short T-2 of 37 ms (+/-6 ms, n=24). Lactate content of muscle d etermined by NMR spectroscopy agreed with the results obtained from enzymat ic assays of the same samples provided that T-2 effects as well as the pres ence of both scalar and dipolar coupling interactions of lactate in muscle were taken into account. (C) 2001 Academic Press.