NMR AND ANALYTIC BIOCHEMICAL EVALUATION OF CRP AND NUCLEOTIDES IN THEHUMAN CALF DURING MUSCLE-CONTRACTION

This study compared biochemical and P-31-nuclear magnetic resonance (N MR) determinations of energy metabolites during isometric contractions of the human calf muscle at various exercise intensities. Seven male subjects performed one-legged isometric contractions at a work load of 28, 64, and 90% of maximal voluntary contraction force (28-, 64-, and 90%-CON, respectively) for 3 min, 40 s, and 40 s, respectively, in a magnet and in an exact model of the magnet with an arrangement for rap id muscle biopsy sampling from the gastrocnemius. The decrease in phos phocreatine (CrP) determined by NMR was 20, 33, and 71% for 28%-, 64%- , and 90%-CON, respectively. These decreases were the same as those de termined biochemically (25,34, and 61%, respectively). Muscle CrP 1 mi n after 90%-CON was also found to be similar between NMR and biochemic al determinations (88 and 74% of resting value, respectively). Althoug h no significant change in muscle ATP was found by NMR, a decrease of 29% was observed biochemically at 90%-CON. The ratio between muscle Cr P and ATP was the same between NMR and biochemical determinations exce pt for 90%-CON (1.98 and 0.78, respectively). The increase in muscle A DP determined by NMR was two-, five-, and eightfold higher than that f ound biochemically for 28%-, 64%-, and 90%-CON, respectively. This was related to the change in muscle inosine monophosphate concentration ( r = 0.61, P < 0.05). The present data suggest that biochemical measure ments and NMR spectroscopy provide the same information on muscle CrP during isometric muscle contractions. This also appears to be true for muscle ATP, with the exception of measurements during muscle contract ions at high work loads. The more pronounced increase in muscle ADP de termined by NMR compared with that determined by biochemical measureme nts is consistent with free ADP being a major modulator of muscle meta bolism during muscle contractions.