Muscle adenine nucleotide metabolism during and in recovery from maximal exercise in humans

The relationship between changes in the muscle total adenine nucleotide poo l (TAN = ATP + ADP + AMP) and IMP during and after 30 s of sprint cycling w as examined. Skeletal muscle samples were obtained from the vastus laterali s muscle of seven untrained men (23.9 +/- 2.3 yr, 74.4 +/- 3.6 kg, and 55.0 +/- 2.9 ml kg(-1) min(-1) peak oxygen consumption) before and immediately after exercise and after 5 and 10 min of passive recovery. The exercise-ind uced increase in muscle IMP was linearly related to the decrease in muscle TAN (r = -0.97, P < 0.01), and the slope of this relationship (-0.83) was n ot different from 1.0 (P > 0.05), indicating a 1:1 stoichiometric relations hip. This interpretation must be treated cautiously, because all subjects d isplayed a greater decrease in TAN compared with the increase in IMP conten t, and the TAN + IMP + inosine + hypoxanthine content was lower (P < 0.05) immediately after exercise compared with during rest. During the first 5 mi n of recovery, the increase in TAN was not correlated with the decrease in IMP (r = -0.18, P > 0.05). In all subjects, the magnitude of TAN increase w as higher than the magnitude of IMP decrease over this recovery period. In contrast, the increase in TAN was correlated with the decrease in IMP throu ghout the second 5 min of recovery (r = -0.80, P < 0.05), and it was a 1:1 stoichiometric relationship (slope = -1.12). These data indicate that a sma ll proportion of the TAN pool was temporarily lost from the muscle purine s tores during sprinting but was rapidly recovered after exercise.