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

The relationship between changes in the muscle total adenine nucleotide pool (TAN = ATP + ADP + AMP) and IMP during and after 30 s of sprint cycling was examined. Skeletal muscle samples were obtained from the vastus lateralis muscle of seven untrained men (23.9 ± 2.3 yr, 74.4 ± 3.6 kg, and 55.0 ± 2.9 ml ⋅ kg−1 ⋅ min−1peak oxygen consumption) before and immediately after exercise and after 5 and 10 min of passive recovery. The exercise-induced increase in muscle IMP was linearly related to the decrease in muscle TAN ( r = −0.97, P 0.05), indicating a 1:1 stoichiometric relationship. This interpretation must be treated cautiously, because all subjects displayed a greater decrease in TAN compared with the increase in IMP content, and the TAN + IMP + inosine + hypoxanthine content was lower ( P 0.05). In all subjects, the magnitude of TAN increase was higher than the magnitude of IMP decrease over this recovery period. In contrast, the increase in TAN was correlated with the decrease in IMP throughout 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 small proportion of the TAN pool was temporarily lost from the muscle purine stores during sprinting but was rapidly recovered after exercise.