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Hypoxaemia increases the accumulation of inosine monophosphate (IMP) in human skeletal muscle during submaximal exercise

1989; Wiley; Volume: 136; Issue: 2 Linguagem: Inglês

10.1111/j.1748-1716.1989.tb08653.x

1365-201X

Kent Sahlin, A. Katz,

High Altitude and Hypoxia

The effect of hypoxaemia on the muscle content of inosine monophosphate (IMP) during short‐term, low‐intensity exercise has been investigated. Six men cycled twice for 5 min at 120 ± 6 W (mean ± SE), which corresponded to ˜ 50% of their maximal normoxic O 2 uptake, breathing air (N) on one occasion and 11% O 2 in N 2 (H) on the other. Oxygen uptake at the end of the exercise period was similar between treatments. No significant difference was observed between H and N in the muscle metabolite contents at rest. Muscle content of phosphocreatine (PCr) decreased and lactate increased during exercise. Post‐exercise PCr during H was 80% of the value during N ( P > 0.05) and post‐exercise muscle lactate was fourfold higher during H than during N ( P < 0.001). Post‐exercise muscle content of ADP was significantly higher during H than during N ( P < 0.01), while ATP and AMP remained constant under both H and N exercise ( P > 0.05 H vs N). IMP was not detectable in pre‐exercise muscle samples (< 0.01 mmol kg ‐1 dry wt) but increased during N exercise (0.03 ± 0.01 mmol kg ‐1 dry wt, P < 0.05) and even more during H exercise (0.16 ± 0.05 mmol kg ‐1 dry wt, P 0.05, H vs N). Post‐exercise IMP was negatively related to PCr (r = ‐0.90) and positively related to lactate ( r = 0.88). It is concluded that hypoxaemia results in an enhanced accumulation of IMP during submaximal exercise and that the IMP level is related to the degree of anaerobic energy utilization.