Metabolic adaptation to reduced muscle blood flow. II. Mechanisms and beneficial effects.

Increased mitochondrial enzyme activities are induced in rat muscles after common iliac artery ligation, giving a 76-93% blood flow reduction, and 6 days of intermittent muscle stimulation. To elucidate the trigger for this enzyme induction, the acute alterations in the metabolite pattern during contractions were evaluated. More pronounced changes in intramuscular PO2, creatine phosphate, ATP/ADP, lactate/pyruvate, and glycogen were observed in the ligated leg. The benefit of this enzyme alteration was investigated with the hindlimb perfusion technique. Enzymatically adapted and control legs were perfused at reduced flow during contractions. Similar oxygen consumption and glucose uptake but a significantly lower lactate release were observed in the adapted legs. A lower lactate level, lactate/pyruvate, and a better maintained creatine phosphate/creatine were found in the adapted soleus muscle. The results demonstrate that the increase of mitochondrial enzymes is preceded by acute alterations in energy metabolites due to intermittent hypoxia during contractions at reduced flow and that this enzyme adaptation allows the muscle tissue to maintain a lower anaerobic metabolism and a better energy state during exercise.