Metabolic adaptation to reduced muscle blood flow. I. Enzyme and metabolite alterations.

A rat model was developed in which the adaptive effects of exposing skeletal muscle tissue to a reduced blood flow during muscle contractions could be studied. The common iliac artery was ligated in one hindlimb, using the other as control. This procedure reduced the exercise blood flow to the individual muscles of the lower limb by 76-93%, evaluated with the microsphere technique. Muscle contractions were induced by electrical stimulation of the sciatic nerves in both legs. After intermittent stimulation for 6 days, a significant increase in citrate synthase and cytochrome c oxidase activities was found in the soleus (26%) and extensor digitorum longus (EDL, 20%) muscles of the ligated legs compared with the control legs. Resting metabolite concentrations were also measured, and a reduction of the ATP level (soleus 35%, EDL 14%) and an increased glycogen content (55-71%) were found. These results demonstrate that a reduced blood flow during muscle contractions provokes an adaptive increase of the oxidative enzyme capacity as well as altered resting levels of intracellular metabolites.