Oxygen consumption in perfused skeletal muscle. Effect of perfusion with aged, fresh and aged-rejuvenated erythrocytes on oxygen consumption, tissue metabolites and inhibition of glucose utilization by acetoacetate.

1. O2 consumption, glucose metabolism and the energy status of skeletal muscle were compared in isolated rat hindquarters perfused with aged (21--35 days), fresh and aged-rejuvenated human erythrocytes. 2. The age of the erythrocytes did not affect O2 consumption, glucose utilization or lactate release either at rest or during exercise. The concentrations of ATP, phosphocreatine and lactate within the muscle were also unaffected by the use of aged erythrocytes. 3. Perfusion with acetoacetate did not inhibit glucose utilization; but, it caused a marked increase in the tissue concentration of citrate in the soleus, a slow-twitch red muscle, and a smaller increase in the gastrocnemius, which contains fast-twitch red and white fibres. Results were similar in hindquarters perfused with aged and aged-rejuvenated erythrocytes. 4. These findings suggest that perfusion with aged human erythrocytes does not cause major alterations in the metabolic performance of the isolated rat hindquarter.