BLOOD-FLOW AND OXYGEN-UPTAKE IN ISOLATED CANINE SKELETAL-MUSCLE DURING ACUTE ANEMIA

The metabolic demands placed on the oxygen transport system by skeletal muscle during acute anemia were studied in 16 anesthetized dogs. Venous outflow from the gastrocnemius-plantaris muscle was isolated. Muscle blood flow and oxygen uptake, cardiac output (Q), and total body oxygen uptake (VO2) were obtained during a control period and at 30 min of anemia (Hct = 14%). Eight animals (treated group) received propranolol prior to the control sample; the remaining eight animals (untreated) did not receive the drug. During anemia Q increased by about 90% in both groups; the value for Q in the untreated group was higher (P < 0.05). Muscle blood flow also increased in both series during anemia. VO2 was not different between the groups and was constant throughout the experiment. Although muscle oxygen delivery was less than 50% of the preanemic control in both groups, muscle oxygen uptake increased from 5.1 to 7.4 μl/g/min during anemia in the untreated series (P < 0.05). This change did not occur in the propranolol-treated animals. The data demonstrated that in acute anemia skeletal muscle increased its demands on the oxygen transport system; the increase in muscle oxygen uptake occurred at the expense of other tissues; and the rise in muscle oxygen uptake was prevented by β-blockade.