THE LACTATE SHUTTLE
Brooks, G. A. (1986). Lactate production under fully aerobic conditions: The lactate shuttle duing rest and exercise. Federation Proceedings, 45, 2924-2929.
Oxygen insufficiency and other factors increase the rate of lactate production. Significant quantities of lactate are produced under postabsorptive as well as postprandial conditions in resting individuals.
During sustained submaximal (in terms of VO2max) exercise, the rates of lactate production (Ri) and oxidation (Rox) are greatly elevated compared to rest. However, lactate production and oxidation increase relatively less than oxygen consumption during moderate-intensity exercise. Because the lactate production index (RiI = Ri / VO2) decreases during submaximal moderate-intensity exercise compared to rest, skeletal muscle and other sites of lactate production are effectively oxygenated.
Lactate production occurs despite an apparent abundance of oxygen. Similarly, glucose catabolism in the human brain results in lactate production. The formation of lactate under fully aerobic conditions of rest and exercise represents an important mechanism by which different tissues share a carbon source (lactate) for oxidation and other processes such as gluconeogenesis. That mechanism has been termed the "lactate shuttle."
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