AJP - Regulatory, Integrative and Comparative Physiology, Vol 264, Issue 3 487-R491, Copyright © 1993 by American Physiological Society
Lactate and glucose metabolism in mouse (Mus musculus) and reptile (Anolis carolinensis) skeletal muscle
S. J. Wickler and T. T. Gleeson
Department of Animal and Veterinary Science, California State Polytechnic University, Pomona 91768.
The reliance on anaerobic metabolism during exercise in lizards has been
the subject of a growing body of literature in activity metabolism. Prior
studies have demonstrated that lizards rely more on postexercise lactate to
regenerate depleted glycogen stores than do many mammals. These studies
prompted an in vitro comparison between the metabolic mechanisms for the
handling of lactate and glucose in the muscles of a small mammal and
lizard. Hindlimb muscles of Mus and Anolis were stimulated to fatigue and
then incubated in the presence of 15 mM lactate and either 5.5 (mice) or
8.5 (anoles) mM glucose. Oxidation rates of lactate and glucose were seven
to eight times higher in mice. Both species oxidized more lactate than
glucose (8 to 9 times). However, anole muscle showed a preference for
lactate as a substrate for glycogenesis, incorporating 1.5 times as much
lactate (expressed in glucose equivalents) as glucose. In
contradistinction, mice incorporated 2.8 times as much glucose into
glycogen as lactate. The quantitative differences in metabolic scope of
mammals and reptiles are accompanied by fundamental differences in the
capacity and patterns of skeletal muscle metabolism of lactate and glucose.
