Lactate and glucose metabolism in mouse (Mus musculus) and reptile (Anolis carolinensis) skeletal muscle.
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.
Wickler
S J
SJ
Department of Animal and Veterinary Science, California State Polytechnic University, Pomona 91768.
Gleeson
T T
TT
D000818:Animals; D002950:Citrate (si)-Synthase / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D006003:Glycogen / Q000378:metabolism; D007700:Kinetics; D007773:Lactates / Q000378:metabolism*; D019344:Lactic Acid; D008116:Lizards / Q000378:metabolism*; D008297:Male; D051379:Mice; D009132:Muscles / Q000378:metabolism*; D010084:Oxidation-Reduction; D005082:Physical Exertion / Q000502:physiology
D007773:Lactates; D019344:Lactic Acid; D006003:Glycogen; D002950:Citrate (si)-Synthase; D005947:Glucose