Role of the lactate transporter (MCT1) in skeletal muscles.
We used an antibody, constructed against the monocarboxylate transporter 1 (MCT1) protein (L. Carpenter, R. C. Poole, and A. P. Halestrap. Biochim. Biophys. Acta 1279: 157-165, 1996), to study the expression and role of MCT1 in rat skeletal muscles. MCT1 was higher in red than in white muscles (P < 0.05) and was highly correlated with the oxidative fiber content (%slow-twitch oxidative + %fast-twitch oxidative glycolytic) of skeletal muscles (r = 0.91). MCT1 was highly related to lactate uptake in skeletal muscles (r = 0.90). Total lactate dehydrogenase (LDH) activity, an index of glycolysis, was negatively correlated with MCT1 in rat muscles (r = -0.80). MCT1 was also strongly correlated with the heart-type forms of LDH (LDH-1 vs. MCT1, r = 0.83; LDH-2 vs. MCT1, r = 0.89). There was no relationship between MCT1 and the muscle form of LDH (LDH-5; P > 0.05). MCT1 was highly correlated with citrate synthase activity, a marker of the oxidative capacity of muscle (r = 0.82). Therefore, MCT1 may have kinetics that favor the uptake of L-lactate into the muscle cell for oxidative metabolism, and MCT1 may be coordinately expressed with the heart forms of LDH and enzymes of oxidative metabolism.
McCullagh
K J
KJ
Department of Anatomy, Trinity College Dublin, Ireland.
Poole
R C
RC
Halestrap
A P
AP
O'Brien
M
M
Bonen
A
A
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002950:Citrate (si)-Synthase / Q000378:metabolism; D006614:Hindlimb; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D027501:Monocarboxylic Acid Transporters; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D010477:Perfusion; D051381:Rats; D017207:Rats, Sprague-Dawley
D002352:Carrier Proteins; D008565:Membrane Proteins; D027501:Monocarboxylic Acid Transporters; D019344:Lactic Acid; D007770:L-Lactate Dehydrogenase; D002950:Citrate (si)-Synthase