Lactate-proton cotransport in skeletal muscle.
Skeletal muscle and most other tissues possess a membrane transport system mediating a coupled lactate and H+ translocation. Muscle possesses several lactate-proton transporter isoforms of which two have been cloned; however, the main isoform remains to be identified. The isoforms may have different properties and functional roles, but these have not been specifically characterized. The distribution of lactate-proton transport capacity in skeletal muscle is fiber type dependent, with a higher capacity in slow-twitch fibers compared with fast-twitch fibers. During intense muscle activity and in the recovery period, the lactate and H+ effluxes are mainly mediated by the lactate-proton transporter, which reduces the accumulation of lactate in muscle as well as the drop in internal pH suggested to be involved in muscle fatigue. Thus the lactate-proton transporter is of functional importance for pH regulation in association with muscle activity. This carrier is also important for lactate uptake into resting muscle and other tissues; therefore, the carrier distribution is important for the fate of lactate in the body. In addition, the capacity of the lactate-proton transporter can be increased by intense training and is reduced by inactivity; thus the lactate-proton transporter can undergo adaptive changes.
Juel
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Copenhagen Muscle Research Centre, August Krogh Institute, University of Copenhagen, Denmark.
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D015444:Exercise; D006706:Homeostasis; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000378:metabolism; D027501:Monocarboxylic Acid Transporters; D018482:Muscle, Skeletal / Q000378:metabolism*
D002352:Carrier Proteins; D008565:Membrane Proteins; D027501:Monocarboxylic Acid Transporters