title: Pyruvate shuttle in muscle cells: high-affinity pyruvate transport sites insensitive to trans-lactate efflux.
abstract: The specificity of the transport mechanisms for pyruvate and lactate and their sensitivity to inhibitors were studied in L6 skeletal muscle cells. Trans- and cis-lactate effects on pyruvate transport kinetic parameters were examined. Pyruvate and lactate were transported by a multisite carrier system, i.e., by two families of sites, one with low affinity and high capacity (type I sites) and the other with high affinity and low capacity (type II). The multisite character of transport kinetics was not modified by either hydroxycinnamic acid (CIN) or p-chloromercuribenzylsulfonic acid (PCMBS), which exert different types of inhibition. The transport efficiency (TE) ratios of maximal velocity to the trans-activation dissociation constant (Kt) showed that lactate and pyruvate were preferentially transported by types I and II sites, respectively. The cis-lactate effect was observed with high Ki values for both sites. The trans-lactate effect on pyruvate transport occurred only on type I sites and exhibited an asymmetric interaction pattern (Kt of inward lactate > Kt of outward lactate). The inability of lactate to trans-stimulate type II sites suggests that intracellular lactate cannot recruit these sites. The high-affinity type II sites act as a specific pyruvate shuttle and constitute an essential relay for the intracellular lactate shuttle.
authors.affiliation: Laboratoire de Physiologie des Adaptations, Unité de Formation et de Recherche Cochin Port Royal, Université René Descartes, 75014 Paris, France. mengual@unice.fr
authors.forename: Raymond
authors.initials: R
authors.lastname: Mengual
authors.forename: Kaoukib
authors.initials: K
authors.lastname: El Abida
authors.forename: Nassima
authors.initials: N
authors.lastname: Mouaffak
authors.forename: Michel
authors.initials: M
authors.lastname: Rieu
authors.forename: Michele
authors.initials: M
authors.lastname: Beaudry
mesh_terms: D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D019344:Lactic Acid / Q000378:metabolism*; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D010666:Phenylpropionates / Q000494:pharmacology; D011485:Protein Binding; D019289:Pyruvic Acid / Q000493:pharmacokinetics*; D051381:Rats; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
chemical_list: D010666:Phenylpropionates; D019344:Lactic Acid; C035253:3-phenylpropionic acid; D002731:4-Chloromercuribenzenesulfonate; D019289:Pyruvic Acid