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Am J Physiol Endocrinol Metab 285: E1196-E1204, 2003. First published August 12, 2003; doi:10.1152/ajpendo.00034.2003
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Pyruvate shuttle in muscle cells: high-affinity pyruvate transport sites insensitive to trans-lactate efflux

Raymond Mengual,2 Kaoukib el Abida,1 Nassima Mouaffak,1 Michel Rieu,1 and Michele Beaudry1

1Laboratoire de Physiologie des Adaptations, Unité de Formation et de Recherche Cochin Port Royal, Université René Descartes, 75014 Paris; and 2Institut de Pharmacologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique, 06560 Sophia Antipolis Valbonne, France

Submitted 23 January 2003 ; accepted in final form 7 August 2003

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.

carrier; monocarboxylate transporter; asymmetric transport; skeletal muscle; lactate


Address for reprint requests and other correspondence: R. Mengual, Institut de Pharmacologie Moleculaire et Cellulaire, CNRS, 660 Route des Lucioles, 06560 Sophia Antipolis Valbonne, France (E-mail: mengual{at}unice.fr).






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