LLC-PK1 cells express Na+-lactate cotransport in apical membranes after confluency.
L-[3H]lactate uptake was characterized in LLC-PK1 cell apical membrane vesicles obtained by intensive culture on microcarrier beads. The apical membrane preparation technique involved MgCl2 precipitation. Na+-dependent L-[3H]lactate uptake was present only after confluency; its appearance paralleled the subcellular localization of aminopeptidase in apical membranes. L-[3H]lactate uptake was Na+-dependent and electrogenic. Only the Na+-dependent component of L-[3H]lactate uptake was saturable with one family of independent carriers. The apparent affinity constant was 1.1 +/- 0.25 mM and the apparent maximal velocity was 29 +/- 3 nmol.mg-1.min-1. The Na+-lactate cotransport stoichiometry was 2 Na+ for 1 lactate. The specificity of the L-lactate transport system was compatible with that of the monocarboxylic acid pathway described previously in brush-border membranes of kidney cortex and discrete from the tricarboxylic acid carrier, the D-glucose transporter, and the general pathway for anions. The LLC-PK1 cell line appears to be a useful tool for study of the regulation of L-lactate uptake and biosynthesis of the renal monocarboxylic acid transporter.
Poustis-Delpont
C
C
Laboratoire de Biochimie, Faculté de Médecine, Nice, France.
Mengual
R
R
Sudaka
P
P
D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D007700:Kinetics; D007773:Lactates / Q000378:metabolism*; D027501:Monocarboxylic Acid Transporters; D012964:Sodium / Q000378:metabolism*; D027981:Symporters
D002352:Carrier Proteins; D007773:Lactates; D027501:Monocarboxylic Acid Transporters; D027981:Symporters; C056939:sodium lactate cotransporter; D012964:Sodium