LLC-PK1 cells express Na+-lactate cotransport in apical membranes after confluency

• Published in: The American journal of physiology Vol. 255; no. 6 Pt 2; pp. F1249 - F1255
• Main Authors: Poustis-Delpont, C, Mengual, R, Sudaka, P
• Format: Journal Article
• Language: English
• Published: United States 01-12-1988
• Subjects: Animals; Biological Transport; Carrier Proteins - metabolism; Cell Line; Cell Membrane - metabolism; Kinetics; Lactates - metabolism; Monocarboxylic Acid Transporters; Sodium - metabolism; Symporters
• ISSN: 0002-9513
• DOI: 10.1152/ajprenal.1988.255.6.f1249

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.