Poustis-Delpont C, Mengual R, Sudaka P
Laboratoire de Biochimie, Faculté de Médecine, Nice, France.
Am J Physiol. 1988 Dec;255(6 Pt 2):F1249-55. 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.
通过在微载体珠上密集培养获得的LLC-PK1细胞顶端膜囊泡对L-[³H]乳酸的摄取进行了表征。顶端膜制备技术涉及MgCl₂沉淀。仅在汇合后才出现Na⁺依赖性L-[³H]乳酸摄取；其出现与顶端膜中氨肽酶的亚细胞定位平行。L-[³H]乳酸摄取是Na⁺依赖性且具有电生性的。L-[³H]乳酸摄取中只有Na⁺依赖性成分可被一类独立载体饱和。表观亲和力常数为1.1±0.25 mM，表观最大速度为29±3 nmol·mg⁻¹·min⁻¹。Na⁺-乳酸共转运化学计量为2个Na⁺对应1个乳酸。L-乳酸转运系统的特异性与先前在肾皮质刷状缘膜中描述的单羧酸途径的特异性相符，且与三羧酸载体、D-葡萄糖转运体和阴离子的一般途径不同。LLC-PK1细胞系似乎是研究L-乳酸摄取调节和肾单羧酸转运体生物合成的有用工具。
