Transport Mechanism for L-Lactic Acid in Human Myocytes Using Human Prototypic Embryonal Rhabdomyosarcoma Cell Line (RD Cells)(Pharmacology)

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Monocarboxylate transporter (MCT), which cotransport L-lactic acid and protons across cell membranes, are important for regulation of muscle pH. However, it has not been demonstrated in detail whether MCT isoform contribute to the transport of L-lactic acid in skeletal muscle. The aim of this study was to characterize L-lactic acid transport using an human rhabdomyosarcoma (RD) cell line as a model of human skeletal muscle. mRNAs of MCT 1, 2 and 4 were found to be expressed in RD cells. The [^<14>C] L-lactic acid uptake was concentration-dependent with a K_m of 1.19mM. This K_m value was comparable to its K_m values for MCT1 or MCT2. MCT1 mRNA was found to be present markedly greater than that MCT2. Therefore, MCT1 most probably acts on L-lactic acid uptake at RD cells. [^<14>C] L-Lactic acid efflux in RD cells was inhibited by α-cyano-4-hydroxycinnamate (CHC) but not by butyric acid, a substrate of MCT1. Accordingly, MCT2 or MCT4 is responsible for L-lactic acid efflux by RD cells. MCT4 mRNA was found to be present significantly greater than that MCT2. We conclude that MCT1 is responsible for L-lactic acid uptake and L-lactic acid efflux is mediated by MCT4 in RD cells.
社団法人日本薬学会の論文
2005-07-01