Postnatal alteration of monocarboxylate transporter 1 expression in the rat corpus callosum

In the central nervous system (CNS), monocarboxylate transporter 1 (MCT1) is expressed in astrocytes and endothelial cells but also in oligodendroglia. Oligodendroglia support neurons and axons through lactate transportation by MCT1. Limited information is available on the MCT1 expression changes in candidate cells in the developing rat brain, especially in corpus callosum which is the most vulnerable area in demyelinating diseases. In the present study, we investigated the expression pattern of MCT1 during postnatal development in the rat corpus callosum using immunofluorescene staining, Western blotting analysis and RT-PCR. We reported that MCT1 gene and protein were consistently expressed in the rat corpus callosum from birth to adult. MCT1/CNPase and MCT1/GFAP immunofluorescence staining demonstrated that most of MCT1 positive cells were co-labeled with cyclic nucleotide 3´ phosphodiesterase (CNPase) in rat corpus callosum from P7 to adult, whereas MCT1(+)/GFAP(+) cells preserve the dominate position before P7. Moreover, there were significant associations between the expression of MCT1 protein and the expression of myelin basic protein (MBP) (correlation coefficient: r=0.962, P=0.009) from P7 to adult. Similarly, the MCT1 mRNA expression was also significantly associated with MBP mRNA expression (r=0.976, P=0.005). Our results are proposing that in the developing brain white matter, MCT1 is predominately expressed in oligodendrocyte though it mainly expressed in astrocyte in early postnatal, which indicate that MCT1 may involve in the oligodendrocyte development and myelination.