Monocarboxylic acid transporters, MCT1 and MCT2, in cortical astrocytes in vitro and in vivo.
We used sequence-specific antibodies to characterize two monocarboxylic acid transporters, MCT1 and MCT2, in astrocytes. Both proteins are expressed in primary cultures of cortical astrocytes, as indicated by immunoblotting and immunofluorescence. Both MCT1 and MCT2 are present in small, punctate structures in the cytoplasm and at the cell membrane. Cells showing very low levels of labeling for glial fibrillary acidic protein (GFAP) also label more dimly for MCT2, but not for MCT1. In vivo, double-label immunofluorescence studies coupled with confocal microscopy indicate that MCT1 and MCT2 are rare in astrocytes in the cortex. However, they are specifically labeled in astrocytes of the glial limiting membrane and in white matter tracts. Both transporters are also present in the microvasculature. Comparison of labeling for MCT1 and MCT2 with markers of the blood-brain barrier shows that the transporters are not always limited to the astrocytic endfeet in vivo. Our results suggest that the level of expression of monocarboxylic acid transporters MCT1 and MCT2 by cortical astrocytes in vivo is significantly lower than in vitro but that astrocytes in some other regions of the brain can express one or both proteins in significant amounts.
Hanu
R
R
Department of Physiology, School of Medicine, University of Maryland, Baltimore, Maryland 21201, USA.
McKenna
M
M
O'Neill
A
A
Resneck
W G
WG
Bloch
R J
RJ
D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D001812:Blood-Brain Barrier; D002264:Carboxylic Acids / Q000378:metabolism; D002352:Carrier Proteins / Q000276:immunology / Q000378:metabolism*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000378:metabolism*; D005904:Glial Fibrillary Acidic Protein / Q000276:immunology / Q000378:metabolism; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D027501:Monocarboxylic Acid Transporters; D051381:Rats
D002264:Carboxylic Acids; D002352:Carrier Proteins; D005904:Glial Fibrillary Acidic Protein; D027501:Monocarboxylic Acid Transporters; C091633:Slc16a7 protein, rat