TY - JOUR
T1 - Glutamate triggers rapid glucose transport stimulation in astrocytes as evidenced by real-time confocal microscopy
AU - Loaiza, Anitsi
AU - Porras, Omar H.
AU - Barros, Luis Felipe
PY - 2003/8/13
Y1 - 2003/8/13
N2 - Glutamate stimulates glycolysis in astrocytes, a phenomenon that couples astrocytic metabolism with neuronal activity. However, it is not known whether glutamate also affects glucose transporter-1 (GLUT 1), the transporter responsible for glucose entry into astrocytes. To address this question, two different real-time single-cell hexose uptake assays were applied to cultured hippocampal astrocytes using confocal epifluorescence microscopy. Glutamate caused a twofold to threefold increase in the zero-trans uptake rates of the fluorescent hexoses 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose (2-NBDG) and 6-[N-(7-nitrobenz-2-oxa-1,3-diazol-4yl)amino]-6-deoxyglucose (6-NBDG). Galactose uptake, determined by the calcein volumetric assay, was stimulated to a similar extent, confirming the fluorescent hexose data, and also demonstrating that glutamate stimulation is a Vmax effect. Remarkably, glucose transport stimulation developed fully inside 10 sec, which is 100 times faster than acute stimulations of glucose transport in other cell types. Glutamate did not significantly affect the rate of 6-NBDG uptake by GLUT1-expressing epithelial Clone 9 cells, suggesting that an astrocyte-specific factor is required for transport stimulation. We conclude that glucose transport stimulation occurs early during astrocytic activation by glutamate, which provides a novel regulatory node to current models of brain energy metabolism. This mechanism should also be considered for the interpretation of functional imaging data based on hexoses.
AB - Glutamate stimulates glycolysis in astrocytes, a phenomenon that couples astrocytic metabolism with neuronal activity. However, it is not known whether glutamate also affects glucose transporter-1 (GLUT 1), the transporter responsible for glucose entry into astrocytes. To address this question, two different real-time single-cell hexose uptake assays were applied to cultured hippocampal astrocytes using confocal epifluorescence microscopy. Glutamate caused a twofold to threefold increase in the zero-trans uptake rates of the fluorescent hexoses 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose (2-NBDG) and 6-[N-(7-nitrobenz-2-oxa-1,3-diazol-4yl)amino]-6-deoxyglucose (6-NBDG). Galactose uptake, determined by the calcein volumetric assay, was stimulated to a similar extent, confirming the fluorescent hexose data, and also demonstrating that glutamate stimulation is a Vmax effect. Remarkably, glucose transport stimulation developed fully inside 10 sec, which is 100 times faster than acute stimulations of glucose transport in other cell types. Glutamate did not significantly affect the rate of 6-NBDG uptake by GLUT1-expressing epithelial Clone 9 cells, suggesting that an astrocyte-specific factor is required for transport stimulation. We conclude that glucose transport stimulation occurs early during astrocytic activation by glutamate, which provides a novel regulatory node to current models of brain energy metabolism. This mechanism should also be considered for the interpretation of functional imaging data based on hexoses.
KW - 2-NBDG
KW - 6-NBDG
KW - Calcein
KW - Galactose
KW - Glucose
KW - Membrane transport
UR - http://www.scopus.com/inward/record.url?scp=0042237889&partnerID=8YFLogxK
U2 - 10.1523/jneurosci.23-19-07337.2003
DO - 10.1523/jneurosci.23-19-07337.2003
M3 - Article
C2 - 12917367
AN - SCOPUS:0042237889
SN - 0270-6474
VL - 23
SP - 7337
EP - 7342
JO - Journal of Neuroscience
JF - Journal of Neuroscience
IS - 19
ER -