Determinants of deoxyglucose uptake in cultured astrocytes: the role of the sodium pump.
Glucose utilization in primary cell cultures of mouse cerebral astrocytes was studied by measuring uptake of tracer concentrations of [3H]2-deoxyglucose ([3H]2-DG). The resting rate of glucose utilization, estimated at an extracellular K+ concentration ([K+]o) of 5.4 mM, was high (7.5 nmol glucose/mg protein/min) and was similar in morphologically undifferentiated and "differentiated" (dibutyryl cyclic AMP-pretreated) cultures. Resting uptake of [3H]2-DG was depressed by ouabain, by reducing [K+]o, and by cooling. These observations suggest that resting glucose utilization in astrocytes was dependent on sodium pump activity. Sodium pump-dependent uptake in 2-3-week-old cultures was about 50% of total [3H]2-DG uptake but this fraction declined with culture age from 1 to 5 weeks. Uptake was not affected by changes in extracellular bicarbonate concentration ([HCO3-]o) in the range of 5-50 mM but was significantly reduced in bicarbonate-free solution. At high [HCO3-]o (50 mM) uptake was insensitive to pH (pH 6-8), whereas at low [HCO3-]o (less than 5 mM) uptake was markedly pH-dependent. Elevation of [K+]o from 2.3 mM to 14.2-20 mM (corresponding to extremes of the physiological range of [K+]o) resulted in a 35-43% increase in [3H]2-DG uptake that was not affected by culture age or by morphological differentiation. Our results indicate a high apparent rate of glucose utilization in astrocytes. This rate is dynamically responsive to changes in extracellular K+ concentration in the physiological range and is partially dependent on sodium pump activity.
Brookes
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N
Yarowsky
P J
PJ
D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D001639:Bicarbonates / Q000494:pharmacology; D003994:Bucladesine / Q000494:pharmacology; D002478:Cells, Cultured; D003080:Cold Temperature; D003837:Deoxy Sugars / Q000378:metabolism*; D003847:Deoxyglucose / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D051379:Mice; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000378:metabolism*
D001639:Bicarbonates; D003837:Deoxy Sugars; D007473:Ion Channels; D010042:Ouabain; D003994:Bucladesine; D003847:Deoxyglucose; D012964:Sodium; D011188:Potassium