Glucose-dependent regulation of glucose transport activity, protein, and mRNA in primary cultures of rat brain glial cells.
D-Glucose deprivation of primary rat brain glial cell cultures, by incubation with 25 mM D-fructose for 24 h, resulted in a 4-5-fold induction of D-glucose transport activity. In contrast, 24-h D-glucose starvation of primary rat brain neuronal cultures had only a marginal effect (1.5-2-fold) on D-glucose transport activity. Northern blot analysis of total cellular RNA demonstrated that under these conditions the rat brain glial cells specifically increased the steady-state level of the D-glucose transporter mRNA 4-6-fold, whereas Northern blot analysis of the neuronal cell cultures revealed no significant alteration in the amount of D-glucose transporter mRNA by D-glucose deprivation. These findings demonstrated that the D-glucose-dependent regulation of the D-glucose transporter system occurred in a brain cell type-specific manner. The ED50 for the D-glucose starvation increase in the D-glucose transporter mRNA, in the glial cell cultures, occurred at approximately 3.5 mM D-glucose with maximal effect at 0.5 mM D-glucose. Readdition of D-glucose to the starved cell cultures reversed the increase in the D-glucose transporter mRNA levels and D-glucose transport activity to control values within 24 h. The increase in the D-glucose transporter mRNA was relatively rapid with half-maximal stimulation at approximately 2 h and maximal induction by 6-12 h of D-glucose deprivation. A similar time course was also observed for the starvation-induced increase in D-glucose transport activity and D-glucose transporter protein, as determined by Western blot analysis. These results document that, in rat brain glial cells, D-glucose transport activity, protein, and mRNA are regulated by the extracellular D-glucose concentration. Further, this suggests a potential role for hyperglycemia in the down-regulation of the D-glucose transport system in vivo.
Walker
P S
PS
Department of Physiology and Biophysics, University of Iowa, Iowa City 52242.
Donovan
J A
JA
Van Ness
B G
BG
Fellows
R E
RE
Pessin
J E
JE
D000818:Animals; D015152:Blotting, Northern; D001921:Brain / Q000166:cytology*; D002478:Cells, Cultured; D005632:Fructose / Q000494:pharmacology; D005947:Glucose / Q000502:physiology*; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009457:Neuroglia / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; D005632:Fructose; D005947:Glucose