Developmental regulation of insulin-like growth factor-I-stimulated glucose transporter in rat brain astrocytes.
Astrocytic glial cells from 1- and 21-day-old rat brains were established in primary culture to study the expression of insulin-like growth factor-I (IGF-I) receptors and IGF-I-stimulated glucose transporter (Glut-1). Astrocytes from both age groups expressed specific high affinity IGF-I receptors, whose relative affinities for IGF-I, IGF-II, and insulin were comparable. However, the total number of binding sites and IGF-I receptor mRNA levels were 148% and 240% higher in astrocytes from 21-day-old compared with 1-day-old brains. IGF-I caused a dose-dependent stimulation of [3H]2-deoxy-D-glucose [( 3H]dGlc) uptake in astrocytes from 1-day-old brains. This was associated with increases in Glut-1 protein and mRNA levels. In contrast, astrocytes from 21-day-old brains exhibited a 58% decrease in the binding capacity and a 77% decrease in the steady state levels of Glut-1 protein and its mRNA. In addition, IGF-I failed to stimulate the Glut-1 system in these cells. This lack of IGF-I effect is not due to an alteration inherent to the Glut-1 system, since 12-O-tetradecanoyl-phorbol-13-acetate stimulated [3H]dGlc uptake and Glut-1 protein and its mRNA levels. These observations suggest that changes in basal and IGF-I-stimulated Glut-1 system in brain astrocytes may be developmentally regulated.
Masters
B A
BA
Department of Physiology, University of Florida College of Medicine, Gainesville 32610.
Werner
H
H
Roberts
C T
CT
LeRoith
D
D
Raizada
M K
MK
D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development / Q000378:metabolism; D001253:Astrocytes / Q000378:metabolism*; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011956:Receptors, Cell Surface / Q000235:genetics; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D013755:Tetradecanoylphorbol Acetate