Glucose Transport in Astrocytes: Regulation by Thyroid Hormone

Lm, Roeder; Ib, Williams; Jt, Tildon

doi:10.1111/j.1471-4159.1985.tb07239.x

Cited by 42 publications

(20 citation statements)

References 43 publications

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“…Although there have been very elegant approaches carried out with the giant axons of Loligo, in which the parameters of glucose, 2-deoxyglucose and 3-0-methylglucose transport were studied (Baker & Carruthers,198 1a,b), the results are difficult to extrapolate to mammalian neural cells. In the work reported here, when glucose was used, the affinity of the transporters at the outer face of the membrane [Km = 1.02 + 0.09 (6) mM] agreed well with that reported by several authors for dissociated brain cells and other purified preparations of neural cells in primary cultures (Roeder & Tildon, 1984;Roeder et al, 1985).…”

Section: Discussionsupporting

confidence: 79%

Glucose transporters in isolated chromaffin cells. Effects of insulin and secretagogues

Delicado¹,

Portugal²

1987

Biochemical Journal

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1. Isolated chromaffin cells from bovine adrenal medulla were used to study glucose transport in a homogeneous neural tissue. 2. The affinity of glucose transporters was 1.20 + 0.52 mm by the infinite-cis technique and 1.02 + 0.09 mm by the direct transport experiments. 3. The affinity for 2-deoxyglucose of these transporters was 2.3 mm. 4. The glucose transporters, quantified by [3H]cytochalasin B binding, were 419532 ±120740 receptors/cell, which corresponds to about 7.2 + 2 pmol/mg of protein, with KD = 0.1 /LM. 5. High-affinity insulin receptors with KD = 3.95 nM were present at a density of 68400 + 7500 per cell. 6. Insulin and secretagogues increased glucose transport, raising the transporter number at the plasma membrane without changes in the affinity.

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Section: Discussionsupporting

confidence: 79%

Glucose transporters in isolated chromaffin cells. Effects of insulin and secretagogues

Delicado¹,

Portugal²

1987

Biochemical Journal

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“…This is supported by the report by Vicario et al (3) suggesting that transport plays a major role in regulating lactate utilization by dissociated brain cells. A variety of preparations have been employed to study the uptake of substrates by brain cells, including isolated synaptosomes (27,28) enriched cell fractions (29), primary cultures of individual types of brain cells (30) and established cell lines (31,32). The present study used primary cultures of rat brain astrocytes to determine the role of transport in regulating the use of lactate by this cell type.…”

Section: Discussionmentioning

confidence: 99%

Transport ofl-lactate by cultured rat brain astrocytes

et al. 1993

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Several reports indicate that lactate can serve as an energy substrate for the brain. The rate of oxidation of this substrate by cultured rat brain astrocytes was 3-fold higher than the rate with glucose, suggesting that lactate can serve as an energy source for these cells. Since transport into the astrocytes may play an important role in regulating nutrient use by individuals types of brain cells, we investigated the uptake of L-[U-14C]lactate by primary cultures of rat brain astrocytes. Measurement of the net uptake suggested two carrier-mediated mechanisms and an Eadie-Hofstee type plot of the data supported this conclusion revealing 2 Km values of 0.49 and 11.38 mM and Vmax values of 16.55 and 173.84 nmol/min/mg protein, respectively. The rate of uptake was temperature dependent and was 3-fold higher at pH 6.2 than at 7.4, but was 50% less at pH 8.2. Although the lactate uptake carrier systems in astrocytes appeared to be labile when incubated in phosphate buffered saline for 20 minutes, the uptake process exhibited an accelerative exchange mechanism. In addition, lactate uptake was altered by several metabolic inhibitors and effectors. Potassium cyanide and alpha-cyano-4-hydroxycinnamate inhibited lactate uptake, but mersalyl had little or no effect. Phenylpyruvate, alpha-ketoisocaproate, and 3-hydroxybutyrate at 5 and 10 mM greatly attenuated the rate of lactate uptake. These results suggest that the availability of lactate as an energy source is regulated in part by a biphasic transport system in primary astrocytes.

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“…Surprisingly, this increased accumulation is not attributable to an increase in the rate of glycogen synthesis, which was found to be significantly lower compared with FA-deficient control astrocytes. The b-AR agonist ISP not only helps in the transportation of glucose into cells and the synthesis of glycogen (59,60) but also helps in the conversion of glycogen to glucose. In glioma cell lines, b-AR stimulation results in an increase in intracellular cAMP, which in turn induces a breakdown of glycogen (61).…”

Section: Discussionmentioning

confidence: 99%

Docosahexaenoic acid facilitates cell maturation and β-adrenergic transmission in astrocytes

Joardar

Sen

Das

2006

Journal of Lipid Research

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The effects of docosahexaenoic acid (DHA; 22:6 n-3), a major v-3 PUFA in the mammalian brain, on the structure and function of astrocytes were studied using primary cultures from rat cerebra. Gas-liquid chromatography of methyl esters of FAs isolated from cultures exposed to individual FAs, namely, stearic acid, linoleic acid, arachidonic acid, and DHA, showed alterations in the lipid profiles of the membranes, with a preferential incorporation of the FA to which the cells were exposed. Immunofluorescence studies demonstrated that unlike treatment with other FAs, after which the astrocytes remained as immature radial forms, DHA-treated astrocytes showed distinct differentiation, having morphology comparable to those grown in normal serum-containing medium. The long-chain FA docosahexaenoic acid (DHA; 22:6n-3) constitutes a large proportion of membrane phospholipids in the central nervous system and is particularly concentrated in the aminophospholipids phosphatidylethanolamine and phosphatidylserine of membranes. DHA can also be synthesized from the shorter chain precursor a-linolenic acid (18:3n-3), an essential FA that cannot be synthesized de novo by animal tissues and must be obtained from the diet (1). The importance of DHA in maintaining the structural and functional integrity of membranes is highlighted by the fact that it cannot be easily depleted from the brain (2). It is now well recognized that DHA is essential for normal brain development in animals and humans (3). In the human brain, the major accumulation occurs during the last period of gestation (4). DHA deficiency causes impairment of learning and memory. Supplementation of DHA reverses the effect by increasing the number of Fos-positive neurons and promoting neurite outgrowth and the size of the cell body in the CA1 hippocampus (5, 6) and restores long-term potentiation in aged rats (7,8). DHA plays a crucial role in membrane order (membrane fluidity), the regulation of phosphatidylserine levels (9), and the protection of neural cells from apoptotic death (10-12). Changes in energy metabolism induced by n-3 deficiency could result from functional alteration in glucose transporters (13).Although much of our understanding of the effect of DHA on the central nervous system has involved studies of neurons, existing knowledge regarding its effect on astrocytes is scarce. Astroglial cells constitute the major cells of the adult mammalian brain, outnumbering neurons by manyfold. Like neurons, astrocytes also undergo morphogenesis both in vivo (14) and in vitro (15,16) characterized by changes in cell shape. In addition to maintaining the microenvironment of neurons, astrocytes play a constitutive role in the formation of the bloodbrain barrier (17), represent the major glycogen depots of brain (18), support immune defense by producing various immunoactive cytokines (17), and maintain the external potassium concentration (19). Additionally, astrocytes possess myriad neurotransmitter receptors (20), most of which are transmembrane in nature and...

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Glucose Transport in Astrocytes: Regulation by Thyroid Hormone

Cited by 42 publications

References 43 publications

Glucose transporters in isolated chromaffin cells. Effects of insulin and secretagogues

Glucose transporters in isolated chromaffin cells. Effects of insulin and secretagogues

Transport ofl-lactate by cultured rat brain astrocytes

Docosahexaenoic acid facilitates cell maturation and β-adrenergic transmission in astrocytes

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