Ascorbic acid transport in mouse and rat astrocytes is reversibly inhibited by furosemide, SITS, and DIDS

Jx, Wilson; Dixon, S. Jeffrey

doi:10.1007/bf00965504

Cited by 28 publications

(15 citation statements)

References 42 publications

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“…This does not completely rule out the possibility that the cells accumulated DHA and then reduced it to ascorbate, but it indicates that the pig coronary artery smooth muscle cells were capable of retaining 14 C-ascorbate. The rate of ascorbate accumulation by cells incubated in medium containing 10 µ M ascorbate was 1,183 ± 148 nmol/g of protein/12 min or 99 ± 12 nmol/g of protein/min for smooth muscle cells, which was considerably higher than the value of 13 nmol/g of protein/min reported previously for bovine pulmonary arterial endothelial cells [35]. Human umbilical vein smooth muscle cells have recently been reported to take up ascorbate or DHA.…”

Section: Discussioncontrasting

confidence: 40%

Ascorbate Transport in Pig Coronary Artery Smooth Muscle: Na<sup>+</sup> Removal and Oxidative Stress Increase Loss of Accumulated Cellular Ascorbate

et al. 2000

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Pig deendothelialized coronary artery rings and smooth muscle cells cultured from them accumulated ascorbate from medium containing Na⁺. The accumulated material was determined to be ascorbate using high-performance liquid chromatography. We further characterized ascorbate uptake in the cultured cells. The data fitted best with a Hill coefficient of 1 for ascorbate (K_asc = 22 ± 2 μM) and 2 for Na⁺ (K_Na = 84 ± 10 mM). The anion transport inhibitors sulfinpyrazone and 4,4′-diisothiocyanatostilbene-2,2′-disulfonate (DIDS) inhibited the uptake. Transferring cultured cells loaded with ¹⁴C-ascorbate into an ascorbate-free solution resulted in a biphasic loss of radioactivity – an initial sulfinpyrazone-insensitive faster phase and a late sulfinpyrazone-sensitive slower phase. Transferring loaded cells into a Na⁺-free medium increased the loss in the initial phase in a sulfinpyrazone-sensitive manner, suggesting that the ascorbate transporter is bidirectional. Including peroxide or superoxide in the solution increased the loss of radioactivity. Thus, ascorbate accumulated in coronary artery smooth muscle cells by a Na⁺-dependent transporter was lost in an ascorbate-free solution, and the loss was increased by removing Na⁺ from the medium or by oxidative stress.

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Section: Discussioncontrasting

confidence: 40%

Ascorbate Transport in Pig Coronary Artery Smooth Muscle: Na<sup>+</sup> Removal and Oxidative Stress Increase Loss of Accumulated Cellular Ascorbate

et al. 2000

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“…Primary astrocyte cultures were prepared from newborn rats at postnatal day 1 (P1) (Wilson and Dixon, 1989). The upper portion of the skull was removed and the meninges carefully dissected away to avoid contamination of the culture with fibroblasts.…”

Section: Primary Cell Culturementioning

confidence: 99%

Transcriptional regulation of scar gene expression in primary astrocytes

Gris

Tighe

Levin

et al. 2007

Glia

115

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The failure of the adult injured spinal cord to support axonal regeneration is in part attributed to the glial scar. Reactive astrocytes constitute a major cellular component of the glial scar and are heterogeneous with respect to the extracellular matrix proteins that they secrete. Astrocytes may produce antiregenerative molecules such as chondroitin sulphate proteoglycans (CSPGs) or proregenerative molecules such as laminin and fibronectin. While many different CSPGs are expressed after spinal cord injury (SCI) they all rely on the same enzymes, xylosyltransferase-I and -II (XT-I, XT-II) and chondroitin 4-sulfotransferase (C4ST) to add the repulsive chondroitin sulfate side chains to their core proteins. We show that XT-I, XT-II, and C4ST are part of a CSPG biosynthetic gene (CBG) battery. Using primary astrocyte cultures and quantitative PCR we demonstrate that TGFbeta2, PDGF, and IL-6 induce the expression of CBGs, laminin and fibronectin by several-fold. We further show that over-expression of the transcription factor SOX9 also strongly induces the expression of CBGs but does not increase the expression of laminin or fibronectin. Correspondingly, SOX9 knock-down in primary astrocytes causes a decrease in CBG and an increase in laminin and fibronectin mRNA levels. Finally, we show that the in vivo expression profiles of TGFbeta2, PDGF, IL-6, and SOX9 are consistent with their potential roles in differentially regulating CBGs, laminin and fibronectin gene expression in the injured spinal cord. This work suggests that SOX9 levels may be pivotal in determining the balance of pro- and anti-regenerative extracellular matrix molecules produced by astrocytes.

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“…Concentrative uptake of ascorbate into astrocytes is mediated by a high-affinity sodiumascorbate cotransporter located in the astrocytic plasma membrane (Fig. 2) (Wilson 1989;Wilson and Dixon 1989;Siushansian and Wilson 1995). This is a secondary active transport system driven by the transmembrane sodium gradient and membrane potential.…”

Section: Distribution Of Antioxidants In Brain Cell Typesmentioning

confidence: 99%

Antioxidant defense of the brain: a role for astrocytes

Wilson¹

1997

Can. J. Physiol. Pharmacol.

359

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Partially reduced forms of oxygen are produced in the brain during cellular respiration and, at accelerated rates, during brain insults. The most reactive forms, such as the hydroxyl radical, are capable of oxidizing proteins, lipids, and nucleic acids. Oxidative injury has been implicated in degenerative diseases, epilepsy, trauma, and stroke. It is a threshold phenomenon that occurs after antioxidant mechanisms are overwhelmed. Oxidative stress is a disparity between the rates of free radical production and elimination. This imbalance is initiated by numerous factors: acidosis; transition metals; amyloid beta-peptide; the neurotransmitters dopamine, glutamate, and nitric oxide; and uncouplers of mitochondrial electron transport. Antioxidant defenses include the enzymes superoxide dismutase, glutathione peroxidase, and catalase, as well as the low molecular weight reductants alpha-tocopherol (vitamin E), glutathione, and ascorbate (reduced vitamin C). Astrocytes maintain high intracellular concentrations of certain antioxidants, making these cells resistant to oxidative stress relative to oligodendrocytes and neurons. Following reactive gliosis, the neuroprotective role of astrocytes may be accentuated because of increases in a number of activities: expression of antioxidant enzymes; transport and metabolism of glucose that yields reducing equivalents for antioxidant regeneration and lactate for neuronal metabolism; synthesis of glutathione; and recycling of vitamin C. In the latter process, astrocytes take up oxidized vitamin C (dehydroascorbic acid, DHAA) through plasma membrane transporters, reduce it to ascorbate, and then release ascorbate to the extracellular fluid, where it may contribute to antioxidant defense of neurons.

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Ascorbic acid transport in mouse and rat astrocytes is reversibly inhibited by furosemide, SITS, and DIDS

Cited by 28 publications

References 42 publications

Ascorbate Transport in Pig Coronary Artery Smooth Muscle: Na<sup>+</sup> Removal and Oxidative Stress Increase Loss of Accumulated Cellular Ascorbate

Ascorbate Transport in Pig Coronary Artery Smooth Muscle: Na<sup>+</sup> Removal and Oxidative Stress Increase Loss of Accumulated Cellular Ascorbate

Transcriptional regulation of scar gene expression in primary astrocytes

Antioxidant defense of the brain: a role for astrocytes

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