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1.
Elevation of glutathione levels by ammonium ions in primary cultures of rat astrocytes 总被引:4,自引:0,他引:4
It is well established that ammonia is detoxified in the brain to form glutamine and that astrocytes play a major role in this process. The synthesis of glutamine requires glutamate and ATP. Since glutamate and ATP are also required for the synthesis of glutathione (GSH), we examined the effect of pathophysiological concentrations of ammonia on levels of GSH in primary cultures of astrocytes. GSH content in the medium increased in a dose- and time-dependent manner in the presence of ammonia. After an initial decrease, cellular GSH content increased in a similar manner. The levels of glutathione disulfide (GSSG) were also increased. A linear relationship was observed between ammonia concentration and the increase in GSH levels. An increase in the efflux of GSH from cells into medium was also observed under these conditions. Buthionine sulfoximine and acivicin, but not methionine sulfoximine, blocked the ammonia induced increase in GSH levels. No, or minor, changes in the activities of enzymes (gamma-glutamyl transpeptidase, GSH reductase and GSH-peroxidase) that might influence GSH levels were identified and thus could not account for the ammonia induced increase in GSH levels in astrocytes. These findings indicate that pathophysiological concentrations of ammonium ions result in increased astroglial levels of GSH which may affect the metabolism and function of astrocytes. 相似文献
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Sangman Lee 《Journal of Plant Biology》2005,48(1):57-63
Cysteine (Cys) represses the activity of several key regulatory enzymes in the plant sulfate assimilatory pathway. However,
it is not clear whether this effect arises from Cys itself or through its conversion to either sulfate or glutathione (GSH).
Therefore, we examined this phenomenon by analyzing the activity of adenosine-5′-phosphosulfate (APS) reductase. Both APS
reductase (AR) activity and mRNA levels were decreased by treatingArabidopsis thaliana roots with 1 mM Cys. The intracellular sulfate concentration was not affected, whereas enzymatic activity and, to some extent,
the mRNA level, declined. Cys treatment in sulfur-starved plants also diminished both parameters. However, this response to
Cys was more efficient than when plants were treated with an equal amount of sulfate. When Cys was removed from both Cys-and
sulfate-fed plants, AR activity was recovered; the same removal of sulfate was not so effective. Moreover, buthionine sulfoximine
(BSO), an inhibitor of GSH synthesis, did not influence the repression of AR by Cys. Finally the AR enzyme was inhibited by
cysteinein vitro. These results indicate that Cys represses AR by inhibiting mRNA expression and by directly repressing enzymatic activity,
rather than through its conversion to either sulfate or GSH. 相似文献
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Tian J Washizawa N Gu LH Levin MS Wang L Rubin DC Mwangi S Srinivasan S Gao Y Jones DP Ziegler TR 《American journal of physiology. Regulatory, integrative and comparative physiology》2007,292(3):R1081-R1091
Limited data in animal models suggest that colonic mucosa undergoes adaptive growth following massive small bowel resection (SBR). In vitro data suggest that intestinal cell growth is regulated by reactive oxygen species and redox couples [e.g., glutathione (GSH)/glutathione disulfide (GSSG) and cysteine (Cys)/cystine (CySS) redox]. We investigated the effects of SBR and alterations in redox on colonic growth indexes in rats after either small bowel transection (TX) or 80% midjejunoileal resection (RX). Rats were pair fed +/- blockade of endogenous GSH synthesis with buthionine sulfoximine (BSO). Indexes of colonic growth, proliferation, and apoptosis and GSH/GSSG and Cys/CySS redox potentials (E(h)) were determined. RX significantly increased colonic crypt depth, number of cells per crypt, and epithelial cell proliferation [crypt cell bromodeoxyuridine (BrdU) incorporation]. Administration of BSO markedly decreased colonic mucosal GSH, GSSG, and Cys concentrations in both TX and RX groups, with a resultant oxidation of GSH/GSSG and Cys/CySS E(h). BSO did not alter colonic crypt cell apoptosis but significantly increased all colonic mucosal growth indexes (crypt depth, cells/crypt, and BrdU incorporation) in both TX and RX groups in a time- and dose-dependent manner. BSO significantly decreased plasma GSH and GSSG, oxidized GSH/GSSG E(h), and increased plasma Cys and CySS concentrations. Collectively, these data provide in vivo evidence indicating that oxidized colonic mucosal redox status stimulates colonic mucosal growth in rats. The data also suggest that GSH is required to maintain normal colonic and plasma Cys/CySS homeostasis in these animal models. 相似文献
6.
Coordinated expression of sulfate uptake and components of the sulfate assimilatory pathway in maize 总被引:5,自引:0,他引:5
Hopkins L Parmar S Bouranis DL Howarth JR Hawkesford MJ 《Plant biology (Stuttgart, Germany)》2004,6(4):408-414
A high-affinity-type sulfate transporter (Group 1: ZmST1;1, Accession No. AF355602) has been cloned from maize seedlings by RT-PCR. Tissue and cell specific localisation of this sulfate transporter has been determined along the developmental gradient of the root and in leaves of different ages. In S-sufficient conditions there was uniform low expression of ZmST1;1 in the root and very low expression in the leaves. Increased mRNA abundance and sulfate influx capacity indicated that S-starvation increased ZmST1;1 expression in roots, especially at the top of the root (just behind the seed, the area possessing most laterals and root hairs) compared to the root tip. Similarly a group 2, probable low affinity-type sulfate transporter, ZmST2;1, and also ATP-sulfurylase and APS-reductase but not OAS(thiol)lyase were induced by S-starvation and showed highest expression in the upper section of the root. S-starvation increased root/shoot ratio by 20 % and increased root lateral length and abundance in the region closest to the root tip. As the increase in root proliferation was not as great as the increase in mRNA pools, it was clear that there was a higher cellular abundance of the mRNAs for sulfate transporters, ATP-sulfurylase, and APS-reductase in response to sulfur starvation. In the leaves, the sulfate transporters, ATP-sulfurylase and APS-reductase were induced by S-starvation with the most mature leaf showing increased mRNA abundance first. In situ hybridization indicated that ZmST1;1 was expressed in epidermal and endodermal cell layers throughout the root whilst OAS(thiol)lyase was highly expressed in the root cortex. 相似文献
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Inter-organ signaling in plants: regulation of ATP sulfurylase and sulfate transporter genes expression in roots mediated by phloem-translocated compound 总被引:11,自引:0,他引:11
Anne G. Lappartient J. John Vidmar Thomas Leustek Anthony D. M. Glass Bruno Touraine 《The Plant journal : for cell and molecular biology》1999,18(1):89-95
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Effect of short-term dark incubation with sulfate, chloride and selenate on the glutathione content of spinach leaf discs 总被引:3,自引:0,他引:3
A 24 h incubation of leaf discs of spinach ( Spinacia oleracea L. cv. Estivato) in darkness with 50 and 100 m M sulfate resulted in a two- to three-fold increase in the level of glutathione (GSH), a compound which may serve as storage of excess reduced sulfur in the plant. The accumulated GSH was a small fraction (around 1%) of the sulfate taken up in the spinach leaf discs. Incubation of spinach leaf discs with 50 and 100 m M chloride resulted in only a 30% increase of the water-soluble non-protein-SH; the uptake of electrolytes was comparable to that observed with sulfate. This indicated that the increase of the GSH level upon incubation with sulfate was rather specific and not due to salinity. Incubation with 50 m M Na2 SO4 did not affect water-soluble protein-SH content after 24 h. Addition of 1 and 10 m M selenate, an inhibitor of sulfate reduction, strongly reduced sulfate-induced GSH accumulation in spinach leaf discs, both in light and darkness. It was concluded that the sulfate-induced SH accumulation was due to a substantial de novo reduction of sulfate in darkness and subsequent incorporation of the reduced sulfur into GSH. The role of the sulfate concentration at the reaction site of ATP sulfurylase in the regulation of sulfur assimilation in the plant is discussed with respect to the low affinity of the enzyme for sulfate. 相似文献
9.
Ju-Sung Kim Sang-Gyu Seo Sun-Hyung Kim Kenji Usui Ie-Sung Shim 《Journal of Plant Biology》2005,48(4):404-410
We examined the effects of the constituent amino acids for glutathione (GSH) — glutamate (Glu), cysteine (Cys), and glycine
(Gly) — on GSH synthesis in Chinese cabbage seedlings. Glu, Cys, and Gly were applied simultaneously (100 mg L-1) to the culture solution for 2 d. When compared with the control, GSH concentrations were increased by 2.1-fold (640.4 nmol
g-1 FW) and 1.5-fold (416.4 nmol g-1 FW) in the first leaf and the roots, respectively. Of all the free amino acids, the non-essentials, including Glu, Cys and
Gly, occupied 95.5% (shoots) and 81.9% (roots) of the total. Cys supplements greatly enhanced the GSH concentration in the
roots; application of 100 mg L-1 increased the level by 7-fold over the control. The activity of GSH synthetase was higher in the roots than in the leaf,
whereas that of y-glutamylcysteine synthetase was higher in the leaf. 相似文献
10.
Heiss Senta Schäfer Holger J. Haag-Kerwer Angela Rausch Thomas 《Plant molecular biology》1999,39(4):847-857