Tholey et al. reported a decrease in GS activity in APC after 9h hypoxia at day 10 and 14 in culture, while at day 5 the GS activity remained unchanged under hypoxia. However, the hypoxic conditions used in the cited study can be described as anoxic rather than hypoxic, which is likely to severely affect the survival and Glu-metabolizing function of astrocytes. Twenty four hours under such condition resulted in total detachment and death of astroglial culture. It can be assumed that Gluuptake and metabolism of astrocytes depends not only on age but also on severity and duration of oxygen deprivation. This notion is supported by the work of Sher and Hu, who see no changes in GS-activity in 12-day old brain primary cultures containing neurons and astroglia upon moderate hypoxia without Glu for 24 h, while under 48h of hypoxia the GS-activity level was even increased. Under hypoxia, EPO increased the enzymatic activity of GS in aged glutamate-treated astrocytes. This may be due to a reduction by EPO of the factor detrimental to GS activity, oxidative stress. It is known that GS is a particularly vulnerable target for oxidation in the CNS, and that EPO can reduce oxidative stress in the brain. In accordance with other reports, in our study the enzymatic activity of GS was upregulated during simultaneous exposure of APC to hypoxia and Glu with increasing time in culture. On the other hand, as evidenced by Western blot analysis, the GS protein level in aged astrocytes decreased. Such complicity in GS regulation we came across also in our previous study performed on GFAP-positive keratinocytes of the skin, i.e. exposure of primary keratinocyte cultures or cell lines to ammonium ions resulted in enhanced enzymatic activity of GS, but not GS protein expression. Glutamate uptake by astrocytes is fundamentally important in the regulation of CNS function. Disruption of uptake can lead to excitotoxicity and is implicated in various neurodegenerative processes. Consistent with the findings of Dallas et al., in our study the Glu uptake under HC was decreased in aged cells. As shown here the capacity of culture-aged astrocytes for glutamate uptake was significantly decreased under HC, and it was slightly impaired even under NC in comparison with young cultures. The compromised adaptation of Glu-uptake by aged astrocytes may serve as an additional marker of their senescence. Various stress Dexrazoxane hydrochloride factors were shown to induce the senescent phenotype of astroglial in culture. Inflammation reflected by release of inflammatory interleukins and chemokines including IL-1�� and monocyte chemoattractant protein-1 is the one of these factors. Since hypoxia induces the production of IL-1�� and MCP1 in astrocytes it can be assumed that oxygen deprivation serves as a factor triggering the senescent pehotype of astrocytes. Though EPO at both concentrations increased the Glu uptake in intermediate and mature stage of astrocytes, its strongest effect occurred in aged astrocytes and using 5U/ml EPO. The efficiency of EPO at concentration of 5U/ml seems to be not a random phenomenon. This concentration of the EPO was measured in cerebrospinal fluid of stroke patients after intravenous administration of 33,000 IE of human recombinant erythropoietin resulting in significant improvement of clinical outcome and neurological recovery. At concentration of 5 U/day EPO was shown to induce the formation of synapses within different brain layers of gerbils and it protected primary cultured hippocampal and cerebral cortical neurons from NMDA receptor-mediated glutamate toxicity. LOUREIRIN-B Malfunction of astrocytic Glu transporters will lead to an excessively high extracellular Glu concentration which may result in neurodegeneration caused by the excitotoxic action of glutamate.