Effects of Hypoxia, Glucose Deprivation and Recovery on the Expression of Nucleoside Transporters and Adenosine Uptake in Primary Culture of Rat Cortical Astrocytes

The aim of this study was to explore effects of hypoxia, glucose deprivation (HGD) and recovery on expression and activities of equilibrative nucleoside transporters (rENT) and concentrative nucleoside transporters (rCNT) in rat astrocytes in primary culture. Amounts of cellular ATP in the control group (CG, 5% CO2 in air, medium containing 7 mM D-glucose, 1 mM Na+-pyruvate, 1 h), HGD group (2% O-2/5% CO2 in N-2, pyruvate-free medium containing 1.5 mM D-glucose and 10 mM 2-deoxy-D-glucose, 1 h) and recovery group (RG, HGD for 1 h, followed by 1 h exposure to the same conditions as the CG) were (nmol/mg protein, n = 4) 18 +/- 1.6, 4.9 +/- 0.6 and 10.1 +/- 0.8, respectively. Extracellular adenosine concentrations increased from (nM, n = 3) 42 +/- 4 in the CG, to 99 +/- 8 in the HGD group and 86 +/- 3 in the RG. Real-time PCR and immunoblotting revealed that in the HGD group and RG, the amounts of rENT1 mRNA and protein were reduced to 40 and 50%, when compared to the CG, respectively. Astrocyte cultures took up [H-3] adenosine by concentrative and equilibrative transport processes; however, rENT1-mediated uptake was absent in the RG and cultures from the RG took up significantly less [H-3] adenosine by equilibrative mechanisms than cultures from the CG.