AIMTo explore the effects of hypoxia on expression of inducible nitric oxide synthase (iNOS) mRNA in cultured rat astrocytes.

METHODSCultured rat astrocytes were randomly divided into 4 groups: glutamate group (G), hypoxic group (H), hypoxia + glutamate group (H + G) and the control (C). Cells of control group were exposed to normoxic (95% air, 5% CO2) condition, and cells of G and H + G were incubated with 100 micromol/L L-glutamate, cells of H and H + G exposed to hypoxic conditions (5% CO2, 95% N2) at 37 degrees C. Each group had five timepoints which included 0 h, 3 h, 6 h, 12 h, 24 h, respectively. Expression of mRNAs of iNOS were detected with reverse transcription polymerase chain reaction (RT-PCR).

RESULTSExpression of iNOS mRNA was not detectable in G and C, while it increased dramatically and continuously from 6 h to 24 h in H and G + H. Expression of iNOS mRNA was significantly higher in H than both in G and C at 6 h, 12 h and 24 h, and expression of iNOS mRNA was the highest of all groups in G + H.

CONCLUSIONHypoxia upregulates the expression of iNOS mRNA in cultured astrocytes. Glutamate does not induce the expression of iNOS mRNA but enhance the effect of hypoxia, which is maybe one of the adaptive mechanisms of hypoxia-induced cerebral dilation.