Thoren Anna E, Helps Stephen C, Nilsson Michael, Sims Neil R
Centre for Neuroscience and Department of Medical Biochemistry, School of Medicine, Flinders University, Adelaide, Australia.
J Cereb Blood Flow Metab. 2005 Apr;25(4):440-50. doi: 10.1038/sj.jcbfm.9600035.
Astrocytes play many roles essential for normal brain activity. The ability of these cells to recover after temporary focal cerebral ischemia is likely to be one important determinant of the extent of brain dysfunction and tissue damage. We have assessed astrocytic function based on the incorporation of radiolabel from 1-14C-acetate into glutamine at 1 hour of recirculation after middle cerebral artery occlusion for 2 or 3 hours in rats. There were marked differences in the response between subregions within the tissue subjected to ischemia, but the overall pattern of changes was similar after each ischemic period. The striatum, which forms part of the severely ischemic focal tissue during arterial occlusion, showed a large (44% to 68%) decrease in glutamine labeling compared with equivalent tissue from the contralateral hemisphere. In contrast, 14C-glutamine content was not significantly altered in perifocal tissue in the cerebral cortex, which was subjected to more moderate ischemia. Cortical focal tissue also was not significantly affected, but the response was much more variable between rats. In these brain subregions, the extent of recovery of the 14C-acetate metabolism after ischemia was not a good predictor of the likelihood of subsequent infarct development. Interestingly, a similar pattern of responses persisted when recirculation was extended to 4 hours. These results indicate that many astrocytes, particularly in the cortex, remain viable and capable of at least some complex oxidative metabolism during the first few hours of recirculation.
星形胶质细胞对正常脑活动起着许多至关重要的作用。这些细胞在短暂性局灶性脑缺血后恢复的能力很可能是脑功能障碍和组织损伤程度的一个重要决定因素。我们在大鼠大脑中动脉闭塞2或3小时后再灌注1小时时，基于将放射性标记从1-¹⁴C-乙酸掺入谷氨酰胺来评估星形胶质细胞的功能。在遭受缺血的组织内各亚区域之间的反应存在显著差异，但在每个缺血期后变化的总体模式相似。纹状体在动脉闭塞期间形成严重缺血性局灶组织的一部分，与对侧半球的同等组织相比，其谷氨酰胺标记显示大幅（44%至68%）下降。相比之下，大脑皮层中遭受较中度缺血的灶周组织中¹⁴C-谷氨酰胺含量没有显著改变。皮层局灶组织也未受到显著影响，但不同大鼠之间的反应差异更大。在这些脑亚区域中，缺血后¹⁴C-乙酸代谢的恢复程度并不是后续梗死发展可能性的良好预测指标。有趣的是，当再灌注延长至4小时时，类似的反应模式仍然存在。这些结果表明，许多星形胶质细胞，尤其是皮层中的星形胶质细胞，在再灌注的最初几个小时内仍保持存活并能够进行至少一些复杂的氧化代谢。
