Swanson R A, Graham S H
Department of Neurology, University of California, San Francisco.
Brain Res. 1994 Nov 21;664(1-2):94-100. doi: 10.1016/0006-8993(94)91958-5.
The Krebs cycle inhibitor fluorocitrate (FC) and its precursor fluoroacetate (FA) are taken up in brain preferentially by glia. These compounds are used experimentally to inhibit glial metabolism in situ. The actions of these agents have been attributed to both the disruption of carbon flux through the Krebs cycle and to impairment of ATP production. We used primary astrocyte cultures to evaluate these two possible modes of action. Astrocyte ATP levels exhibited little or no reduction during incubation with 0.5 mM FC or 25 mM FA. Correspondingly, FC and FA caused less than 30% reductions in glutamate uptake (P > 0.05), an important energy-dependent astrocyte function. Carbon flux through the Krebs cycle was assessed by measuring astrocyte glutamine production in the absence of exogenous glutamate or aspartate. Under these conditions, glutamine production was reduced 65 +/- 5% by 0.5 mM FC and 61 +/- 3% by 25 mM FA (P < 0.01). In contrast, FC and FA had no effect on glutamine production when 50 microM glutamate was provided in the media. These findings suggest that the metabolic effects of FC and FA on astrocytes in vivo result from impairment of carbon flux through the Krebs cycle, and not from impairment of oxidative ATP production.
三羧酸循环抑制剂氟柠檬酸（FC）及其前体氟乙酸（FA）在大脑中优先被神经胶质细胞摄取。这些化合物在实验中用于原位抑制神经胶质细胞的代谢。这些药物的作用归因于三羧酸循环中碳通量的破坏以及ATP生成的受损。我们使用原代星形胶质细胞培养物来评估这两种可能的作用方式。在与0.5 mM FC或25 mM FA孵育期间，星形胶质细胞的ATP水平几乎没有降低或没有降低。相应地，FC和FA使谷氨酸摄取减少不到30%（P>0.05），谷氨酸摄取是一种重要的能量依赖型星形胶质细胞功能。通过在没有外源性谷氨酸或天冬氨酸的情况下测量星形胶质细胞谷氨酰胺的产生来评估三羧酸循环中的碳通量。在这些条件下，0.5 mM FC使谷氨酰胺产生减少65±5%，25 mM FA使谷氨酰胺产生减少61±3%（P<0.01）。相反，当培养基中提供50μM谷氨酸时，FC和FA对谷氨酰胺产生没有影响。这些发现表明，FC和FA对体内星形胶质细胞的代谢作用是由于三羧酸循环中碳通量的受损，而不是由于氧化ATP生成的受损。
