Braun N, Zhu Y, Krieglstein J, Culmsee C, Zimmermann H
Biozentrum der J.W. Goethe-Universität, AK Neurochemie, D-60439 Frankfurt am Main, Germany.
J Neurosci. 1998 Jul 1;18(13):4891-900. doi: 10.1523/JNEUROSCI.18-13-04891.1998.
A short ischemic period induced by the transient occlusion of major brain arteries induces neuronal damage in selectively vulnerable regions of the hippocampus. Adenosine is considered to be one of the major neuroprotective substances produced in the ischemic brain. It can be released from damaged cells, but it also could be generated extracellularly from released ATP via a surface-located enzyme chain. Using the rat model of global forebrain ischemia, we applied a short (10 min) transient interruption of blood flow and studied the distribution of ectonucleotidase activities in the hippocampus. Northern hybridization of mRNA isolated from hippocampi of sham-operated and ischemic animals revealed an upregulation of ectoapyrase (capable of hydrolyzing nucleoside 5'-tri- and diphosphates) and ecto-5'-nucleotidase (capable of hydrolyzing nucleoside 5'-monophosphates). A histochemical analysis that used ATP, UTP, ADP, or AMP as substrates revealed a strong and selective increase in enzyme activity in the injured areas of the hippocampus. Enhanced staining could be observed first at 2 d. Staining increased within the next days and persisted at 28 d after ischemia. The spatiotemporal development of catalytic activities was identical for all substrates. It was most pronounced in the CA1 subfield and also could be detected in the dentate hilus and to a marginal extent in CA3. The histochemical staining corresponded closely to the development of markers for reactive glia, in particular of microglia. The upregulation of ectonucleotidase activities implies increased nucleotide release from the damaged tissue and could play a role in the postischemic control of nucleotide-mediated cellular responses.
大脑主要动脉的短暂闭塞所引发的短暂缺血期，会在海马体的选择性易损区域诱发神经元损伤。腺苷被认为是缺血性脑内产生的主要神经保护物质之一。它可从受损细胞释放，但也能通过位于表面的酶链由释放的ATP在细胞外生成。利用全脑缺血的大鼠模型，我们进行了短暂（10分钟）的血流中断，并研究了海马体中外核苷酸酶活性的分布。对假手术动物和缺血动物海马体分离出的mRNA进行Northern杂交分析，结果显示外切焦磷酸酶（能够水解核苷5'-三磷酸和二磷酸）和外切5'-核苷酸酶（能够水解核苷5'-单磷酸）上调。一项以ATP、UTP、ADP或AMP为底物的组织化学分析显示，海马体损伤区域的酶活性有强烈且选择性的增加。增强染色最早在第2天可观察到。在接下来的几天内染色增加，并在缺血后28天持续存在。所有底物催化活性的时空发展情况相同。在CA1亚区最为明显，在齿状回门也可检测到，在CA3区有轻微表现。组织化学染色与反应性胶质细胞，尤其是小胶质细胞标志物的发展密切相关。外核苷酸酶活性的上调意味着受损组织中核苷酸释放增加，可能在缺血后对核苷酸介导的细胞反应的控制中发挥作用。
