Marlier L N, Zheng T, Tang J, Grayson D R
Fidia-Georgetown Institute for the Neurosciences, Georgetown University, Washington, DC 20007.
Brain Res Mol Brain Res. 1993 Oct;20(1-2):21-39. doi: 10.1016/0169-328x(93)90107-z.
The cardiac Na+/Ca2+ exchanger is a bidirectional electrogenic ion transporter that exchanges three Na+ ions for each Ca2+ ion and plays a critical role in returning sarcolemma Ca2+ concentrations to their resting levels. Because of the importance that the Na+/Ca2+ exchanger may play in maintaining neuronal Ca2+ homeostasis in the central nervous system, we subcloned a 456 bp portion of the Na+/Ca2+ exchanger cDNA from RNA isolated from primary cultures of rat cerebellar granule neurons using the polymerase chain reaction (PCR). This cDNA fragment was sequenced and shown to share 91.4% sequence identity with the human and 88% sequence identity with the canine cardiac Na+/Ca2+ exchangers. The PCR amplification product was used to analyze the distribution of this portion of the Na+/Ca2+ exchanger mRNA in various regions of the CNS by both Northern blotting and in situ hybridization histochemistry. The Northern analysis showed that the rank order of abundance of this mRNA was: hippocampus > cortex > cerebellum > hypothalamus > midbrain > striatum. The in situ hybridization data indicated that the corresponding mRNA containing this portion of the exchanger was present in numerous brain regions including multiple cortical layers, the hippocampus, septal nuclei, various thalamic nuclei, cerebellum, hypothalamus, olfactory bulb, brainstem, in various regions of the thoracic spinal cord and to a lesser extent in the striatum. The differential distribution of the mRNA as revealed by the in situ hybridization pattern suggests that either additional molecular variants exist or that different Na+/Ca2+ exchange mechanisms may be operative in those cell types that contain low amounts of this fragment of the exchanger mRNA.
心脏钠钙交换体是一种双向生电离子转运体，每交换一个钙离子就转运三个钠离子，在将肌膜钙离子浓度恢复到静息水平方面发挥着关键作用。由于钠钙交换体在维持中枢神经系统神经元钙稳态中可能具有重要作用，我们利用聚合酶链反应（PCR）从大鼠小脑颗粒神经元原代培养物分离的RNA中克隆了钠钙交换体cDNA的一个456bp片段。对该cDNA片段进行测序后发现，它与人类心脏钠钙交换体的序列同一性为91.4%，与犬类心脏钠钙交换体的序列同一性为88%。PCR扩增产物用于通过Northern印迹法和原位杂交组织化学分析钠钙交换体mRNA这一部分在中枢神经系统各个区域的分布。Northern分析表明，该mRNA丰度的排序为：海马体＞皮质＞小脑＞下丘脑＞中脑＞纹状体。原位杂交数据表明，包含该交换体这一部分的相应mRNA存在于许多脑区，包括多个皮质层、海马体、隔核、各种丘脑核、小脑、下丘脑、嗅球、脑干、胸段脊髓的各个区域，在纹状体中的含量较少。原位杂交模式显示的mRNA差异分布表明，要么存在其他分子变体，要么在那些含有少量该交换体mRNA片段的细胞类型中可能存在不同的钠钙交换机制。
