Raley-Susman K M, Sapolsky R M, Kopito R R
Department of Biology, Vassar College, Poughkeepsie, NY 12601.
Brain Res. 1993 Jun 18;614(1-2):308-14. doi: 10.1016/0006-8993(93)91049-x.
We studied Cl-/HCO3- exchange function in acutely dissociated single hippocampal neurons from adult and fetal day 18 rat using a fluorescent intracellular pH (pHi) indicator dye. The presence of Cl-/HCO3- exchange activity was assayed by observing the elevation in pHi upon acute reversal of the Cl- gradient. Resting intracellular pH in acutely dissociated neurons of both adult and fetal tissue was significantly higher than that of cultured fetal hippocampal neurons (day 10-12 in culture). Acute removal of extracellular Cl- caused a rapid and reversible increase in pHi by 0.25 pH units in adult neurons but had virtually no effect in similarly dissociated fetal neurons. Cl-/HCO3- exchange activity was also undetectable in fetal cultured hippocampal neurons. The mRNA for the anion exchanger AE3 is expressed abundantly in adult rodent neurons. AE3 is a potential candidate molecule for the observed Cl-/HCO3- exchange activity. In situ hybridization was used to monitor expression of the AE3 gene in these two age groups. We found that both adult and fetal neurons express AE3 mRNA. These results indicate that AE3 may not function as a Cl-/HCO3- exchanger in fetal neurons, in contrast to its possible role in the adult brain.
我们使用一种荧光细胞内pH（pHi）指示剂染料，研究了成年大鼠和胚胎第18天大鼠急性分离的单个海马神经元中的Cl⁻/HCO₃⁻交换功能。通过观察Cl⁻梯度急性反转时pHi的升高来检测Cl⁻/HCO₃⁻交换活性的存在。成年和胚胎组织急性分离神经元的静息细胞内pH均显著高于培养的胚胎海马神经元（培养10 - 12天）。急性去除细胞外Cl⁻导致成年神经元的pHi迅速且可逆地升高0.25个pH单位，但对类似分离的胚胎神经元几乎没有影响。在培养的胚胎海马神经元中也未检测到Cl⁻/HCO₃⁻交换活性。阴离子交换蛋白AE3的mRNA在成年啮齿动物神经元中大量表达。AE3是观察到的Cl⁻/HCO₃⁻交换活性的潜在候选分子。原位杂交用于监测这两个年龄组中AE3基因的表达。我们发现成年和胚胎神经元均表达AE3 mRNA。这些结果表明，与AE3在成体大脑中可能的作用相反，它在胚胎神经元中可能不作为Cl⁻/HCO₃⁻交换体发挥作用。
