Departments of Psychiatry and Pharmacology, The Psychiatric Institute, The University of Illinois at Chicago, Chicago, Illinois 60612, USA.
J Neurochem. 2012 May;121(3):438-50. doi: 10.1111/j.1471-4159.2012.07695.x. Epub 2012 Mar 15.
In neurons exposed to glutamate, Ca²⁺ influx triggers intracellular Zn²⁺ release via an as yet unclear mechanism. As glutamate induces a Ca²⁺-dependent cytosolic acidification, the present work tested the relationships among intracellular Ca²⁺ concentration (Ca²⁺), intracellular pH (pH(i) ), and Zn²⁺. Cultured hippocampal neurons were exposed to glutamate and glycine (Glu/Gly), while Zn²⁺, Ca²⁺ and pH(i) were monitored using FluoZin-3, Fura2-FF, and 2',7'-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein, respectively. Glu/Gly applications decreased pH(i) to 6.1 and induced intracellular Zn²⁺ release in a Ca²⁺-dependent manner, as expected. The pH(i) drop reduced the affinity of FluoZin-3 and Fura-2-FF for Zn²⁺. The rate of Glu/Gly-induced Zn²⁺ increase was not correlated with the rate of Ca²⁺ increase. Instead, the extent of Zn²⁺ elevations corresponded well to the rate of pH(i) drop. Namely, Zn²⁺ increased more in more highly acidified neurons. Inhibiting the mechanisms responsible for the Ca²⁺-dependent pH(i) drop (plasmalemmal Ca²⁺ pump and mitochondria) counteracted the Glu/Gly-induced intracellular Zn²⁺ release. Alkaline pH (8.5) suppressed Glu/Gly-induced intracellular Zn²⁺ release whereas acidic pH (6.0) enhanced it. A pH(i) drop to 6.0 (without any Ca²⁺ influx or glutamate receptor activation) led to intracellular Zn²⁺ release; the released Zn²⁺ (free Zn²⁺ plus Zn²⁺) bound to Fura-2FF and FluoZin-3) reached 1 μM.
在暴露于谷氨酸的神经元中，Ca²⁺内流通过一个尚不清楚的机制触发细胞内 Zn²⁺释放。由于谷氨酸诱导 Ca²⁺依赖性胞质酸化，本研究测试了细胞内 Ca²⁺浓度 (Ca²⁺)、细胞内 pH 值 (pH(i)) 和 Zn²⁺ 之间的关系。培养的海马神经元暴露于谷氨酸和甘氨酸 (Glu/Gly) 中，同时使用 FluoZin-3、Fura2-FF 和 2',7'-双-(2-羧乙基)-5(6)-羧基荧光素分别监测 Zn²⁺、Ca²⁺ 和 pH(i)。如预期的那样，Glu/Gly 处理使 pH(i) 降低到 6.1，并以 Ca²⁺依赖性方式诱导细胞内 Zn²⁺释放。pH(i) 下降降低了 FluoZin-3 和 Fura-2-FF 与 Zn²⁺的亲和力。Glu/Gly 诱导的 Zn²⁺ 增加速率与 Ca²⁺ 增加速率无关。相反，Zn²⁺ 升高的程度与 pH(i) 下降的速率非常吻合。也就是说，在 pH(i) 下降幅度更大的神经元中，Zn²⁺ 增加更多。抑制负责 Ca²⁺依赖性 pH(i) 下降的机制（质膜 Ca²⁺泵和线粒体）抵消了 Glu/Gly 诱导的细胞内 Zn²⁺释放。碱性 pH（8.5）抑制 Glu/Gly 诱导的细胞内 Zn²⁺释放，而酸性 pH（6.0）增强其释放。pH(i) 下降到 6.0（没有任何 Ca²⁺内流或谷氨酸受体激活）导致细胞内 Zn²⁺释放；释放的 Zn²⁺（游离 Zn²⁺加 Zn²⁺）与 Fura-2FF 和 FluoZin-3 结合）达到 1 μM。
