Multiple pathways of Pb2+ permeation in rat cerebellar granule neurones
Multiple pathways of Pb2+ permeation in rat cerebellar granule neurones
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DOI：
10.1046/j.1471-4159.2001.00557.x
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发表时间：
2001-10
影响因子：
4.7
通讯作者：
M. Mazzolini;S. Traverso;C. Marchetti
中科院分区：
文献类型：
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作者：
M. Mazzolini;S. Traverso;C. Marchetti
在来自8日龄大鼠的负载fura-2的小脑颗粒细胞中研究了铅（Pb 2+）摄取的途径。在标称无钙外部浴中，Pb 2+（5-50 µm）确定了荧光发射比（R = E340/E380）的增加，即使在没有任何特定刺激的情况下。这种升高具有剂量依赖性，不受mm Mg 2+或Ca 2+的显著影响，但它很容易被膜渗透性重金属螯合剂四（2-吡啶基甲基）乙二胺（TPEN，100 µm）逆转，表明这是由于Pb 2+流入。通过去极化高KCl溶液，上升速率dR/dt增加至5倍，表明通过电压依赖性通道的相当大的渗透。这种作用既不被尼莫地平拮抗，也不被BayK 8644增强，但它被ω-agatoxin IVA（200 nm）减弱，表明非L-型钙通道参与。在存在10-30 µm甘氨酸的情况下，谷氨酸或NMDA也可刺激Pb 2+内流，但仅在无镁溶液中，这表明NMDA型谷氨酸通道是Pb 2+摄取的另一条途径。Pb 2+引起染料的时间、剂量和刺激依赖性饱和，其细胞内浓度为10 µm，表明细胞内Pb 2+可以容易地达到微摩尔范围内的浓度。这些结果表明，神经元对Pb 2+中毒的特殊脆弱性与特定转运系统的存在有关，该系统介导Pb 2+快速摄取到神经元中。
The pathways of lead (Pb2+) uptake were studied in fura‐2‐loaded cerebellar granule cells from 8‐day‐old rats. In a nominal Ca‐free external bath, Pb2+ (5–50 µm) determined an increase of the fluorescence emission ratio (R = E340/E380) even in the absence of any specific stimulus. This rise was dose‐dependent, was not significantly affected by mm Mg2+ or Ca2+, but it was readily reversed by the membrane‐permeant heavy metal chelator tetrakis(2‐pyridylmethyl) ethylene‐diamine (TPEN, 100 µm), indicating that it was due to Pb2+ influx. The rate of rise, dR/dt, was increased up to a factor of 5 by depolarizing high‐KCl solution, indicating a sizeable permeation through voltage‐dependent channels. This effect was neither antagonized by nimodipine, nor enhanced by BayK8644, but it was slackened by ω‐agatoxin IVA (200 nm), suggesting an involvement of non‐L‐type calcium channels. Pb2+ influx was also stimulated by glutamic acid or NMDA in the presence of 10–30 µm glycine, but only in Mg‐free solution, suggesting that glutamate channels of the NMDA type are an additional pathway of Pb2+ uptake. Pb2+ caused a time‐, dose‐ and stimulus‐dependent saturation of the dye, whose intracellular concentration is ∼ 10 µm, indicating that intracellular Pb2+ can readily reach a concentration in the micromolar range. These results indicate that the particular vulnerability of neurones to Pb2+ poisoning is linked to the presence of specific transport systems, which mediate the rapid uptake of Pb2+ into the neurone.