Cadmium uptake and toxicity via voltage-sensitive calcium channels.
Cadmium uptake and toxicity via voltage-sensitive calcium channels.
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DOI：
10.1016/s0021-9258(18)49259-9
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发表时间：
1987-12
期刊：
影响因子：
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通讯作者：
Patricia;Hinkle;Kinsella;K. Osterhoudt
中科院分区：
文献类型：
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作者：
Patricia;Hinkle;Kinsella;K. Osterhoudt
镉是一种剧毒的金属离子，细胞吸收镉的机制尚不清楚。我们研究了已建立的分泌细胞系GH4C1对镉的吸收和毒性，该细胞系具有很好的钙通道特征。尼莫地平是一种电压敏感钙通道拮抗剂，通过将CdCl2的LD50从15微米增加到45微米来保护细胞免受镉毒性，而钙通道激动剂BAY K8644则降低了LD50。三种类型的有机钙通道阻滞剂保护细胞免受镉毒性，其浓度先前被证明可以阻断高K+诱导的45Ca2+内流和分泌。20 μ m硝苯地平、4 μ m维拉帕米和7 μ m地尔硫卓的保护作用达到半最大。将细胞外钙浓度从20微米增加到10毫米也可以使CdCl2的LD50增加5倍，从而保护细胞免受镉的侵害。钙通道拮抗剂尼莫地平和激动剂BAY K8644都没有改变细胞内金属硫蛋白的浓度，而镉在18小时内导致金属硫蛋白增加9-20倍。镉是去极化刺激的45Ca2+摄取的有效阻断剂（IC50 = 4微米），用109Cd2+测量的镉的净摄入量小于钙的0.3%。虽然镉的吸收速率相对于钙的吸收速率较低，但通过电压敏感的钙通道进入似乎占镉吸收的很大一部分；高K+/BAY的K8644使30min时的cd2 +摄取增加57%，有利于通过通道进入。此外，100 nM尼莫地平阻断钙通道24 h后，细胞总109Cd2+积累减少63%。这些数据表明，镉通过二氢吡啶敏感、电压敏感的钙通道的通量是GH4C1细胞摄取镉的主要机制，并且药物阻断钙通道可以对镉毒性提供显着的保护。
The mechanism of cellular uptake of cadmium, a highly toxic metal ion, is not known. We have studied cadmium uptake and toxicity in an established secretory cell line, GH4C1, which has well characterized calcium channels. Nimodipine, an antagonist of voltage-sensitive calcium channels, protected cells against cadmium toxicity by increasing the LD50 for CdCl2 from 15 to 45 microM, whereas the calcium channel agonist BAY K8644 decreased the LD50. Organic calcium channel blockers of three classes protected cells from cadmium toxicity at concentrations previously shown to block high K+-induced 45Ca2+ influx and secretion. Half-maximal protective effects were obtained at 20 nM nifedipine, 4 microM verapamil, and 7 microM diltiazem. Increasing the extracellular calcium concentration from 20 microM to 10 mM also protected cells from cadmium by causing a 5-fold increase in the LD50 for CdCl2. Neither the calcium channel antagonist nimodipine nor the agonist BAY K8644 altered intracellular metallothionein concentrations, while cadmium caused a 9-20-fold increase in metallothionein over 18 h. Cadmium was a potent blocker of depolarization-stimulated 45Ca2+ uptake (IC50 = 4 microM), and the net uptake of cadmium measured with 109Cd2+ was less than 0.3% that of calcium. Although the rate of cadmium uptake was low relative to that of calcium, entry via voltage-sensitive calcium channels appeared to account for a significant portion of cadmium uptake; 109Cd2+ uptake at 30 min was increased 57% by high K+/BAY K8644, which facilitates entry through channels. Furthermore, calcium channel blockade with 100 nM nimodipine decreased total cell 109Cd2+ accumulation after 24 h by 63%. These data indicate that flux of cadmium through dihydropyridine-sensitive, voltage-sensitive calcium channels is a major mechanism for cadmium uptake by GH4C1 cells, and that pharmacologic blockade of calcium channels can afford dramatic protection against cadmium toxicity.