CADMIUM, ZINC, METALLOTHIONEIN AND KIDNEY TOXICITY

镉暴露是一个长期存在的人类毒理学问题。一 镉的主要作用部位是肾脏，在肾脏中，镉会产生一系列 肾小管对溶质，包括葡萄糖，氨基酸， 和磷酸盐。许多研究确定金属硫蛋白（MT）是 蛋白质在Cd 2+的细胞形态和毒性以及在 锌和铜的代谢。 金属簇合物的生物无机研究 为理解它在细胞中的某些行为提供了基础。 然而，无论是肾镉毒性的分子位点， 金属硫蛋白在亚急性镉毒性中的作用 和必需的金属代谢是很好理解的。在这方面， 申请提出了一套完整的假设和具体目标。 据认为，金属硫蛋白的两个结构域的结构允许 蛋白同时在细胞内Zn 2+分布中起作用， 在Cd 2+螯合中。这一想法将在小鼠肾小管中进行测试 细胞，利用新定义的Cd 2+缺陷引起特异性抑制 Na+-葡萄糖共转运无全身细胞毒性。它还将 在金属硫蛋白的模型研究中进行探索，以了解 蛋白质的细胞化学特性。主要问题是 讨论的内容包括：（1）受Cd 2+影响的细胞途径是什么， 导致Na+-葡萄糖共转运抑制？(2)什么是细胞 Cd ~（2+）形态与Na ~+-葡萄糖抑制关系 共同运输？(3)金属硫蛋白在锌代谢中的作用 受到镉结合的干扰(4)它的基本化学成分是什么 一种控制其在细胞锌和镉中反应的金属硫蛋白 新陈代谢和物种形成该提案涉及三名高级调查员 与互补的专业知识，SSB在文化和考试的 生物无机物中肾皮质细胞的运输特性，CFS 金属药物和蛋白质化学，以及细胞中的DHP 必需金属和有毒金属的形态及其性质 金属蛋白他们将使用放射性示踪剂来跟踪 Cd 2+对Na+-葡萄糖共转运，转运蛋白mRNA合成，转运蛋白 生物合成和降解与Cd ~（2+）c分布的关系。一个重点是 与Zn-MT蛋白的相互作用及Zn-MT在细胞内的分布 以及MT的诱导系统。相关动力学实验 MT及其分离的α和β结构域将进行建模 镉在细胞中的形态和定位过程。

Exposure to cadmium is a long standing problem in human toxicology. A principal size of action is the kidney, where cadmium produces a series of defects in tubular reabsorption of solutes, including glucose, amino acids, and phosphate. Numerous studies identify metallothionein (MT) as a key protein in the cellular speciation and toxicity of Cd2+ as well as in the metabolism of zinc and copper. Bioinorganic research on the metal clusters in MT provide a basis for understanding some of its behavior in cells. Nevertheless, neither the molecular site(s) of renal cadmium toxicity nor the detailed functional roles of metallothionein in subacute Cd toxicity and essential metal metabolism are well understood. In this context, this application sets forth an integrated set of hypotheses and specific aims. It is thought that the two domain structure of metallothionein permits the protein to function simultaneously in intracellular Zn2+ distribution and in Cd2+ sequestration. This idea will be tested in mouse renal tubule cells, using the newly defined defect of Cd2+ to cause specific inhibition of Na+-glucose co-transport without generalized cell toxicity. It will also be explored in model studies on metallothionein in order to understand chemically the cellular properties of the protein. Major questions to be addressed include (1) What are the cellular pathways affected by Cd2+ which lead to inhibition of Na+-glucose co-transport? (2) What is the cellular speciation of Cd2+ in relationship to inhibition of Na+-glucose co-transport? (3) Is the role of metallothionein in zinc metabolism perturbed by cadmium-binding? (4) What is the underlying chemistry of metallothionein that governs its reactivity in cellular zinc and cadmium metabolism and speciation? The proposal involves three senior investigators with complementary expertise, SSB in the culture and examination of the transport properties of kidney cortical cells, CFS in the bioinorganic chemistry of metallo-drugs and -proteins, and DHP in the cellular speciation of essential and toxic metals and the properties of metalloproteins. They will employ radiotracers to follow the effects of Cd2+ on Na+-glucose co-transport, transporter mRNA synthesis, transporter biosynthesis and degradation in relation to Cd2+c distribution. A focus is on its interaction with Zn-MT protein and intracellular distribution of zinc as well as the induction system for MT. Related kinetic experiments on MT and its isolated alpha- and beta-domains will be carried out to model the process of cadmium speciation and localization in cells.