Small-intestinal absorption of cadmium and the significance of mucosal metallothionein
Small-intestinal absorption of cadmium and the significance of mucosal metallothionein
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DOI：
10.1177/096032719701600803
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发表时间：
1997-08-01
影响因子：
2.8
通讯作者：
Schafer, SG
中科院分区：
文献类型：
--
作者：
Elsenhans, B;Strugala, GJ;Schafer, SG
1虽然食物摄入是镉暴露的最重要途径之一，但对镉的肠道吸收机制知之甚少。在这方面，镉是大多数其他非必需的，仅仅是有毒金属的代表。2基于两个可区分的步骤的概念，肠道吸收镉的特点是在肠粘膜内的高积累和低速率的扩散转移到生物体中。3在摄入哺乳动物生物体后，镉被隔离到肝脏金属硫蛋白（MT）。据推测，肝脏Cd-MT然后逐渐重新分配镉到肾脏，这是慢性镉中毒的主要靶器官。4然而，当喂食低水平的饮食CdCl 2时，镉优先在肾脏中积累，在较小程度上在肝脏中积累，静脉内和口服Cd-MT复合物本身后也发现了这种分布模式。由于膳食镉诱导肠道MT，肠道Cd-MT复合物可能至少部分负责膳食镉的肾脏蓄积。5然而，对于这种机制，粘膜Cd-MT的Serenoglycan释放是必需的。事实上，在大鼠的体外研究结果表明，肠MT的浓度依赖性释放到小肠的serenum侧。这些结果表明，内源性肠道MT可能会提供Cd-MT到其他内脏器官，从而有助于优先肾蓄积摄入的镉。
1 Although food intake is among the most important routes of Cd exposure, not many details are known about the intestinal absorption mechanisms of Cd. In this respect Cd is representative of most other nonessential, merely toxic metals.2 Based on a concept of two distinguishable steps, intestinal absorption of Cd is characterized by high accumulation within the intestinal mucosa and a low rate of diffusive transfer into the organism.3 After uptake into the mammalian organism, Cd is sequestered into hepatic metallothionein (MT). It is assumed that hepatic Cd-MT then gradually redistributes Cd to the kidney, which is the main target organ for chronic Cd toxicity.4 When feeding low levels of dietary CdCl2, however, Cd accumulates preferentially in the kidney and to a lesser degree in the liver, a distribution pattern also found after intravenous and peroral administration of the Cd-MT complex itself. As dietary Cd induces intestinal MT, intestinal Cd-MT complexes could be at least partly responsible for the renal accumulation of dietary Cd.5 For this mechanism, however, serosal release of mucosal Cd-MT is required. In fact, in vitro findings in rats reveal a concentration-dependent release of intestinal MT to the serosal side of the small intestine. These results indicate that endogenous intestinal MT may deliver Cd-MT to other inner organs, thus contributing to the preferential renal accumulation of ingested Cd.