INTERACTIONS BETWEEN METALS IN RAT JEJUNUM - IMPLICATIONS ON THE NATURE OF CADMIUM UPTAKE
INTERACTIONS BETWEEN METALS IN RAT JEJUNUM - IMPLICATIONS ON THE NATURE OF CADMIUM UPTAKE
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DOI：
10.1016/0300-483x(85)90118-0
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发表时间：
1985-01-01
期刊：
影响因子：
4.5
通讯作者：
FOULKES, EC
中科院分区：
文献类型：
--
作者：
FOULKES, EC
从大鼠空肠腔中摄取镉的特征在于明显的饱和性和对锌和钙抑制的敏感性。多种其他重金属也抑制肠道镉转运。这一假设进行了测试，镉竞争与其他金属的运输系统。所观察到的差异之间的明显Ki和KM值之间的相互作用镉和锌反对竞争。此外，Zn、Ca和La对Cd吸收的抑制在系统接近部分表观饱和（5-100 μ M）的范围内与Cd浓度无关。相对高浓度的其他多价阳离子，包括镉本身和铅，镍，铬3+，锶，镁和聚赖氨酸，也抑制109镉的吸收。建议的可能性，这些阳离子非特异性中和膜电荷，从而干扰膜结合和随后的内化109镉。这一解释排除了不太可能的假设，即特定的膜载体存在，以促进吸收的有毒和非必需的金属，如镉的需要。
Cadmium uptake from the lumen of the rat jejunum is characterized by apparent saturability and by sensitivity to inhibition by Zn and Ca. A variety of other heavy metals also inhibit intestinal Cd transport. The hypothesis was tested that Cd competes with other metals for their transport systems. The observed discrepancy between the apparent Ki and KM values for interaction between Cd and Zn argues against competition. Further, inhibition of Cd uptake by Zn, Ca and La is independent of Cd concentration over the range in which the system approaches partial apparent saturation (5-100 .mu.M). Relatively high concentrations of other polyvalent cations, including Cd itself and Pb, Ni, Cr3+, Sr, Mg and polylysine, also depress 109Cd uptake. The possibility is suggested that these cations non-specifically neutralize membrane charges, and thus interfere with membrane binding and subsequent internalization of 109Cd. This explanation obviates the need for the unlikely assumption that specific membrane carriers exist to facilitate uptake of a toxic and non-essential metal like Cd.