Lind Y, Glynn A W
Toxicology Division, Swedish National Food Administration, Uppsala.
Pharmacol Toxicol. 1999 Jun;84(6):267-73. doi: 10.1111/j.1600-0773.1999.tb01493.x.
The complex binding of cadmium ions to humic and fulvic acids in water may influence the absorption and distribution of drinking-water Cd in humans. Thus, in the present study mice were given a single oral dose of Cd (109CdCl2, 25 microg/l) in 100 microl Millipore water containing different concentrations of humic compounds (0, 1, 10 and 100 mg dissolved organic carbon/l). The complex binding of Cd was studied by dialysis. At neutral pH, 1 mg dissolved organic carbon/l caused complex binding of more than 50% of the Cd, whereas more than 90% of Cd was bound at 10 and 100 mg dissolved organic carbon/l. At pH 3 the complex binding of Cd decreased somewhat, but over 90% of the Cd was bound at 100 mg dissolved organic carbon/l. Complex binding of Cd increased the lipid solubility of Cd, expressed as an octanol/ water partition coefficient, Nevertheless, more than 99% of the bound Cd was present as hydrophilic binding forms. Irrespective of the bound of Cd, the intestinal uptake and intracellular distribution (gel filtration on Sephadex G-75 column) were not affected by the humic substances 6 hr after dosage. Moreover, complex binding did not influence the intestinal absorption of Cd 24 hr after exposure. The median Cd retention in the kidneys of the 100 mg dissolved organic carbon/l group was 23% and 46% lower than that of the control group 6 and 24 hr after administration, respectively, indicating alterations in the distribution of Cd after absorption. Thus humic substances may affect the metabolism of toxic heavy metals, such as Cd, in vivo in mice, indicating that the presence of humic and fulvic acids in drinking water should be considered in future risk assessments of metals in drinking water.
镉离子与水中腐殖酸和富里酸的复杂结合可能会影响人体对饮用水中镉的吸收和分布。因此，在本研究中，给小鼠单次口服剂量的镉（109CdCl2，25微克/升），溶于含有不同浓度腐殖化合物（0、1、10和100毫克溶解有机碳/升）的100微升微孔水中。通过透析研究镉的复杂结合。在中性pH值下，1毫克溶解有机碳/升导致超过50%的镉发生复杂结合，而在10和100毫克溶解有机碳/升时，超过90%的镉被结合。在pH值为3时，镉的复杂结合有所下降，但在100毫克溶解有机碳/升时，超过90%的镉被结合。镉的复杂结合增加了镉的脂溶性，用正辛醇/水分配系数表示。然而，超过99%的结合镉以亲水性结合形式存在。无论镉的结合情况如何，给药6小时后，腐殖物质对肠道吸收和细胞内分布（在Sephadex G - 75柱上进行凝胶过滤）没有影响。此外，复杂结合在暴露24小时后不影响镉的肠道吸收。在100毫克溶解有机碳/升组中，给药后6小时和24小时，肾脏中镉的中位保留量分别比对照组低23%和46%，表明吸收后镉的分布发生了改变。因此，腐殖物质可能会影响小鼠体内有毒重金属如镉的代谢，这表明在未来饮用水中金属的风险评估中应考虑饮用水中腐殖酸和富里酸的存在。
