Endo T, Sakata M, Shaikh Z A
Faculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido, Japan.
Toxicol Appl Pharmacol. 1995 Oct;134(2):321-5. doi: 10.1006/taap.1995.1198.
The effects of pH, halide ions, and alkali metal ions on the uptake of inorganic mercury (Hg) were investigated in confluent primary cultures of rat renal cortical epithelial cells. The cells were incubated with 1 microM Hg in phosphate buffer at pH 5.5, 6.4, or 7.4 for 30 min at 37 degrees C. Incubation of cells at pH 5.5 resulted in a 22% increase in total Hg accumulation over those cells that were incubated at pH 7.4. Almost all of this increase was accounted for in the membrane fraction. In contrast, there was a 33% reduction in internalized Hg in cells incubated at pH 5.5. This may be explained by the conversion of hydroxide forms of Hg (Hg(OH)Cl and Hg(OH)2) to the chloride forms (HgCl2, HgCl3-, and HgCl4(2-) at a lower pH (decreased OH-) condition. In the presence of halide ions, the cells internalized Hg in the relative order of affinity of the halide ions for Hg2+ (i.e., F- < Cl- < Br- < I-). Br- and I- resulted in a 67 and 142% increase in internalized Hg over that by Cl-. The relatively high membrane binding and internalization of Hg in the presence of Br- and I- was possibly due to the formation of highly lipophilic complexes of Hg (i.e., HgBr2 and HgI2). The replacement of NaCl in the incubation medium by KCl caused a 36% decrease in internalized Hg. LiCl had a similar effect on the internalization of Hg. The above results suggest that in rat renal proximal tubules Hg uptake involves Na(+)- and H(+)-dependent mechanisms.
在大鼠肾皮质上皮细胞的汇合原代培养物中，研究了pH值、卤离子和碱金属离子对无机汞（Hg）摄取的影响。将细胞在含有1 microM汞的磷酸盐缓冲液中，于pH 5.5、6.4或7.4条件下，在37℃孵育30分钟。在pH 5.5条件下孵育的细胞，其总汞积累量比在pH 7.4条件下孵育的细胞增加了22%。几乎所有这种增加都归因于膜部分。相反，在pH 5.5条件下孵育的细胞中内化汞减少了33%。这可能是由于在较低pH值（OH-减少）条件下，汞的氢氧化物形式（Hg(OH)Cl和Hg(OH)2）转化为氯化物形式（HgCl2、HgCl3-和HgCl4(2-)）。在卤离子存在的情况下，细胞以卤离子对Hg2+的相对亲和顺序摄取汞（即F- < Cl- < Br- < I-）。Br-和I-导致内化汞比Cl-引起的内化汞分别增加了67%和142%。在Br-和I-存在的情况下，汞相对较高的膜结合和内化可能是由于形成了高度亲脂性的汞络合物（即HgBr2和HgI2）。用KCl替代孵育培养基中的NaCl导致内化汞减少36%。LiCl对汞的内化有类似影响。上述结果表明，在大鼠肾近端小管中，汞的摄取涉及Na(+)-和H(+)-依赖机制。
