Zalups Rudolfs K, Ahmad Sarfaraz
Division of Basic Medical Sciences, Mercer University, School of Medicine, Macon, Georgia 31207, USA.
Kidney Int. 2005 Oct;68(4):1684-99. doi: 10.1111/j.1523-1755.2005.00585.x.
The activity of the organic anion transporter 1 (OAT1) has been implicated recently in the basolateral uptake of thiol conjugates of inorganic mercury in renal proximal tubular cells. However, very little is known about the role of OAT1 in the renal epithelial transport of organic forms of mercury, such as methylmercury (CH(3)Hg(+)), especially when it is in the form of the cysteine (Cys) S-conjugate of methylmercury (CH(3)Hg-Cys), which is believed to be a biologically relevant form of mercury.
Accordingly, the present study, was designed to characterize the transport of CH(3)Hg-Cys in Madin-Darby canine kidney (MDCK) cells transfected stably with the human isoform of OAT1 (hOAT1) and in proximal tubular-derived NRK-52E cells.
Data on saturation kinetics, time dependency, substrate specificity, and temperature dependency demonstrate that CH(3)Hg-Cys is transported by hOAT1. Substrate-specificity data from the control cells also show that CH(3)Hg-Cys is a substrate of one or more transporter(s) that is/are not hOAT1. Additional findings indicate that at least one amino acid transport system is involved in the uptake of CH(3)Hg-Cys in MDCK cells. Furthermore, in the presence of cytotoxic concentrations of CH(3)Hg-Cys, rates of survival were lower in hOAT1-transfected cells than in wild-type control cells.
The present data demonstrate clearly that CH(3)Hg-Cys is indeed a transportable substrate of OAT1. Moreover, the collective findings from the MDCK cells and NRK-52E cells infer that CH(3)Hg-Cys is a likely transportable mercuric species in proximal tubular epithelial cells that is taken up in vivo by both OAT1 and amino acid transporters.
有机阴离子转运体1（OAT1）的活性最近被认为与肾近端小管细胞中无机汞硫醇结合物的基底外侧摄取有关。然而，关于OAT1在有机汞形式（如甲基汞（CH(3)Hg(+)））的肾上皮转运中的作用，人们了解甚少，尤其是当它以甲基汞的半胱氨酸（Cys）S结合物（CH(3)Hg-Cys）形式存在时，这种形式被认为是汞的一种生物学相关形式。
因此，本研究旨在表征在稳定转染人OAT1同工型（hOAT1）的Madin-Darby犬肾（MDCK）细胞和近端小管来源的NRK-52E细胞中CH(3)Hg-Cys的转运情况。
关于饱和动力学、时间依赖性、底物特异性和温度依赖性的数据表明，CH(3)Hg-Cys可被hOAT1转运。对照细胞的底物特异性数据还表明，CH(3)Hg-Cys是一种或多种非hOAT1转运体的底物。其他研究结果表明，至少一种氨基酸转运系统参与了MDCK细胞中CH(3)Hg-Cys的摄取。此外，在细胞毒性浓度的CH(3)Hg-Cys存在下，hOAT1转染细胞的存活率低于野生型对照细胞。
目前的数据清楚地表明，CH(3)Hg-Cys确实是OAT1的可转运底物。此外，MDCK细胞和NRK-52E细胞的综合研究结果推断，CH(3)Hg-Cys可能是近端小管上皮细胞中一种可转运的汞物种，在体内可被OAT1和氨基酸转运体摄取。
