Institute of Experimental and Clinical Pharmacology and Toxicology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Fahrstrasse 17, 91054, Erlangen, Germany.
Amino Acids. 2020 Jul;52(6-7):975-985. doi: 10.1007/s00726-020-02867-8. Epub 2020 Jul 8.
Elevated plasma concentrations of the uremic toxin asymmetric dimethylarginine (ADMA) and low plasma concentrations of L-homoarginine are independently associated with cardiovascular events and mortality. Key enzymes involved in the homeostasis of both arginine derivatives are expressed in proximal tubule cells of the kidney. To get access to these enzymes, transport proteins are important. One of the transporters mediating the transport of ADMA and L-homoarginine is the solute carrier superfamily (SLC) member OATP4C1, located in the basolateral membrane of proximal tubule cells. To gain insights into the role of export pumps in the transport of both substances, we established a double-transfected MDCK cell line expressing OATP4C1 and the export pump P-glycoprotein (P-gp). Using MDCK cell monolayers, we demonstrated in time-dependent and concentration-dependent vectorial transport experiments that ADMA and L-homoarginine are transported from the basolateral to the apical compartment of MDCK-OATP4C1-P-gp cells with significantly higher transport rates compared to single-transfected MDCK-OATP4C1, MDCK-P-gp and MDCK-VC (control) cells (e.g. transport ratio MDCK-OATP4C1-P-gp/MDCK-VC: for 50 µM ADMA = 2.0-fold, for 50 µM L-homoarginine = 3.4-fold). These results indicate that both OATP4C1 and P-gp transport the arginine derivatives ADMA and L-homoarginine and are, therefore, important for the homoeostasis of both substances.
尿毒症毒素不对称二甲基精氨酸 (ADMA) 的血浆浓度升高和 L-同型精氨酸的血浆浓度降低与心血管事件和死亡率独立相关。参与这两种精氨酸衍生物体内平衡的关键酶在肾脏近端肾小管细胞中表达。为了获得这些酶，转运蛋白很重要。介导 ADMA 和 L-同型精氨酸转运的转运蛋白之一是溶质载体家族 (SLC) 成员 OATP4C1，位于近端肾小管细胞的基底外侧膜。为了深入了解输出泵在这两种物质转运中的作用，我们建立了一个双转染 MDCK 细胞系，表达 OATP4C1 和外排泵 P-糖蛋白 (P-gp)。使用 MDCK 细胞单层，我们在时间和浓度依赖性载体转运实验中证明，ADMA 和 L-同型精氨酸从 MDCK-OATP4C1-P-gp 细胞的基底外侧向顶端腔室进行转运，与单转染 MDCK-OATP4C1、MDCK-P-gp 和 MDCK-VC（对照）细胞相比，转运速率显著更高（例如，转运比 MDCK-OATP4C1-P-gp/MDCK-VC：对于 50µM ADMA=2.0 倍，对于 50µM L-同型精氨酸=3.4 倍）。这些结果表明，OATP4C1 和 P-gp 均转运精氨酸衍生物 ADMA 和 L-同型精氨酸，因此对这两种物质的体内平衡很重要。
