Institute of Experimental and Clinical Pharmacology and Toxicology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Fahrstraße 17, 91054 Erlangen, Germany.
J Mol Cell Cardiol. 2012 Sep;53(3):392-400. doi: 10.1016/j.yjmcc.2012.06.002. Epub 2012 Jun 15.
Elevated plasma concentrations of endogenously formed asymmetric (ADMA) and symmetric dimethyl-l-arginine (SDMA) are associated with adverse clinical outcomes. Our aim was to investigate the cellular uptake properties of ADMA by the human cationic amino acid transporter 1 (CAT1; SLC7A1). Human embryonic kidney cells (HEK293) stably overexpressing CAT1 (HEK-CAT1) and vector-transfected control cells (HEK-VC) were established to determine cellular uptake of labeled [(3)H]ADMA and [(3)H]l-arginine. Uptake of ADMA and l-arginine were significantly (p<0.001) higher in HEK-CAT1 than in HEK-VC at all investigated concentrations. Apparent V(max) values of cellular ADMA and l-arginine uptake by CAT1 were 26.9 ± 0.8 and 11.0 ± 0.2 nmol mg protein(-1) min(-1), respectively. K(m) values were 183 ± 21 μmoll(-1) (ADMA) and 519 ± 36 μmoll(-1) (l-arginine). Uptake of ADMA was inhibited by l-arginine and SDMA with IC(50) values (95% CI) of 227 (69-742) μmoll(-1) and 273 (191-390) μmoll(-1), respectively. ADMA and SDMA inhibited CAT1-mediated uptake of l-arginine with IC(50) values of 758 (460-1251) μmoll(-1) and 789 (481-1295) μmoll(-1), respectively. Efflux of ADMA was significantly increased in HEK-CAT1 cells as compared to HEK-VC (p<0.05). CAT1 mediates the cellular uptake of ADMA. In its physiological concentration range ADMA is unlikely to impair CAT1-mediated transport of l-arginine. Conversely, high (but still physiological) concentrations of l-arginine can inhibit CAT1-mediated cellular uptake of ADMA.
内源性形成的不对称（ADMA）和对称二甲基-l-精氨酸（SDMA）的血浆浓度升高与不良临床结局相关。我们的目的是研究人阳离子氨基酸转运蛋白 1（CAT1；SLC7A1）对 ADMA 的细胞摄取特性。建立了稳定过表达 CAT1 的人胚肾细胞（HEK293）（HEK-CAT1）和载体转染对照细胞（HEK-VC），以确定标记的 [(3)H]ADMA 和 [(3)H]l-精氨酸的细胞摄取。在所有研究的浓度下，ADMA 和 l-精氨酸在 HEK-CAT1 中的摄取均明显（p<0.001）高于 HEK-VC。CAT1 细胞 ADMA 和 l-精氨酸摄取的表观 V(max)值分别为 26.9 ± 0.8 和 11.0 ± 0.2 nmol mg 蛋白(-1) min(-1)。K(m)值分别为 183 ± 21 μmoll(-1)（ADMA）和 519 ± 36 μmoll(-1)（l-精氨酸）。ADMA 的摄取被 l-精氨酸和 SDMA 抑制，IC(50)值（95%CI）分别为 227（69-742）μmoll(-1)和 273（191-390）μmoll(-1)。ADMA 和 SDMA 抑制 CAT1 介导的 l-精氨酸摄取，IC(50)值分别为 758（460-1251）μmoll(-1)和 789（481-1295）μmoll(-1)。与 HEK-VC 相比，ADMA 在 HEK-CAT1 细胞中的外排明显增加（p<0.05）。CAT1 介导 ADMA 的细胞摄取。在其生理浓度范围内，ADMA 不太可能损害 CAT1 介导的 l-精氨酸转运。相反，高（但仍为生理）浓度的 l-精氨酸可以抑制 CAT1 介导的 ADMA 细胞摄取。
