Studies of l-Arginine Transport in Bovine Aortic Endothelial Cells

We have previously demonstrated that p1,p4-diadenosine 5′-tetraphosphate induces the release of NO and modulates the uptake of l-arginine by bovine aortic endothelial cells (BAEC) [Hilderman, R. H., and Christensen, E. F. (1998) FEBS Lett. 407, 320–324; Hilderman, R. H., Casey, T. E., and Pojoga, L. H. (2000) Arch. Biochem. Biophys. 375, 124–130]. In this communication we characterize the uptake of l-Arg by BAEC. l-Arg is transported into BAEC by at least two different transporter systems. One transporter system is protein synthesis dependent, and l-Arg transported by this system is incorporated into proteins. The second transporter system involved in l-Arg uptake is protein synthesis independent, and uptake occurs by facilitated diffusion. The l-Arg transported by facilitated diffusion is metabolized into l-argininosuccinate. Homologous and heterologous competition uptake studies were performed using a fixed concentration of radiolabeled l-Arg, l-lysine, and l-leucine with varying concentrations of competing nonradiolabeled amino acids. The results of these competition uptake studies are consistent with the protein-synthesis-dependent uptake of l-Arg taking place through a transporter system that is highly specific for l-Arg and with the facilitated diffusion uptake taking place through a transporter that is specific for l-Arg and l-Leu.