Studies of L-arginine transport in bovine aortic endothelial cells

We have previously demonstrated that p(1),p(4)-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.