Interference of L-arginine analogues with L-arginine transport mediated by the y+ carrier hCAT-2B

The inducible human cationic amino acid transporter hCAT-2B was expressed in Xenopus laevis oocytes, and this system was used to test the effect of several NO synthase (NOS) inhibitors and/or L-arginine analogues on L-arginine transport by this y(+) carrier, L-N-G-Methyl-L-arginine (L-NMA), asymmetrical L,N-G, N-G-dimethyl-L-arginine (L-ADMA), L-N-5-(1-iminoethyl)-ornithine (L-NIO), L-N-G-nitro-L-arginine (L-NNA), and L-N-G-nitro-L-arginine methyl ester (L-NAME) all inhibited the inducible NOS II extracted from RAW 264.7 macrophages induced with bacterial lipopolysaccharide. L-NMA, L-ADMA, and L-NIO also competed with L-arginine for transport by hCAT-2B, whereas L-NNA and L-NAME did not. The two L-arginine analogues, symmetrical N-G,N-G-dimethyl-L-arginine (L-SDMA) and alpha-amino-delta-isothioureidovaleric acid (AITV), as well as L-lysine, did not block enzymatic activity of NOS II, but did compete for L-arginine transport mediated by hCAT-2B, L-Lysine and L-SDMA were transported efficiently by hCAT-2B and exchanged against intracellular L-arginine, resulting in an L-arginine depletion of the cells, AITV was a much poorer substrate of hCAT-2B and had only little effect on intracellular L-arginine concentrations, These data indicate that substrate recognition differs markedly between the inducible L-arginine transporter hCAT-2B and the inducible NOS II, with different L-arginine analogues having affinity to only one or both of these proteins, (C) 1997 Academic Press.