y+ LAT-1 mediates transport of the potent and selective iNOS inhibitor, GW274150, in control J774 macrophages

This study has characterised the transport mechanism(s) for the novel and selective inhibitor of inducible nitric oxide synthase (iNOS), GW274150, in murine macrophage J774 cells. Transport of GW274150 was saturable (Km = 0.24 ± 0.01 mM and Vmax of 8.5 ± 0.12 pmol·µg protein−1 min−1), pH-insensitive and largely Na+-independent. Transport was also susceptible to trans-stimulation and was significantly inhibited by a 10-fold excess of L-arginine, L-lysine, L-leucine, L-methionine, L-glutamine and 6-diazo-5-oxo-L-norleucine but not by other amino acids or by N-ethylmaleimide. More importantly, the inhibitions caused by the neutral amino acids were critically dependent on Na+. These results strongly implicate system y+L in the transport of GW274150. Northern blot analysis confirmed this by revealing the presence of transcripts for y+LAT-1 but not y+LAT-2. Thus, taken together, our data show for the first time that J774 macrophages express y+LAT-1 transporters and that these carriers mediate transport of GW2741500 at least in these cells.