ISSN:
1471-4159
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Medizin
Notizen:
Abstract: Characteristics of the transport of the nitric oxide synthase substrate l-arginine and its inhibitor, NG-nitro-l-arginine (l-NOARG), into rat cerebellar synaptosomes were studied. Uptake of both l-arginine and l-NOARG was linear with increasing amount of protein (up to 40 µg) and time of incubation (up to 5 min) at 37°C. Uptake of both compounds reached a steady state by 20 min. Maximal uptake of l-NOARG (650 pmol/mg of protein) was three to four times higher than that of l-arginine (170 pmol/mg of protein). l-NOARG uptake showed biphasic kinetics (Km 1 = 0.72 mM, Vmax 1 = 0.98 nmol/min/mg of protein; Km 2 = 2.57 mM, Vmax 2 = 16.25 nmol/min/mg of protein). l-Arginine uptake was monophasic with a Km of 106 µM and a Vmax of 0.33 nmol/min/mg of protein. l-NOARG uptake was selectively inhibited by l-NOARG, NG-nitro-l-arginine methyl ester, and branched-chain and aromatic amino acids. l-Alanine and l-serine also inhibited l-NOARG uptake but with less potency. Uptake of l-arginine was selectively inhibited by NG-monomethyl-l-arginine acetate and basic amino acids. These studies suggest that in rat cerebellar synaptosomes, l-NOARG is transported by the neutral amino acid carrier systems T and L with high affinity, whereas l-arginine is transported by the basic amino acid carrier system y+ with high affinity. These data indicate that the concentration of competing amino acids is an important factor in determining the rates of uptake of l-NOARG and l-arginine into synaptosomes and, in this way, may control the activity of nitric oxide synthase.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1046/j.1471-4159.1996.67031275.x
