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l ‐[ 3 H]Nitroarginine and l ‐[ 3 H]Arginine Uptake into Rat Cerebellar Synaptosomes: Kinetics and Pharmacology
Author(s) -
Raghavendra Rao V. L.,
Butterworth R. F.
Publication year - 1996
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1996.67031275.x
Subject(s) - arginine , chemistry , nitroarginine , amino acid , biochemistry , nitric oxide , organic chemistry
Characteristics of the transport of the nitric oxide synthase substrate l ‐arginine and its inhibitor, N G ‐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 ( K m 1 = 0.72 m M , V max 1 = 0.98 nmol/min/mg of protein; K m 2 = 2.57 m M , V max 2 = 16.25 nmol/min/mg of protein). l ‐Arginine uptake was monophasic with a K m of 106 µ M and a V max of 0.33 nmol/min/mg of protein. l ‐NOARG uptake was selectively inhibited by l ‐NOARG, N G ‐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 N G ‐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.