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Characterization of Neuronal Amino Acid Transporters: Uptake of Nitric Oxide Synthase Inhibitors and Implication for Their Biological Effects
Author(s) -
Schmidt Kurt,
List Barbara M.,
Klatt Peter,
Mayer Bernd
Publication year - 1995
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.1471-4159.1995.64041469.x
Subject(s) - arginine , amino acid , chemistry , biochemistry , nitric oxide synthase , ornithine , nitric oxide , phenylalanine , leucine , enzyme , organic chemistry
In the present study we investigated uptake of the nitric oxide (NO) synthase inhibitors N G ‐methyl‐ l ‐arginine and N G ‐nitro‐ l ‐arginine by the mouse neuroblastoma × rat glioma hybrid cell line NG108‐15. Uptake of N G ‐methyl‐ l ‐arginine was characterized by biphasic kinetics ( K m1 = 8 µmol/L, V max1 = 0.09 nmol × mg −1 × min −1 ; K m2 = 229 µmol/L, V max2 = 2.9 nmol × mg −1 × min −1 ) and was inhibited by basic but not by neutral amino acids. Uptake of N G ‐nitro‐ l ‐arginine followed Michaelis‐Menten kinetics ( K m = 265 µmol/L, V max = 12.8 ± 0.86 nmol × mg −1 × min −1 ) and was selectively inhibited by aromatic and branched chain amino acids. Further characterization of the transport systems revealed that uptake of N G ‐methyl‐ l ‐arginine is mediated by system y + , whereas systems L and T account for the transport of N G ‐nitro‐ l ‐arginine. In agreement with these data on uptake of the inhibitors, l ‐lysine and l ‐ornithine antagonized the inhibitory effects of N G ‐methyl‐ l ‐arginine on bradykinin‐induced intracellular cyclic GMP accumulation, whereas l ‐tryptophan, l ‐phenylalanine, and l ‐leucine interfered with the effects of N G ‐nitro‐ l ‐arginine. These data suggest that rates of uptake are limiting for the biological effects of NO synthase inhibitors.