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Membrane Transport of Neuronal Nitric Oxide Synthase Substrate l ‐Arginine Is Constitutively Expressed with CAT1 and 4F2hc, but Not CAT2 or rBAT
Author(s) -
Stevens Bruce R.,
Vo Chi B.
Publication year - 1998
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.1471-4159.1998.71020564.x
Subject(s) - arginine , microbiology and biotechnology , messenger rna , biology , northern blot , amino acid , biochemistry , nitric oxide , nitric oxide synthase , gene isoform , enzyme , endocrinology , gene
The potential induction of cationic and zwitter‐ionic amino acid transport systems and mRNA transcripts was investigated in primary neuronal cultures from rat hypothalamus/brainstem. Cultures exposed to bacterial lipopolysaccharide (LPS) plus interferon‐γ (IFNγ) were assessed with respect to northern blot analyses, l ‐leucine/ l ‐arginine cross‐inhibition uptake profiles in the presence and absence of Na + , and initial rate sodium‐independent l ‐arginine transport kinetics. l ‐Arginine uptake activity was constitutively expressed along with uninduced steady‐state levels of CAT1 and 4F2hc transcripts. However, neither the high‐affinity nor the low‐affinity alternatively spliced inducible isoforms of CAT2 or CAT2a transcripts (encoding system y + in control astrocytes, lymphocytes, or liver) nor the rBAT transcripts (encoding system b o,+ in control intestinal epithelial cells) were detected by northern analysis of neuronal mRNA. Cross‐inhibition profiles were consistent with physiologic system y + activity, but not system b o,+ or system y + L. Transport kinetics gave a single component with V max = 113 ± 7 pmol/min/mg of protein and K m = 47 ± 8 µ M l ‐arginine; these kinetic parameters were not influenced by addition of LPS/IFNγ at concentrations that up‐regulated CAT2 mRNA and system y + activity in control astroglia from the same area of the brain. The data are consistent with l ‐arginine membrane uptake occurring via only system y + encoded by constitutive CAT1, with possible physiologic contribution by constitutive 4F2hc transcripts in primary neuronal cultures.