Characterization of L-arginine transporters in rat renal inner medullary collecting duct.
Previous work from our laboratory has demonstrated that the inner medullary collecting duct (IMCD) expresses a large amount of nitric oxide synthase (NOS) activity. The present study was designed to characterize the transport of NOS substrate, L-arginine, in a suspension of bulk-isolated IMCD cells from the Sprague-Dawley rat kidney. Biochemical transport studies demonstrated an L-arginine transport system in IMCD cells that was saturable and Na(+) independent (n = 6). L-Arginine uptake by IMCD cells was inhibited by the cationic amino acids L-lysine, L-homoarginine, and L-ornithine (10 mmol/l each) and unaffected by the neutral amino acids L-leucine, L-serine, and L-glutamine. Both L-ornithine (n = 6) and L-lysine (n = 6) inhibited NOS enzymatic activity in a dose-dependent manner in IMCD cells, supporting the important role of L-arginine transport for NO production by this tubular segment. Furthermore, RT-PCR of microdissected IMCD confirmed the presence of cationic amino acid transporter CAT1 mRNA, whereas CAT2A, CAT2B, and CAT3 were not detected. These results indicate that L-arginine uptake by IMCD cells occurs via system y(+), is encoded by CAT1, and may participate in the regulation of NO production in this renal segment.
Wu
F
F
Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
Cholewa
B
B
Mattson
D L
DL
D026905:Amino Acid Transport Systems; D000818:Animals; D001120:Arginine / Q000493:pharmacokinetics*; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002412:Cations / Q000493:pharmacokinetics; D002956:Citrulline / Q000096:biosynthesis; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression / Q000502:physiology; D006706:Homeostasis / Q000502:physiology; D007679:Kidney Medulla / Q000737:chemistry / Q000201:enzymology*; D007685:Kidney Tubules, Collecting / Q000737:chemistry / Q000201:enzymology*; D008239:Lysine / Q000493:pharmacokinetics; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D009952:Ornithine / Q000493:pharmacokinetics; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D013379:Substrate Specificity; D014316:Tritium; D014882:Water-Electrolyte Balance / Q000502:physiology; D015091:beta-Alanine / Q000031:analogs & derivatives / Q000494:pharmacology; D019323:omega-N-Methylarginine / Q000494:pharmacology
D026905:Amino Acid Transport Systems; D002352:Carrier Proteins; D002412:Cations; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D014316:Tritium; D015091:beta-Alanine; C012924:2,2-dimethyl-beta-alanine; D019323:omega-N-Methylarginine; D002956:Citrulline; D001120:Arginine; D009952:Ornithine; D019001:Nitric Oxide Synthase; D008239:Lysine; D019331:NG-Nitroarginine Methyl Ester