L-Arginine transport is augmented through up-regulation of tubular CAT-2 mRNA in ischemic acute renal failure in rats.
BACKGROUND
Ischemic acute renal failure (iARF) is associated with increased nitric oxide (NO) production during the reperfusion period, as endothelial nitric oxide synthase (eNOS) is maximally activated, and renal tubular inducible NOS (iNOS) is stimulated. Increased NO production leads to augmented tubular injury, probably through the formation of peroxynitrite. l-Arginine (l-Arg), the only precursor for NO, is transported into cells by cationic amino acid transporters, CAT-1 and CAT-2. We hypothesized that the increased NO production observed in iARF may result from increased l-Arg uptake, which would be reflected in the augmented expression of l-Arg transporter(s).


METHODS
Ischemic acute renal failure was induced in rats by right nephrectomy + left renal artery clamping for 60 minutes. l-Arg uptake was examined in freshly harvested glomeruli and tubuli from control, sham operated, and animals subjected to 15, 30, and 60 minutes, and 24 hours of reperfusion, following 60 minutes of ischemia. Using RT-PCR, renal tissues were examined further for the expression of iNOS, CAT-1, CAT-2, arginase I and arginase II.


RESULTS
Tubular expression of iNOS mRNA was initiated by ischemia, continued to increase after 60 minutes of reperfusion, and decreased after 24 hours. l-Arg transport into glomeruli was similar in all experimental groups. l-Arg uptake into tubuli was markedly augmented following the 60-minute reperfusion, while it moderately increased after 24 hours of reperfusion. This was accompanied by a parallel, preferential increase in tubular CAT-2 mRNA expression at 60 minutes of reperfusion. CAT-1 mRNA expression was unchanged, as detected by RT-PCR. In addition, the expression of arginase II and arginase I mRNA was attenuated by 30 minutes and one hour of reperfusion, and returned to baseline values after 24 hours of reperfusion.


CONCLUSIONS
Ischemic ARF is associated with augmented tubular CAT-2 mRNA expression, which leads to enhanced l-Arg transport and increased NO production. This may contribute to the renal injury exhibited in iARF.
Schwartz
Idit F
IF
The Tel Aviv Sourasky Medical Center, Tel Aviv, Israel.
Schwartz
Doron
D
Traskonov
Marina
M
Chernichovsky
Tamara
T
Wollman
Yoram
Y
Gnessin
Ehud
E
Topilsky
Ian
I
Levo
Yoram
Y
Iaina
Adrian
A
D058186:Acute Kidney Injury / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D000818:Animals; D001119:Arginase / Q000235:genetics; D001120:Arginine / Q000493:pharmacokinetics*; D001692:Biological Transport / Q000502:physiology; D027201:Cationic Amino Acid Transporter 1 / Q000235:genetics / Q000378:metabolism; D027202:Cationic Amino Acid Transporter 2 / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D007511:Ischemia / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D007684:Kidney Tubules / Q000378:metabolism* / Q000473:pathology; D007770:L-Lactate Dehydrogenase / Q000652:urine; D008297:Male; D019001:Nitric Oxide Synthase / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D014316:Tritium; D015854:Up-Regulation / Q000502:physiology
D027201:Cationic Amino Acid Transporter 1; D027202:Cationic Amino Acid Transporter 2; D012333:RNA, Messenger; D014316:Tritium; D001120:Arginine; D007770:L-Lactate Dehydrogenase; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D001119:Arginase