Nitric oxide synthase distribution and expression with ischemic preconditioning of the rat liver.
This study was undertaken to identify nitric oxide synthase (NOS) isoforms responsible for the generation of cytoprotective NO during liver ischemic preconditioning (IPC). Sprague-Dawley rats were subjected to 45 min lobar ischemia followed by 2 h reperfusion. L-arginine or Nomega-nitro-L-arginine methyl ester (L-NAME) was administered to stimulate or block NO synthesis. Study groups (n=6) had 1) sham laparotomy, 2) ischemia reperfusion (IR), 3) IPC with 5 min ischemia and 10 min reperfusion before IR, 4) L-arginine before IR, or 5) L-NAME + IPC before IR. Liver function tests, nitrite + nitrate (NOx) and plasma amino acids were analyzed. The endothelial cell and inducible isoforms of NOS (eNOS and iNOS) were identified using immunohistochemistry and Western blotting. Both IPC and L-arginine treatment increased NOx (P<0.05) and improved serum liver enzymes (P<0.05) when compared with IR. These effects were prevented by L-NAME. Hepatic vein NOx was significantly higher than circulating NOx. iNOS expression was absent within the groups. The preconditioned livers were associated with up-regulation of eNOS expression and also increased L-arginine levels. The effects of L-arginine administration were similar to those evident following IPC. Thus, cytoprotective NO generation during IPC of the liver was a result of increased eNOS expression and increased L-arginine substrate availability.
Koti
Rahul S
RS
Academic Division of Surgical and Interventional Sciences, University College London, London, UK.
Tsui
Janice
J
Lobos
Edgar
E
Yang
Wenxuan
W
Seifalian
Alexander M
AM
Davidson
Brian R
BR
D000596:Amino Acids / Q000097:blood; D000818:Animals; D001120:Arginine / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D015153:Blotting, Western; D019610:Cytoprotection; D007150:Immunohistochemistry; D019194:Ischemic Preconditioning; D008099:Liver / Q000098:blood supply* / Q000201:enzymology* / Q000473:pathology; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II / Q000032:analysis*; D052250:Nitric Oxide Synthase Type III / Q000032:analysis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000201:enzymology
D000596:Amino Acids; D009569:Nitric Oxide; D001120:Arginine; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D019331:NG-Nitroarginine Methyl Ester