Oxidative stress during post-hypoxic-ischemic reperfusion in the newborn lamb: the effect of nitric oxide synthesis inhibition.
Post-hypoxic-ischemic (HI) reperfusion induces endothelium and neurons to produce excessive amounts of nitric oxide and superoxide, leading to peroxynitrite formation, release of protein-bound metal ions (i.e. iron), and cytotoxic oxidants. We produced severe HI in 18 newborn lambs and serially determined plasma prooxidants (non-protein-bound iron), lipid peroxidation (malondialdehyde), and antioxidative capacity [ratio of ascorbic acid/dehydroascorbic acid (AA/DHA), alpha-tocopherol, sulfhydryl groups, allantoin/uric acid ratio, and vitamin A] in blood effluent from the brain before and at 15, 60, 120, and 180 min after HI. The lambs were divided in three groups: six received a placebo (CONT), six received low dose (10 mg/kg/i.v.) N omega-nitro-L-arginine (NLA-10) to block nitric oxide production, and six received high dose NLA (40 mg/kg/i.v.; NLA-40), immediately after completion of HI. Non-protein-bound iron increased in all groups after HI but was significantly lower in both NLA groups at 180 min post-HI (p < 0.05), the AA/DHA ratio showed a consistent decrease in CONT (at 60 min post-HI, p < 0.05), but remained stable in NLA lambs. alpha-Tocopherol decreased steadily in the CONT, but not in the NLA lambs [180 post-H: 1.9 +/- 0.9 versus 4.2 +/- 0.7 microM (NLA-40), p < 0.05). Malondialdehyde was significantly higher in CONT lambs 120 min post-H compared with NLA groups [0.61 +/- 017 versus 0.44 +/- 0.05 microM (NLA-40), p < 0.05]. Vitamin A and sulfhydryl groups did not differ among groups. We conclude that post-H inhibition of nitric oxide synthesis diminishes non-protein-bound iron increment and preserves antioxidant capacity.
Dorrepaal
C A
CA
Department of Pediatrics (Division of Neonatology), Leiden University Hospital, The Netherlands.
van Bel
F
F
Moison
R M
RM
Shadid
M
M
van de Bor
M
M
Steendijk
P
P
Berger
H M
HM
D000818:Animals; D000831:Animals, Newborn; D000975:Antioxidants / Q000378:metabolism; D002545:Brain Ischemia / Q000188:drug therapy*; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D004791:Enzyme Inhibitors / Q000627:therapeutic use*; D002534:Hypoxia, Brain / Q000188:drug therapy*; D015227:Lipid Peroxidation / Q000187:drug effects; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D019335:Nitroarginine / Q000627:therapeutic use*; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000187:drug effects; D015427:Reperfusion Injury / Q000188:drug therapy*; D012756:Sheep
D000975:Antioxidants; D004791:Enzyme Inhibitors; D019335:Nitroarginine; D019001:Nitric Oxide Synthase