title: Tyrosine phosphorylation of neuronal nitric oxide synthase (nNOS) during hypoxia in the cerebral cortex of newborn piglets: the role of nitric oxide.
abstract: The present study aims to investigate the mechanism of activation of nNOS during hypoxia and tests the hypothesis that the hypoxia-induced increased tyrosine phosphorylation of nNOS in the cerebral cortical membranes of newborn piglets is mediated by nNOS-derived nitric oxide (NO). Fifteen newborn piglets were divided into normoxic (Nx, n=5), hypoxic (Hx, n=5) and hypoxic-pretreated with nNOS inhibitor I (Hx-nNOSi) groups. Hypoxia was induced by an FiO(2) of 0.07 for 60 min. nNOS inhibitor I (selectivity>2500 vs endothelial NOS and >500 vs inducible NOS) was administered (0.4 mg/kg, i.v.) 30 min prior to hypoxia. Cortical membranes were isolated and tyrosine phosphorylation of nNOS determined by Western blot. Membrane protein was immunoprecipitated with nNOS antibody, separated on 12% SDS-PAGE and blotted with anti-phosphotyrosine antibody. Protein bands were detected by enhanced chemiluminescence, analyzed by densitometry and expressed as absorbance (OD x mm(2)). Density (OD x mm(2)) of tyrosine phosphorylated nNOS was 51.66+/-14.11 in Nx, 118.39+/-14.17 in Hx (p<0.05 vs Nx) and 45.56+/-10.34 in Hx-nNOSi (p<0.05 vs Hx, p=NS vs Nx). The results demonstrate that pretreatment with nNOS inhibitor prevents the hypoxia-induced increased tyrosine phosphorylation of nNOS. We conclude that the mechanism of hypoxia-induced increased tyrosine phosphorylation of nNOS is mediated by nNOS-derived NO.
authors: Department of Pediatrics, Drexel University College of Medicine and St. Christopher's, Hospital for Children, Philadelphia, PA 19102, USA. omprakash.mishra@drexelmed.edu
authors: Om Prakash
authors: OP
authors: Mishra
authors: Qazi M
authors: QM
authors: Ashraf
authors: Maria
authors: M
authors: Delivoria-Papadopoulos
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D003720:Densitometry; D004591:Electrophoresis, Polyacrylamide Gel; D000860:Hypoxia / Q000188:drug therapy / Q000378:metabolism*; D049449:Luminescence; D009569:Nitric Oxide / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011897:Random Allocation; D013552:Swine; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D010725:Phosphocreatine; D009569:Nitric Oxide; D014443:Tyrosine; D000255:Adenosine Triphosphate; D052248:Nitric Oxide Synthase Type I