title: Nitric oxide synthase in acute alteration of nitric oxide levels after subarachnoid hemorrhage.
abstract: OBJECTIVE
  Subarachnoid hemorrhage (SAH) is associated with acute decreases and subsequent recovery of cerebral nitric oxide (NO) levels, but the mechanisms of these alterations are not known. In this study, we measured NO synthase (NOS) protein and kinetics to determine its involvement in the alterations of cerebral NO levels after SAH.
  
  
  METHODS
  The endovascular rat model of SAH was used. The number of NOS-1 (neuronal) and NOS-2 (inducible)-positive cells (0-96 h) was determined by counting immunoreactive cells in 8-microm cryostat sections. The tissue content of active NOS and its kinetic parameters were studied with an enzymatic l-citrulline assay.
  
  
  RESULTS
  The number of NOS-1-positive cells increased between 1 and 3 hours after SAH, decreased to and below control values at 6 and 72 hours after SAH, and increased to control values 96 hours after SAH. The number of NOS-2-positive cells increased 1 hour after SAH, decreased to control values at 24 hours, and increased above control values 96 hours after SAH. The Michaelis-Menten kinetic parameters (V(max), K(m), slope) of NOS remained unchanged at 10 and 90 minutes after SAH.
  
  
  CONCLUSIONS
  NOS-1 and -2 proteins undergo a triphasic alteration after SAH, whereas the amount of active NOS and its kinetic parameters remain unchanged during the first 90 minutes after SAH. Depletion of NOS is not involved in the acute alterations of cerebral NO levels after SAH.
authors.affiliation: Department of Neurosurgery, Mount Sinai School of Medicine, New York, New York, USA.
authors.forename: Fatima A
authors.initials: FA
authors.lastname: Sehba
authors.forename: Igor
authors.initials: I
authors.lastname: Chereshnev
authors.forename: Saul
authors.initials: S
authors.lastname: Maayani
authors.forename: Victor
authors.initials: V
authors.lastname: Friedrich
authors.forename: Joshua B
authors.initials: JB
authors.lastname: Bederson
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology* / Q000473:pathology; D002545:Brain Ischemia / Q000201:enzymology / Q000473:pathology; D002452:Cell Count; D007124:Immunoenzyme Techniques; D007700:Kinetics; D008297:Male; D009474:Neurons / Q000201:enzymology / Q000473:pathology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000502:physiology*; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D013345:Subarachnoid Hemorrhage / Q000201:enzymology* / Q000473:pathology
chemical_list: D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; C496322:Nos1 protein, rat