title: Regulation of inducible nitric oxide synthase in ischemic preconditioning of muscle flap in a rat model.
abstract: OBJECTIVE
  Ischemic preconditioning has been shown to influence flap tolerance to prolonged ischemia. Nitric oxide (NO) synthesis is one of the proposed mechanisms involved in ischemic preconditioning. In this study, the molecular marker of NO is examined in correlation with ischemic preconditioning on improving muscle flap survival.
  
  
  METHODS
  Fifty male Sprague-Dawley rats were randomized into experimental and control groups. The gracilis muscle flap with femoral vascular pedicle was used as a flap model. Ischemic preconditioning consisted of 3 sequences of clamping the pedicle for 10 minutes followed by 10 minutes of reperfusion for a total of 1 hour. In part I, the experimental group (n = 10) underwent ischemic preconditioning for 1 hour. In the control group (n = 10), the flaps were dissected without clamping of the pedicle. Both groups were then subjected to 4 hours of global ischemia by continuous pedicle clamping, after which the flaps were sutured to their beds. On postoperative day 3, flap survival was determined by gross and histologic examinations. The evaluators were blinded to the treatment. In part II, the experimental group (n = 12) underwent ischemic preconditioning, while the control group (n = 12) did not. The flaps from each group were harvested for inducible nitric oxide synthase (iNOS) gene expression using reverse transcriptase-polymerase chain reaction at the end of 1 hour after reperfusion and at 4 hours of global ischemia.
  
  
  RESULTS
  The results indicated a significantly higher survival rate in the experimental group than in the control group (90 versus 50%, P < 0.05). iNOS gene expression was significantly higher in the experimental group than in the control group at 1 hour after ischemic preconditioning (0.73+/-0.18 versus 0.26+/-0.11, P < 0.01). However, after 4 hours of global ischemia, iNOS expression in the control group was statistically higher than in the experimental group (0.83+/-0.16 versus 0.26+/-0.07, P < 0.01).
  
  
  CONCLUSIONS
  We conclude that ischemic preconditioning can enhance flap tolerance to ischemia-reperfusion injury and improve flap viability rate. This study provides evidence that the regulation of NOS may play a role in ischemic preconditioning phenomenon and warrants further investigation.
authors.affiliation: Division of Plastic Surgery, University of Mississippi Medical Center, Jackson, 39216, USA. fzhang@surgery.umsmed.edu
authors.forename: Feng
authors.initials: F
authors.lastname: Zhang
authors.forename: Tanya
authors.initials: T
authors.lastname: Oswald
authors.forename: Jessica
authors.initials: J
authors.lastname: Holt
authors.forename: Jacob
authors.initials: J
authors.lastname: Gerzenshtein
authors.forename: Man-Ping
authors.initials: MP
authors.lastname: Lei
authors.forename: William C
authors.initials: WC
authors.lastname: Lineaweaver
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D016009:Chi-Square Distribution; D015870:Gene Expression; D019194:Ischemic Preconditioning; D008297:Male; D008833:Microcirculation; D018482:Muscle, Skeletal / Q000098:blood supply*; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013524:Surgical Flaps
chemical_list: D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat