title: Early preconditioning prevents the loss of endothelial nitric oxide synthase and enhances its activity in the ischemic/reperfused rat heart.
abstract: Cardiac ischemia may be responsible for either the loss of endothelial nitric oxide synthase (eNOS) or changes in its activity, both conditions leading to coronary dysfunction. We investigated whether early ischemic preconditioning was able to preserve eNOS protein expression and function in the ischemic/reperfused myocardium. Langendorff-perfused rat hearts were subjected to 20 min global ischemia, followed by 30 min reperfusion (I/R). A second group of hearts was treated as I/R, but preconditioned with three cycles of 5 min-ischemia/5 min-reperfusion (IP). Cardiac contractility markedly decreased in I/R, consistently with the rise of creatine kinase (CK) activity in the coronary effluent, whilst ischemic preconditioning significantly improved all functional parameters and reduced the release of CK. Western blot analysis revealed that the amount of eNOS protein decreased by 54.2% in I/R with respect to control (p < 0.01). On the other hand, NOS activity was not significantly reduced in I/R, as well as cGMP tissue levels, suggesting that a parallel compensatory stimulation of this enzymatic activity occurred during ischemia/reperfusion. Ischemic preconditioning completely prevented the loss of eNOS. Moreover, both NOS activity and cGMP tissue level were significantly higher (p < 0.05) in IP (12.7 +/- 0.93 pmol/min/mg prot and 58.1 +/- 12.2 fmol/mg prot, respectively) than I/R (7.34 +/- 2.01 pmol/min/mg prot and 21.4 +/- 4.13 fmol/mg prot, respectively). This suggest that early ischemic preconditioning may be useful to accelerate the complete recovery of endothelial function by preserving the level of cardiac eNOS and stimulating the basal production of nitric oxide.
authors.affiliation: Department of Biochemistry "G. Moruzzi", University of Bologna, Italy. claudio.muscari@unibo.it
authors.forename: Claudio
authors.initials: C
authors.lastname: Muscari
authors.forename: Francesca
authors.initials: F
authors.lastname: Bonafe'
authors.forename: Chiara
authors.initials: C
authors.lastname: Gamberini
authors.forename: Emanuele
authors.initials: E
authors.lastname: Giordano
authors.forename: Benedetta
authors.initials: B
authors.lastname: Tantini
authors.forename: Monia
authors.initials: M
authors.lastname: Fattori
authors.forename: Carlo
authors.initials: C
authors.lastname: Guarnieri
authors.forename: Claudio Marcello
authors.initials: CM
authors.lastname: Caldarera
mesh_terms: D000818:Animals; D015153:Blotting, Western; D003402:Creatine Kinase / Q000378:metabolism; D019157:Ischemic Preconditioning, Myocardial; D009200:Myocardial Contraction / Q000502:physiology; D017202:Myocardial Ischemia / Q000201:enzymology / Q000503:physiopathology*; D009206:Myocardium / Q000201:enzymology*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III; D051381:Rats
chemical_list: D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D003402:Creatine Kinase