Role of endothelial nitric oxide synthase as a trigger and mediator of isoflurane-induced delayed preconditioning in rabbit myocardium.
BACKGROUND
Isoflurane produces delayed preconditioning in vivo. The authors tested the hypothesis that endothelial, inducible, or neuronal nitric oxide synthase (NOS) is a trigger or mediator of this protective effect.


METHODS
In the absence or presence of exposure to isoflurane (1.0 minimum alveolar concentration) 24 h before experimentation, pentobarbital-anesthetized rabbits (n = 128) instrumented for hemodynamic measurement received 0.9% saline (control), the nonselective NOS inhibitor N-nitro-l-arginine methyl ester (10 mg/kg), one of two of the selective inducible NOS antagonists aminoguanidine (300 mg/kg) or 1400W (0.5 mg/kg), or the selective neuronal NOS inhibitor 7-nitroindazole (50 mg/kg) administered before exposure to isoflurane (trigger; day 1) or left anterior descending coronary artery occlusion (mediator; day 2). All rabbits underwent 30 min of coronary occlusion followed by 3 h of reperfusion. Tissue samples for reverse-transcription polymerase chain reaction and immunohistochemistry were also obtained in the presence or absence of N-nitro-l-arginine methyl ester with or without isoflurane pretreatment.


RESULTS
Isoflurane significantly (P < 0.05) reduced infarct size (23 +/- 5% [mean +/- SD] of the left ventricular area at risk; triphenyltetrazolium chloride staining) as compared with control (42 +/- 7%). N-nitro-l-arginine methyl ester administered before isoflurane or coronary occlusion abolished protection (49 +/- 7 and 43 +/- 10%, respectively). Aminoguanidine, 1400W, and 7-nitroindazole did not alter infarct size or affect isoflurane-induced delayed preconditioning. Isoflurane increased endothelial but not inducible NOS messenger RNA transcription and protein translation immediately and 24 h after administration of the volatile agent. Pretreatment with N-nitro-l-arginine methyl ester attenuated isoflurane-induced increases in endothelial NOS expression.


CONCLUSIONS
The results suggest that endothelial NOS but not inducible or neuronal NOS is a trigger and mediator of delayed preconditioning by isoflurane in vivo.
Chiari
Pascal C
PC
Division of Cardiovascular Diseases, Department of Anesthesiology, the Medical College of Wisconsin, Milwaukee 53226, USA.
Bienengraeber
Martin W
MW
Weihrauch
Dorothee
D
Krolikowski
John G
JG
Kersten
Judy R
JR
Warltier
David C
DC
Pagel
Paul S
PS
D000818:Animals; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D007530:Isoflurane / Q000494:pharmacology* / Q000627:therapeutic use; D008297:Male; D009203:Myocardial Infarction / Q000201:enzymology / Q000517:prevention & control; D009206:Myocardium / Q000201:enzymology*; D019001:Nitric Oxide Synthase / Q000502:physiology*; D052250:Nitric Oxide Synthase Type III; D011817:Rabbits
D007530:Isoflurane; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III