Effects of in vivo myocardial ischemia and reperfusion on interstitial nitric oxide metabolites.
BACKGROUND
There have been numerous studies examining the role of nitric oxide (NO) in myocardial ischemia-reperfusion injury; however, few studies have included measurements of NO or related reactive nitrogen species. The purpose of this study was to determine the effects of in vivo regional myocardial ischemia on interstitial fluid (ISF) reactive nitrogen species.


METHODS
Open chest pigs were submitted to one of three protocols: (1) 15 minutes coronary occlusion and 2 hours reperfusion, (2) 60 minutes coronary occlusion and 2 hours reperfusion, or (3) two-cycle ischemic preconditioning (IPC) followed by prolonged ischemia and 2 hours reperfusion. The stable NO metabolites, nitrite plus nitrate (NOx), in cardiac microdialysis samples were measured by ozone chemiluminescence.


RESULTS
NOx concentration decreased 40% +/- 6% (p < 0.05) during brief ischemia but returned to baseline during reperfusion. Dialysate NOx levels decreased further after 60 minutes ischemia (60% +/- 3% of baseline, p < 0.01) but reperfusion dialysate NOx concentration increased 34% +/- 9% above baseline (p < 0.05). Preconditioning did not increase dialysate NOx but did accelerate the ischemia-induced decrease in NOx levels (p < 0.05). Reperfusion NOx levels in preconditioned pigs were significantly lower than in nonpreconditioned pigs (p < 0.05).


CONCLUSIONS
These results suggest that ischemia is associated with decreased ISF NOx concentration. Reperfusion NOx levels are increased after prolonged ischemia, an effect that is significantly blunted by ischemic preconditioning.
Stevens
Randy M
RM
Department of Surgery, University of Kentucky College of Medicine, Lexington 40536-0298, USA.
Jahania
M Salik
MS
Stivers
Jennifer E
JE
Mentzer
Robert M
RM
Lasley
Robert D
RD
D000818:Animals; D005110:Extracellular Space / Q000737:chemistry*; D019157:Ischemic Preconditioning, Myocardial; D017551:Microdialysis; D017202:Myocardial Ischemia / Q000378:metabolism* / Q000503:physiopathology; D015425:Myocardial Reperfusion; D009206:Myocardium / Q000378:metabolism*; D009566:Nitrates / Q000032:analysis; D009569:Nitric Oxide / Q000032:analysis*; D009573:Nitrites / Q000032:analysis; D013552:Swine
D009566:Nitrates; D009573:Nitrites; D009569:Nitric Oxide