Nitroglycerin induces late preconditioning against arrhythmias but not stunning in conscious sheep.
OBJECTIVE
Nitroglycerin, a nitric oxide donor, induces late preconditioning against stunning by short ischemia-reperfusion periods. The study purpose was to assess similar nitroglycerin protection against stunning and arrhythmias produced by prolonged reversible ischemia.


METHODS
Four groups of conscious sheep were studied, control: 12 minutes ischemia and 2 hour reperfusion; late preconditioning: six periods of 5 min ischemia-5 min reperfusion 24 h before 12 min ischemia and late preconditioning with 120 microg/kg and 600 microg/kg nitroglycerin administered instead of the ischemia-reperfusion periods.


RESULTS
Although late preconditioning protected against stunning (mean postischemic recovery of wall thickening fraction, control (n=10): 54.8+/-3.2, late preconditioning (n=9): 74.4+/-3.0, p<0.01), nitroglycerin 120 microg/kg (n=6) did not reproduce mechanical protection (50.1+/-3.8), even with a higher concentration of 600 microg/kg (59.1+/-3.7, n=4). However, nitroglycerin decreased arrhythmia severity index (control: 2.3+/-0.6, late preconditioning: 0.5+/-0.4, nitroglycerin 120 microg/kg: 1+/-0.4 and 600 microg/kg: 0.1+/-0.1 (p<0.05 vs. control).


CONCLUSIONS
Nitroglycerin only has a limited late preconditioning protective effect in conscious animals submitted to a reversible prolonged ischemia since it protects against arrhythmias but not against stunning.
Lascano
Elena C
EC
Department of Physiology, Pharmacology and Biochemistry, Favaloro University, Buenos Aires, Argentina. lascano@favaloro.edu.ar
Valle
Héctor F Del
HF
Negroni
Jorge A
JA
D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001145:Arrhythmias, Cardiac / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D003243:Consciousness; D003326:Coronary Circulation / Q000187:drug effects; D004195:Disease Models, Animal; D006339:Heart Rate / Q000187:drug effects; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D017202:Myocardial Ischemia / Q000150:complications* / Q000503:physiopathology; D017682:Myocardial Stunning / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D020030:Nitric Oxide Donors / Q000494:pharmacology* / Q000627:therapeutic use; D005996:Nitroglycerin / Q000494:pharmacology* / Q000627:therapeutic use; D012756:Sheep; D013997:Time Factors; D014665:Vasodilator Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017725:Ventricular Pressure / Q000187:drug effects
D000889:Anti-Arrhythmia Agents; D020030:Nitric Oxide Donors; D014665:Vasodilator Agents; D005996:Nitroglycerin