2-Nicotinamidoethyl nitrale (2-NN) protects myocardium in ischemia and reperfusion via the protein kinase C pathway.
BACKGROUND
Several recent studies have suggested an ATP-sensitive potassium channel opener (2-nicotinamidoethyl nitrate: 2-NN) may exert a protective effect against the myocardial ischemic/reperfusion injury. This study examines the effects of 2-NN on intracellular signaling by measuring intracellular cyclic AMP, cyclic GMP accumulation and protein kinase C (PKC) activity after 2-NN perfusion.


METHODS
Ischemia/reperfused hearts were made by LAD occlusion for 30 min followed by 30 min of reperfusion in isolated rat hearts. Hearts were pre-perfused with 0.1 mM 2-NN, 100 nM Calphostin C, or 2-NN plus Calphostin C for 10 min prior to ischemia. The left ventricular function, cyclic AMP, cyclic GMP and LDH were examined to determine the effects of 2-NN on ischemic/reperfusion injury. Four separate groups of hearts were stained with a bisindolylmaleimide PKC inhibitor conjugated to fluorescein (fim, Teflabs) and PKC activity was measured.


RESULTS
2-NN reduced ischemia/reperfusion injury as evidenced by the enhanced myocardial functional recovery, decreased LDH release after reperfusion, and decreased reperfusion arrhythmias. The PKC inhibitor attenuated myocardial functional recovery but not reperfusion arrhythmias. Cyclic AMP levels decreased after 10 min of 2-NN perfusion, compared to controls. We observed an increase in PKC activity after 2-NN treatment.


CONCLUSIONS
These results suggest that PKC plays a significant role in the cardioprotective effect of 2-NN on ischemic and reperfused myocardium. The anti-arrhythmic effect of 2-NN in the reperfusion phase may be linked its action on the ATP-sensitive potassium channel itself rather than its effect on PKC activity.
Watanabe
M
M
Department of Thoracic and Cardiovascular Surgery, Tokyo Medical and Dental University, Tokyo, Japan. masa-cvs@hiroo-hospital.metro.tokyo.jp
Mizuno
T
T
Tanaka
H
H
Sakamoto
T
T
Sunamori
M
M
D000818:Animals; D003326:Coronary Circulation / Q000502:physiology*; D000242:Cyclic AMP / Q000032:analysis; D006152:Cyclic GMP / Q000032:analysis; D004195:Disease Models, Animal; D006334:Heart Function Tests; D006439:Hemodynamics / Q000502:physiology; D008297:Male; D008856:Microscopy, Fluorescence; D009200:Myocardial Contraction / Q000502:physiology; D017202:Myocardial Ischemia / Q000175:diagnosis / Q000188:drug therapy*; D015428:Myocardial Reperfusion Injury / Q000188:drug therapy* / Q000517:prevention & control; D009281:Naphthalenes / Q000494:pharmacology*; D020108:Nicorandil / Q000494:pharmacology*; D011336:Probability; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D012680:Sensitivity and Specificity
D009281:Naphthalenes; D020108:Nicorandil; D000242:Cyclic AMP; D006152:Cyclic GMP; C058819:calphostin C