Ischemia followed by reperfusion results in impairment of cellular and mitochondrial functionality due to opening of mitochondrial permeability transition pores. On the other hand, activation of mitochondrial
ATP-sensitive K(+) channels (
mitoK(ATP)) protects the heart against ischemic damage. This study examined the effects of
mitoK(ATP) and mitochondrial permeability transition on isolated rat heart mitochondria and cardiac cells submitted to simulated
ischemia and reperfusion (
cyanide/aglycemia). Both
mitoK(ATP) opening, using
diazoxide, and the prevention of mitochondrial permeability transition, using
cyclosporin A, protected against cellular damage, without additive effects.
MitoK(ATP) opening in isolated rat heart mitochondria slightly decreased Ca(2+) uptake and prevented mitochondrial
reactive oxygen species production, most notably in the presence of added Ca(2+). In ischemic cells,
diazoxide decreased ROS generation during
cyanide/aglycemia while
cyclosporin A prevented oxidative stress only during simulated reperfusion. Collectively, these studies indicate that opening
mitoK(ATP) prevents cellular death under conditions of
ischemia/reperfusion by decreasing mitochondrial
reactive oxygen species release secondary to Ca(2+) uptake, inhibiting mitochondrial permeability transition.