We examined the role of the sarcolemmal and mitochondrial
ATP-sensitive
potassium (K(
ATP)) channel in a rat model of
myocardial infarction after stimulation with the selective delta(1)-opioid receptor agonist
TAN-67. Hearts were subjected to 30 min of regional
ischemia and 2 h of reperfusion.
Infarct size was expressed as a percentage of the area at risk.
TAN-67 significantly reduced
infarct size/area at risk (29.6 +/- 3.3) versus control (63. 1 +/- 2.3). The sarcolemmal-selective K(
ATP) channel antagonist
HMR 1098, administered 10 min before
TAN-67, did not significantly attenuate cardioprotection (26.0 +/- 7.3) at a dose (3 mg/kg) that had no effect in the absence of
TAN-67 (56.3 +/- 4.3). Pretreatment with the mitochondrial selective antagonist
5-hydroxydecanoic acid (5-HD) 5 min before the 30-min occlusion completely abolished TAN-67-induced cardioprotection (54.3 +/- 2.7), but had no effect in the absence of
TAN-67 (62.6 +/- 4.1), suggesting the involvement of the
mitochondrial K(ATP) channel. Additionally, we examined the antiarrhythmic effects of
TAN-67 in the presence or absence of 5-HD and
HMR 1098 during 30 min of
ischemia. Control animals had an average
arrhythmia score of 10.40 +/- 2.41.
TAN-67 significantly reduced the
arrhythmia score during 30 min of
ischemia (2.38 +/- 0. 85). 5-HD and
HMR 1098 in the absence of
TAN-67 produced an insignificant decrease in the
arrhythmia score (8.80 +/- 2.56 and 4. 20 +/- 1.07, respectively). 5-HD administration before
TAN-67 treatment abolished its antiarrhythmic effect (4.71 +/- 1.11). However,
HMR 1098 did not abolish TAN-67-induced protection against arrhythmias (1.67 +/- 0.80). These data suggest that delta(1)-opioid receptor stimulation is cardioprotective against
myocardial ischemia and sublethal arrhythmias and suggest a role for the
mitochondrial K(ATP) channel in mediating these cardioprotective effects.