Reperfusion after brief repetitive ischemia in porcine myocardium does not alter expression of creatine kinase MM or mitochondrial ATPase mRNAs

We examined whether the mRNA expression of creatine kinase MM isozyme (CKMM) and mitochondrial F1-ATPase, the key enzymes of intracellular energy transduction, are altered in porcine myocardium subjected to repeated brief periods of ischemia followed by reperfusion. The left anterior descending coronary artery was occluded for two cycles of 10 min with 30 min reperfusion in between, followed by the reperfusion up to 210 min. Systolic wall thickening was significantly decreased at 30 min reperfusion after both occlusions and remained depressed during reperfusion. In Northern blot analysis 1.5 kb CKMM and 1.9 F1-ATPase mRNA species were detected in sham, nonischemic and ischemic myocardial tissues. Densitometric analysis of signals showed a 30% decrease of the CKMM mRNA expression (p < 0.05 as compared to nonischemic area of the same heart and sham operated animals) only during the first period of ischemia. Reperfusion as well as the subsequent period of ischemia did not alter expression of CKMM mRNA. The expression of F1-ATPase mRNA remained unchanged during ischemia and reperfusion. We conclude that reperfusion after brief myocardial ischemia in swine is not associated with changes in CKMM and F1-ATPase mRNA expression. Our findings would support the hypothesis that myocardial stunning is not caused by altered expression of energy transducing enzymes.