RESUMO
OBJECTIVES: A reversible contractile dysfunction without necrosis after transient myocardial ischemia has been termed stunning. The molecular mechanisms underlying this phenomenon are only now beginning to be unraveled. It is conceivable that the expression of early-response genes may play a crucial role in stunning. METHODS: The expression of HSP-70, c-jun, and GRP-94 was investigated in a chronically instrumented dog model (n = 9). The left anterior descending coronary artery was occluded temporarily for 10 minutes after the animals had fully recovered from instrumentation. The wall thickening fraction was measured in the left anterior descending coronary artery and the nonischemic ramus circumflex of the left coronary artery-perfused region. When the wall thickening fraction of the left anterior descending coronary artery had recovered to 50% of preocclusion values, tissue samples were obtained from the areas perfused by the left anterior descending coronary artery and the nonischemic ramus circumflex of the left coronary artery. RESULTS: The messenger RNA of HSP-70 was increased to 214% +/- 26% in the area perfused by the left anterior descending artery compared with that perfused by the nonischemic ramus circumflex of the left coronary artery. There was no difference in the messenger RNA of GRP-94. The HSP-70 content was elevated to 130% +/- 14% in the left anterior descending artery compared with the area perfused by the ramus circumflex of the left coronary artery, and the c-jun protein content was 70% +/- 25% higher in the ischemic area compared with the control area. CONCLUSIONS: The induction of early-response genes observed here may indicate that they play an adaptive role in myocardial stunning, even in conscious mammals.
