4.6 Article

Cardioprotection by postconditioning in conscious rats is limited to coronary occlusions <45 min

出版社

AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpheart.00479.2006

关键词

myocardium; ischemia; infarct size; preconditioning

资金

  1. NHLBI NIH HHS [R01-HL-76794, R01-HL-74351, R01-HL-78825, R01 HL068088, R01-HL-55757, R37 HL055757, R01 HL076794, R01 HL055757, R01 HL070897, R01-HL-68088, P01 HL078825, R01-HL-70897, R01 HL074351] Funding Source: Medline

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Objectives: Brief episodes of ischemia and reperfusion after a lethal ischemic insult confer cardioprotection, a phenomenon termed ischemic postconditioning. However, all studies reported to date have been conducted in open-chest animal models. We sought to determine whether postconditioning occurs in conscious animals and whether it protects against severe myocardial injury. Methods: Chronically instrumented rats were assigned to a 30- (Subset 1), 45- (Subset 2), or 60-min (Subset 3) coronary occlusion followed by 24 h of reperfusion. In each subset, rats received no further intervention (control), were preconditioned with 12 cycles of 2-min occlusion/2-min reperfusion immediately (early preconditioning; EPC) or 24 h (late preconditioning; LPC) before myocardial infarction, or were postconditioned with 20 cycles of 10-s occlusion/10-s reperfusion immediately after myocardial infarction (20-10 PostC). Results: With a 30-min occlusion, infarct size (54.4 +/- 2.3% of risk region in control-30) was significantly reduced in EPC-30, LPC-30, and 20-10 PostC-30 groups (by 72, 70, and 47%, respectively; all P < 0.05 vs. control-30). With a 45-min occlusion, infarct size (62.2 +/- 2.4% in control-45) was reduced in EPC-45 and LPC-45 groups (by 47 and 41%, respectively; all P < 0.05 vs. control-45) but not in the 20-10 PostC-45 group [55.4 +/- 2.3%, P = not significant (NS) vs. control-45]. With a 60-min occlusion, infarct size (72.7 +/- 2.2% in control-60) was reduced in the EPC-60 (by 20%, P < 0.05) but not in the LPC-60 (63.6 +/- 2.5%, P = NS) or in the 20-20 PostC group (71.5 +/- 3.4%, P = NS). Conclusions: Both early and late ischemic preconditioning as well as ischemic postconditioning confer protection in conscious rats; however, unlike early preconditioning, postconditioning protects only against coronary occlusions < 45 min. In the conscious rat, the cardioprotection afforded by postconditioning is limited to mild to moderate myocardial injury.

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