Abstract
Purpose: Protective effect of preconditioning (PR) and postconditioning (PT) for cardiac hypoxia-reoxygenation was examined. Methods: Hearts from male SD rat were Langendorff perfused and were made hypoxic for 30 min and reoxygenated for 30 min. PR was 3 times 5 min ischemia-3 min reperfusion cycle before hypoxia. PT was 3 times 30 sec ischemia-30 sec reperfusion cycle before reoxygenation. PR+PT group recieved both protocols. LV developed pressure (LVDP) and heart rate (HR) were monitored and as an index of irreversible damages, GOT release was quantified. Results: The recovery of pressure rate product (PRP; LVDP×HR) by reoxygenation was 19.7±4.6% in control group (CT) at 5 min. The recovery was significantly facilitated in PR and PT; PRP reached 33.0±10.2 and 41.0±7.5%, respectively at 5 min. PR+PT showed further quick recovery reaching 46.8±5.9% at 5 min. The recovery of PRP at 30 min reoxygenation in CT was 57.5±2.3%, while it recovered to 67.1±5.3% in PR and 63.9±4.4% in PT. However, in PR+PT, it remained 49.7±6.1%. GOT release (IU/min/g) at 2 min reoxygenation was 1.52±0.15 in CT. In PR (1.04±0.26) and PR+PT (1.15±0.14), increase in GOT was significantly (P<0.05) suppressed but there was no significant difference between PT (1.64±0.30) and CT. Conclusions: Either ischemic PR or PT showed cardiac protection against hypoxia-reoxygenation. However, in PR+PT group, protective effect disappeared. These results suggest that the mechanism of protection by PT is differ from that of PR, and their protective effects would be inhibited by each other. [Jpn J Physiol 54 Suppl:S96 (2004)]
