Objective To explore the effect of ischaemic preconditioning (IPC) on ischaemic-reperfused (I/R) myocardium of elderly rat.
Methods 56 male Wistar rats were divided into seven groups of eight rats each: adult control group, adult I/R group, adult IPC group, elderly control group, elderly I/R group, elderly IPC group and elderly enhanced IPC group.
The Langendorff isolated heart perfusion models were established. The control group had a 90-min perfusion without any intervention. The I/R group had a 30-min equilibration period and a 30-min ischaemia and a 30-min reperfusion. The IPC group had a 10-min equilibration, then was elicited by two cycles of 5 min of ischaemia interspersed with 5 min reperfusion prior to 30 min ischaemia and a 30-min reperfusion. The enhanced IPC group had a 10-min equilibration, then was elicited by four cycles of 5 min of ischaemia interspersed with 5 min reperfusion prior to 30 min ischaemia and a 30-min reperfusion. The recovery rate of the left ventricular function, such as cardic output (CO), left ventricular developed pressure (LVDP), the maximum change rate of left ventricular pressure rise and fall (±dp/dtmax) were recorded. The activity of creatine kinase (CK) in coronary outflow, the activity of malonyldialdehyde (MDA) and superoxide dismutase (SOD) in myocardium were dectected. The percentage of necrotic area were observed.
Results In adult rats, the content of CK (89.48±18.72 U/l vs 115.76±16.72U/l, p<0.01) and MDA (9.53±3.44 nmol/mg vs 16.84±2.29 nmol/mg, p<0.01) were significantly less in IPC group than those in I/R group. In IPC group, the activity of SOD (584.7±122.62 U/mg vs 429.46±85.24 U/mg), the recovery rate of the left ventricular function, including CO, LVDP and±dp/dtmax, were much higher than those in I/R group (78.69±9.68% vs 65.10±8.63%, 83.61±8.46% vs 67.23±8.68%, 81.68±8.68% vs 67.89±6.89%, 89.79±7.78% vs 66.79±8.46%, p<0.01). And the percentage of necrotic area were lower in adult IPC group than in I/R group (5.25±4.33 vs 14.75±8.02, p<0.01). But there were no significant changes between IPC group and I/R group in elderly rats (p>0.05). However, there were great significant changes between enhanced IPC group and IR group in elderly rats, the content of CK (88.60±28.32 U/l vs 105.76±9.64 U/l, p<0.01) and MDA (8.38±3.36 nmol/mg vs 16.80±3.06 nmol/mg, p<0.05), the activity of SOD (558.87±78.66 U/mg vs 433.75±86.65 U/mg, p<0.01), the recovery rate of the left ventricular function, such as CO, LVDP and±dp/dtmax, were much higher than those in I/R group (77.99±10.02% vs 66.26±9.78%, 85.59±6.67% vs 73.90±6.66%, 83.87±9.98% vs 68.90±8.68%, 86.01±7.66% vs 70.39±7.98%, p<0.01). The percentage of necrotic area were lower in elderly IPC group than in I/R group (7.95±6.32% vs 15.68±10.36%, p<0.01).
Conclusion The effect of IPC on ischaemic reperfused myocardium of elderly rats was weaken. Prolonged ischaemia was able to resume the protective effect of IPC on elderly rat hearts.
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