Comparison of ischaemic preconditioning in blood perfused and buffer perfused isolated heart models

The aim was to compare the effects of ischaemic preconditioning in the buffer perfused and parabiotic blood perfused Langendorff rabbit heart models.

Isolated hearts were perfused with either Krebs-Henseleit buffer solution or blood from a support rabbit. Hearts were subjected to an initial 30 min stabilisation period followed by 30 min of global ischaemia and 60 min of reperfusion. Ischaemic preconditioned (IP) hearts were also subjected to one cycle of 5 min global ischaemia and 10 min of reperfusion before the 30 min ischaemia. For each experiment, left ventricular function and necrosis were measured.

Necrosis, as measured by tetrazolium staining and expressed as a percentage of the left ventricular area, was significantly different between the buffer perfused control [42.5% (SEM 6.9), n = 7] and buffer perfused IP group [22.2% (5.4), n = 7, p < 0.01]. In the blood perfused experiments, the IP group also had less necrosis [9.3% (3.1), n = 9] as compared to controls [22.9%(4.2), n = 9, p < 0.01]. The percentage reduction in necrosis produced by ischaemic preconditioning was not significantly different between the buffer perfused and blood perfused models. Peak left ventricular systolic pressure was not different between the control and IP hearts in either model at any time during the 60 min reperfusion period. In buffer perfused hearts, left ventricular end diastolic pressure at 60 min reperfusion was not significantly different between the IP and the control groups, at 34.3(5.5) mm Hg v 37.8(4.9) mm Hg, respectively. Similarly, there was no statistically significant difference in left ventricular end diastolic pressure in the blood perfused groups at this time: 13.3(2.8) in the IP group v 24.0(6.5) in controls.

In isolated heart models of global ischaemia and reperfusion, in which both recovery of function and necrosis were assessed together, ischaemic preconditioning was highly effective in reducing necrosis in both blood perfused and buffer perfused models. However, ischaemic preconditioning did not significantly improve postischaemic recovery of function in either of the two preparations.