COMPARISON OF ISCHEMIC PRECONDITIONING IN BLOOD PERFUSED AND BUFFER PERFUSED ISOLATED HEART MODELS

Objective: The aim was to compare the effects of ischaemic preconditio ning in the buffer perfused and parabiotic blood perfused Langendorff rabbit heart models. Methods: Isolated hearts were perfused with eithe r Krebs-Henseleit buffer solution or blood from a support rabbit. Hear ts were subjected to an initial 30 min stabilisation period followed b y 30 min of global ischaemia and 60 min of reperfusion. Ischaemic prec onditioned (IP) hearts were also subjected to one cycle of 5 min globa l ischaemia and 10 min of reperfusion before the 30 min ischaemia. For each experiment, left ventricular function and necrosis were measured . Results: Necrosis, as measured by tetrazolium staining and expressed as a percentage of the left ventricular area, was significantly diffe rent between the buffer perfused control [42.5%(SEM 6.9), n=7] and buf fer 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 reducti on in necrosis produced by ischaemic preconditioning was not significa ntly 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 re perfusion period. In buffer perfused hearts, left ventricular end dias tolic pressure at 60 min reperfusion was not significantly different b etween the IP and the control groups, at 34.3(5.5) mm Hg v 37.8(4.9) m m Hg, respectively. Similarly, there was no statistically significant difference in left ventricular end diastolic pressure in the blood per fused groups at this time: 13.3(2.8) in the IP group v 24.0(6.5) in co ntrols. Conclusions: In isolated heart models of global ischaemia and reperfusion. in which both recovery of function and necrosis were asse ssed together, ischaemic preconditioning was highly effective in reduc ing necrosis in both blood perfused and buffer perfused models. Howeve r, ischaemic preconditioning did not significantly improve postischaem ic recovery of function in either of the two preparations.