Ischemic preconditioning may be transferable via whole blood transfusion: preliminary evidence

This research was designed to test the hypothesis that ischemic preconditioning can be transferred between animals via whole blood transfusion. Preconditioning at a distance refers to the reduction in myocardial infarct size seen when coronary artery occlusion is preceded by brief ischemic episodes of noncardiac tissue. Isolation of the trigger signal responsible for this effect may be useful in the diagnosis and treatment of acute coronary occlusive syndromes. Rabbits were paired by crossmatching blood samples prior to experimentation. Crossmatched pairs were placed into either preconditioned (P) or control sets. Rabbits in the preconditioned sets were further divided into donor (PD) and acceptor (PA) animals. PD animals underwent five episodes of circumflex and renal artery occlusion followed by reperfusion. Before and after each preconditioning episode, a whole blood exchange was performed between PD and PA animals. Alternatively, control rabbits underwent the same surgical procedures and time-sequenced transfusion without preconditioning. All animals then underwent prolonged circumflex occlusion (60 minutes) followed by reperfusion (30 minutes). The area of myocardium at risk (R) was determined by isotope-labeled microsphere injection. Infarct size (I) was determined by NBT staining. The percent infarct within the risk area (I/R) was then compared. The I/R was significantly lower in the PA (14.0% +/- 12.2) and PD (14.3% +/- 11.2) groups as compared with controls (61% +/- 20. 6). There was no significant difference between the tPA and TPD groups. In conclusion, the ischemic preconditioning effect can be transferred to nonpreconditioned animals via whole blood transfusion, suggesting a humoral mechanism for preconditioning at a distance.