Abstract 1938: Characterization of the Circulating Effector of Remote Ischemic Preconditioning
We have recently shown that remote ischemic preconditioning (rIPC), induced by repeated short periods of limb ischemia, reduces multi system injury in children undergoing cardiac surgery. The effector of rIPC is not known.
Methods: Using Langendorff preparation, 5 groups of rabbits were studied. Hearts were infused with Krebs solution and :
plasma from control donors;
plasma from donors subjected to rIPC;
dialysate from control plasma;
dialysate from rIPC plasma;
dialysate from rIPC hearts passed over a C18 column.
rIPC was induced by 4 cycles of 5 min limb ischemia and 5 min of reperfusion. In group1–2, 100mL of plasma was infused into heart with Krebs over 30 min prior to ischemia. In group 3–5, using a membrane with a 15 kDa cut-off, 100mL of plasma was dialysed against 1L Krebs; the dialysate was perfused for 30 min prior to ischemia. A C18 column was used to remove hydrophobic substances. All hearts were subjected to 30 min of LAD ischemia, followed by 120 min of reperfusion. The ratio of infarct size/area at risk was calculated. As confirmation of the humoral effect, and the absence of a neurogenic mechanism, the dialysate was tested in isolated fresh cardiomyocytes, in a previously described model with 45 min simulated ischemia/60 min reperfusion.
Results Figure 1⇓ summarizes the Langendorff studies (p > 0.05 = ns, one-way ANOVA). Using paired (n = 4) isolated cardiomyocytes treated with dialysate from rIPC or control plasma the % necrosis was 31.1 ± 1.9% (p < 0.003) and 52.5 ± 2.2%, respectively.
Conclusions: rIPC is mediated by a circulating hydrophobic factor, < 15kDa in size, that provides potent protection from myocardial I-R injury, in isolated whole hearts and cardiomyocytes.