Background:Plasma transfusion is a common clinical practice.Remote ischemic preconditioning (RIPC) protects organs against ischemia-reperfusion (IR) injury.Whether preconditioned plasma (PP),collected at late phase after RIPC,could protect organs against IR injury in vivo is unknown.This study explored whether transfusion of PP could reduce myocardial infarct size (IS) after IR in rat in vivo.Methods:Eighty Lewis rats were randomized to eight groups (n =10 for each group).Two groups of plasma donor rats donated plasma at 48 h after transient limb ischemia (PP) or control protocol (nonpreconditioned plasma [NPP]).Six groups of recipient rats received normal saline (NS;NS-IR 1,and NS-IR 24 groups),NPP (NPP-IR 1 and NPP-IR 24 groups),or PP (PP-IR 1 and PP-IR 24 groups) at one or 24 h before myocardial IR.Myocardial IR consisted of 30-min left anterior descending (LAD) coronary artery occlusion and 180-min reperfusion.The area at risk (AAR) and infarct area were determined by double-staining with Evans blue and triphenyltetrazolium chloride.IS was calculated by infarct area divided by AAR.This was a 3 × 2 factorial design study,and factorial analysis was used to evaluate the data.If an interaction between the fluid and transfusion time existed,one-way analysis of variance with Bonferroni correction for multiple comparisons was used to analyze the single effects of fluid type when the transfusion time was fixed.Results:IS in the NPP-IR 1 and PP-IR 1 groups was smaller than in the NS-IR 1 group (F =6.838,P =0.005;NPP-IR 1:57 ± 8％ vs.NS-IR1:68 ± 6％,t =2.843,P =0.020;PP-IR 1:56 ± 8％ vs.NS-IR 1:68 ± 6％,t =3.102,P =0.009),but no significant difference was detected between the NPP-IR 1 and PP-IR 1 groups (57 ± 8％ vs.56 ± 8％,t =0.069,P =1.000).IS in the NPP-IR 24 and PP-IR 24 groups was smaller than in the NS-IR 24 group (F =24.796,P ＜ 0.001;NPP-IR 24:56％ ± 7％ vs.NS-IR 24:68 ± 7％,t =3.102,P =0.026;PP-IR 24:40 ± 9％ vs.NS-IR 24:68 ± 7％,t =7.237,P ＜ 0.001);IS in the PP-IR 24 group was smaller than in the NPP-IR 24 group (40 ± 9％ vs.56 ± 7％,t =4.135,P =0.002).Conclusion:Transfusion of PP collected at late phase after remote ischemic preconditioning could reduce IS,suggesting that late-phase cardioprotection was transferable in vivo.