Myocardial ischemia-reperfusion (I/R) injury induces endothelial glycocalyx (GCX) degradation. Several candidate GCX-protective factors including albumin have been identified, few have been demonstrated in in vivo studies and most albumins used to date have been heterologous. Albumin is a carrier protein for sphingosine 1-phosphate (S1P), which has protective effects on the cardiovascular system. However, changes inhibited by albumin in the endothelial GCX structure in I/R in vivo via the S1P receptor has not been reported. In this study, we aimed to determine whether albumin prevents the shedding of endothelial GCX in response to I/R in vivo. Rats were divided into four groups: control (CON), I/R, I/R with albumin preload (I/R + ALB), and I/R + ALB with S1P receptor agonist fingolimod (I/R + ALB + FIN). FIN acts as an initial agonist of S1P receptor 1 and downregulates the receptor in an inhibitory manner. The CON and I/R groups received saline and I/R + ALB and I/R + ALB + FIN groups received albumin solution before left anterior descending coronary artery ligation. Our study used rat albumin. Shedding of endothelial GCX was evaluated in the myocardium by electron microscopy, and the concentration of serum syndecan-1 was measured. Thus, albumin administration maintained the structure of endothelial GCX and prevented shedding of endothelial GCX via the S1P receptor in myocardial I/R, and FIN annihilated the protective effect of albumin against I/R injury. • Albumin have been identified as a candidate protective factor for endothelial glycocalyx, few have been demonstrated in in vivo studies and most albumins used to date have been heterologous. • Albumin is a carrier protein for sphingosine 1-phosphate, which has protective effects on the cardiovascular system. • The protection effect by albumin in the glycocalyx in ischemia/reperfusion injury in vivo via the S1P receptor has not been reported. • In this study, we aimed to determine whether homologous albumin prevents the shedding of endothelial GCX in response to ischemia/reperfusion in vivo. • Albumin prevented shedding of endothelial GCX via the S1P receptor in myocardial ischemia/reperfusion. [ABSTRACT FROM AUTHOR]