Abstract： Objective To investigate the relationship between the left ventricular function and the expression of P-selectin in the serum and cardiac muscle in hemorrhagic shock resuscitation,and to evaluate the effects of L-arginine(L-Arg)against the harmful effect of P-selectin.Methods Thirty SD rats were randomly divided into 3 equal groups:hemorrhagic shock resuscitation(HS)group(undergoing bloodletting until the mean arterial pressure of 40 mm Hg and then re-infusion of the lost blood),L-Arg treatment group (undergoing bloodletting and then re-infusion with L-Arg simultaneously),and normal control(NC)group (undergoing infusion of normal saline).Cannulation was conducted via left carotid artery into the left ventricular to record left ventricular systolic pressure(LVSP),left ventricular end diastolic pressure (LVEDP),and left ventricular±dp/dtmax.Serum creatine kinase(CK)was detected by colorimetry.Three hours after the HS the rats were killed with samples of blood and apex of heart collected to detect the P-selectin expression by ELISA and immunohistochemistry.Microscopy was used to observe the expression of P-selectin in the vascular endothelial cells and cardiac muscle cells.Results The LVSP,maximal rate of LV pressure elevation(+dp/dtmax),and maximal rate of LV pressure depression(-dp/dtmax)of the HS and L-Arg groups were all significantly lower than those of the NC group(all P＜0.01).The LVEDP of the HS and L-Arg groups were all higher than that of the NC group(both P＜0.01).Three hours after resuscitation,the CK levels of the HS and L-Arg groups were significantly higher than that of the NC group (both P＜0.01),and that of the L-Arg groups was significantly lower than that of the HS group(P＜0.05),the P-selectin levels of the serum and cardiac muscle cells of the HS and L-Arg groups were all significantly higher than those of the NC group(both P＜0.01),and those of the L-Arg group were significantly lowcr than those of the HS group ( both P＜0.05).Conclusion After hemorrhagic shock and resuscitation P-selectin may play an important role in cardiac injury,L-Arg can inhibit the expression of Pseleetin,thus protecting the cardiac function against the harmful effect of P-selectin.