Aim To investigate the expression of pregnancy associate plasma protein-A(PAPP-A) in coronary artery of patients with acute coronary syndrome(ACS) and fix PAPP-A masculine location by labelling smooth muscle cell.Methods There were 15 autopsiced cases which were consistent with the judge standard of ACS.18 coronary artery autopsiced cases without myocardial infarction and 17 coronary artery autopsiced cases with old myocardial infarction were chosen as control groups.Sequence section of the right,left coronary artery was made from beginning to the ending with an interval about 1 cm.The coronary artery degrees of stenosis of ACS group were measured and calculated with elastic fibers stain and NIH Scion Image analytical system.The arteries of ACS group were divided into 4 subgroups according to the degree of stenosis(<25% group,25%～50% group,50%～75% group and >75% group).Immunohistochemistry was used to detect the presence of smooth muscle cell and to examine the expression of PAPP-A.Results In ACS group,the PAPP-A rate of masculine in coronary artery smooth muscle of different degrees of stenosis subgroup were 93.3%,74.5%,78.3% and 50.0%.In ACS group,the expression of PAPP-A was found strongly in rupture area and endothelial cells which were remnant in ruptured plaque and adjacent coronary artery.PAPP-A expression in coronary artery showed a tendency to decrease with degree of stenosis increasing.The PAPP-A rate of masculine of ACS group was 80.4%,no myocardial infarction group was 66.9%,old myocardial infarction group was 56.8%.PAPP-A was more detectable in ACS group than in the other two groups.Conclusions PAPP-A are involved in the occurrence of ACS.In coronary artery the expression of PAPP-A has no definite relevance to the degree of stenosis.PAPP-A expression in coronary artery showed a tendency to decrease with degree of stenosis increasing.