Abstract: AIM:To investigate the effects of different doses of aspirin on angiogenic functions of rat myocardial microvascular endothelial cells (CMECs) and the possible mechanism. METHODS: CMECs were isolated from rats with collagenase digestion and cultured with different doses of aspirin (1, 10, 100, 1 000, 5 000 μmol/L) in vitro. The proliferation of CMECs was analyzed by CCK-8 assay. Apoptotic cells of CMECs were detected by TUNEL. Migration of CMECs was assessed by migration assays. The angiogenic activity of CMECs was examined by tube formation experiment. pAKT protein expression was measured by Western blotting analysis, and FN protein expression was measured by ELISA analysis. RESULTS: Aspirin enhanced CMEC proliferation and pAKT protein expression and induced cell apoptosis at concentrations between 1 000 and 5 000 μmol/L. Aspirin promoted CMEC migration and angiogenesis at concentrations between 10 and 100 μmol/L, and FN protein expression increased with the increasing concentrations of aspirin. CONCLUSION: Low concentrations of aspirin (1-100 μmol/L) exert no obvious effect on the survival of CMECs, whereas high concentrations of aspirin (1 000-5 000 μmol/L) inhibit the proliferation of CMECs, reduce AKT phosphorylation levels and increase apoptosis. At low concentrations of aspirin (1-100 μmol/L), CMEC migration and tube formation are promoted possibly because aspirin, as a ring oxidase (COX) inhibitor, reduces the generation of PGI2 and increases FN expression.