OBJECTIVES: While propranolol is known as an effective treatment for infantile hemangioma,little is known about the mechanism of its action.We hypothesized that propranolol may weaken mast cells function in the process of angiogenesis of hemangioma.METHODS: To test this hypothesis, the effect of propranolol on beta-receptors of HUVECs and HMC-1 were assessed, and propranolol on blood vessels formation and inflammation of HUVECs were detected.Then pre-treated HMC-1 with propranolol, the supernatant secretion was collected by HMC-1 and the supernatant was added to HUVECs.