Background Study of the relationship between mast cells and atherosclerosis is mostly dependent on pathological observation and cytology experiments. To investigate the effects of mast cells degranulation on plaque and their possible mechanisms we used apolipoprotein E knockout mice which had been placed perivascular common carotid collar with mast cells degranulator compound 48-80.Methods Forty apolipoprotein E knockout mice were fed a western-type diet and operated on with placement of perivascular right common carotid collar. Four weeks after surgery, the mice were intraperitoneally injected with compound 48-80 (0.5 mg/kg) or D-Hanks every other day for 4 times. The serum lipids and activity of tryptase were measured. Tissue sections were stained with hematoxylin and eosin. Corresponding sections were stained with toluidine blue and immunohistochemically with antibodies against macrophage-specific antigen, α-smooth muscle actin, interleukin-1β and van Willebrand factor. Simultaneously, basic fibroblast growth factor was detected by in situ hybridization and immunofluorescence.Results No pathological change was observed in common carotid non-collar placement but atherogenesis in common carotid collar placement of both groups. There was a significant increase in plaque area ((5.85±0.75)×104 vs (0.86±0.28)×104 μm2, P