Objective To investigate the molecular mechanism of atherosclerosis that related to age. Methods Immunohistochemistry staining and Western blot were adopted to determine the nuclear translocation of nuclear factor-kappa B （NF-κB） and expression of platelet-derived growth factor B （PDGF-B） in smooth muscle cells （SMCs） co-cultured with low density lipoprotein （LDL）

oxidized LDL （ox-LDL）

and ox-LDL+high density lipoprotein （HDL） originated from rats of 2 and 10 months old respectively. Fat stain was used to identify the lipid intake in SMCs. Results The optimal stimulation time of ox-LDL to SMCs was 12 hours. NF-κB intensity increased in most nuclei of SMCs that originated from rats of either 2 or 10 months old co-cultured with ox-LDL. The intensity of NF-κB and the amount of intracellular lipid taken in SMCs were more obvious in cells from 10-month-old rats than from the younger ones. Change of PDGF-B expression in SMCs was not remarkable in each group of rats. Conclusions The 10-month-old rats are more susceptive to ox-LDL than 2-month-old rats in activating nuclear transloca- tion of NF-κB. Maybe this is one of the important reasons contributing to the difference between the older and younger rats on the initiation and development of atherosclerosis lesion. Expression of PDGF-B is not associated with the activity of nuclear translocation of NF-κB.