Abstract: Objective　To observe activating protein-1(AP-1) members in response to changes ofwall-shear stress in osteoblas- tic cellsin vitro.Methods　Isolated and purified osteoblastic cells from the calvaria of newborn SD rats were cultured and sub- cultured. The third generation cellswere subjected towall-shear stress of 0.8 Pa,1.2 Pa,1.4 Pa and 1.6 Pa separately. Gene ex- pression of the seven AP-1 members were studied before (0 h) and 10 min,15 min,30 min,60 min after treated with wall-shear stress.Results　The expression of FosB,c-Fos, c-Jun,JunD and JunB mRNA increased transiently after application of 1.2 Pa wall-shear stress in osteoblastic cells compared to 0.8 Pa ,1.4 Pa and 1.6 Pa stress, and peaked at 15 min.Conclusion　Me- chanical environment changes in osteoblastic cells induced a dramatic induction of most of the AP-1 members.

Key words: wall-shear stress, osteoblastic cells, activating protein-1