The effect of uni-axial cyclic mechanical stretch on the expression of the adhesion protein integrin was investigated. Human umbilical endothelial cells (HUVECs) cultured an fibronectin coated silicon membranes were subjected to uni-axial cyclic stretch, The level of expression of integrin beta(3) mRNA was found to be increased and peaked at 4 hours in response to cyclic stretch using a semiquantitative RT-PCR method. The increased level of the integrin mRNA from stretched HUVECs remained higher than that ii om non-stretched controls. The amount of integrin beta(3) also increased and peaked at 12 hr, Immuno-fluorescent microscopy revealed that the amount of integrin beta(3) adhesions increased in stretched HUVECs compared with that in non-stretched HUVECs. These results suggest that uni-axial cyclic stretch up-regulates the expression of integrin beta(3). This increase in integrin beta(3), may enhance the adhesiveness to the substratum and contribute to the protection of HUVECs against being peeled off from the vessel wall. (C) 1997 Academic Press.