Effect of long-term shear stress exposure on calcium response and morphology of cultured endothelial cells

Endothelial cells (ECs) that line the inner surface of blood vessels are continuously exposed to shear stress induced by blood flow, in vivo, and shear stress affects the intracellular calcium ([Ca²⁺]1), which initiates cellular responses. Although shear-stress induced [Ca²⁺]1 responses shortly (within 10 min after initiation of flow have been studied, the effects of long-term exposure (24 hr) of shear stress on [Ca²⁺]1 responses have not. Here, we studied the effect of long-term exposure of shear stress on [Ca²⁺]1 responses in cultured ECs by using a confocal laser microscope and calcium indicator (Calcium Green-1/ AM). At the initiation of shear stress of 2 Pa (0 hr), 27% of the cells exhibited [Ca²⁺]1 responses. This percentage gradually decreased with increasing exposure time, reaching about 4% after 24 hr of exposure. These data indicate that long-term shear-stress exposure affects [Ca²⁺]1 responses in cultured ECs.