Effects of fluid shear stress on bone cells.

Neonatal rat calvarial cells (osteoblast-enriched) were cultured in monolayer on glass slides and subjected to a step increase in shear stress ranging from 3 to 60 dyne/cm2 in a laminar flow chamber. The level of intracellular free calcium ion concentration was monitored using Fura-2 fluorescence during the application of stress. Application of a step increase in stress resulted in a transient increase in calcium starting about 10-20 s after turning on the pump, reaching a peak in about 35 s and declining thereafter, despite the continued shear stress, and reaching near baseline values in about 100 s. No change in cytoplasmic calcium was observed with a step increase in shear stress of 3 dyne/cm2. Between 6 dyne/cm2 and 60 dyne/cm2, the magnitude of the calcium response increased with the applied shear stress.