Flow-induced calcium oscillations in rat osteoblasts are age, loading frequency, and shear stress dependent

Bone adaptation tomechanical loading is dependent on age and the frequency and magnitudeof loading. It is believed that load-induced fluid flow in the porousspaces of bone is an important signal that influences bone cellmetabolism and bone adaptation. We used fluid flow-induced shear stressas a mechanical stimulus to study intracellular calcium(Ca) signaling in rat osteoblastic cells (ROB)isolated from young, mature, and old animals. Fluid flow producedhigher magnitude and more abundant Ca²⁺]_ioscillations than spontaneous oscillations, suggesting that flow-induced Ca signaling encodes a differentcellular message than spontaneous oscillations. ROB from old ratsshowed less basal Ca²⁺]_i activity and wereless responsive to fluid flow. Cells were more responsive to 0.2 Hzthan to 1 or 2 Hz and to 2 Pa than to 1 Pa. These data suggest that thefrequency and magnitude of mechanical loading may be encoded by thepercentage of cells displaying Ca²⁺]_ioscillations but that the ability to transduce this information may bealtered with age.