title: Flow-induced calcium oscillations in rat osteoblasts are age, loading frequency, and shear stress dependent.
abstract: Bone adaptation to mechanical loading is dependent on age and the frequency and magnitude of loading. It is believed that load-induced fluid flow in the porous spaces of bone is an important signal that influences bone cell metabolism and bone adaptation. We used fluid flow-induced shear stress as a mechanical stimulus to study intracellular calcium (Ca) signaling in rat osteoblastic cells (ROB) isolated from young, mature, and old animals. Fluid flow produced higher magnitude and more abundant [Ca(2+)](i) oscillations than spontaneous oscillations, suggesting that flow-induced Ca signaling encodes a different cellular message than spontaneous oscillations. ROB from old rats showed less basal [Ca(2+)](i) activity and were less responsive to fluid flow. Cells were more responsive to 0.2 Hz than to 1 or 2 Hz and to 2 Pa than to 1 Pa. These data suggest that the frequency and magnitude of mechanical loading may be encoded by the percentage of cells displaying [Ca(2+)](i) oscillations but that the ability to transduce this information may be altered with age.
authors.affiliation: Department of Biomedical Engineering, Michigan Technological University, Houghton, Michigan 49931-1295, USA. swdonahu@mtu.edu
authors.forename: S W
authors.initials: SW
authors.lastname: Donahue
authors.forename: C R
authors.initials: CR
authors.lastname: Jacobs
authors.forename: H J
authors.initials: HJ
authors.lastname: Donahue
mesh_terms: D000375:Aging / Q000378:metabolism*; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D008297:Male; D010006:Osteoblasts / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344; D013314:Stress, Mechanical
chemical_list: D000469:Alkaline Phosphatase; D002118:Calcium