Figure 1.

Extracellular Ca²⁺ is a principal source of [Ca²⁺]_i in osteocytes under OS. (A) MLO-Y4 cells were pre-loaded with 5 μmol·L⁻¹ Fluo-4 dye and then treated with 0.3 mmol·L⁻¹ H₂O₂ in the presence (control, green line), or absence (low _e[Ca²⁺], purple line) of extracellular Ca²⁺. (B) MLO-Y4 cells were pre-loaded with Fluo-4 dye and then pre-treated with 5 μmol·L⁻¹ U73122 (yellow line), 0.1 μmol·L⁻¹ thapsigargin (TGN, red line) or non-treatment control (purple line) in the absence of extracellular Ca²⁺ prior to the treatment with 0.3 mmol·L⁻¹ H₂O₂. Time laps recording of Ca²⁺ signal took place every 30 s during entire 100 min time period. The black arrow indicates the moment when H₂O₂ was added. The lines correspond to an average of 3 independent experiments where 30 cells were quantified and normalized with non-stimulated rest state. The error bars were omitted in order to clearly show the Ca²⁺ signal pattern.