Figure 5. Calcitonin inhibits osteoclast apoptosis through Bcl-2 and Erk signaling.

(A) Western blot analysis of expression of caspase 3 and 9. Osteoclasts were first treated with HA14-1 (50 µM) for 2 h and then CT (10 nM), SDCP (10 µM), or both were added to the culture medium. (B) Examination of apoptotic signaling regulated by calcitonin and SDCP in the presence of an Erk inhibitor. Osteoclasts were first treated with PD98059 (5 µM) for 2 h and then CT (10 nM), SDCP (10 µM), or both were added to the culture medium. Protein levels were quantified by densitometry, corrected for the sample load based on actin expression, and expressed as fold-increase or decrease relative to the control lane. Each blot is representative of at least three replicate experiments.