Fig. 4.

Effect of 1α,25(OH)₂D₃ on activation of latent TGF-β1 by MVs. MVs were isolated from confluent cultures of rat costochondral growth zone cartilage cells and assayed for TGF-β1 content by immunoassay (control). MV extracts were then incubated in DMEM containing 10% fetal bovine serum and 10^–8 M 1α,25(OH)₂D₃ without exogenous latent TGF-β1 and basal level of TGF-β1 in the reaction mixture was determined (1,25). MV extracts were then incubated with latent TGF-β1 and active TGF-β1 was measured (MV). MVs were treated with 1α,25(OH)₂D₃ and extracts of these MVs were incubated with latent TGF-β1 (MV+1,25). Finally, extracts from MVs treated with 10^–8 M 1α,25(OH)₂D₃ were incubated with latent TGF-β1 in the presence of the MMP inhibitor 1,10 phenanthroline (MV+1,25+PHE). Data are means ± SEM for 6 separate MV preparations. ∗ p < 0.05, MV versus control; ⁺ p < 0.05, MV+1,25 versus MV; ° p < 0.05, MV+1,25 versus MV+1,25+PHE.