Phosphate stimulates differentiation and mineralization of the chondroprogenitor clone ATDC5

ATDC5 cells were employed to examine how inorganic phosphate (Pi) influence s chondrocytic bone formation. 1) Pi (3 - 30 mM) plus ascorbic acid (50 mug /ml) dose-dependently accelerated proliferative differentiation and mineral ization of ATDC5. 2) Northern blot analysis revealed that 10 mM Pi suppress ed expression of type II collagen and PTH (parathyroid hormone) / PTH-relat ed peptide (PTHrP) receptor, while it accelerated type X collagen expressio n. 3) Pi (3 - 30 mM) dose-dependently increased luciferase activity in the cells transfected with 3000 bp type X collagen promoter fused to the lucife rase gene. The results suggest a regulatory role of Pi in endochondral oste ogenesis.