Effects of parathyroid hormone on cAMP production and alkaline phosphatase activity in osteoblastic clone MC3T3-E1 cells.

The effect of parathyroid hormone (PTH) was tested on osteoblastic cells (clone MC3T3-E1) cultured in serum-free medium containing 0.3% bovine serum albumin. PTH stimulated an increase in cAMP production in a dose-related fashion up to a concentration of 0.5 unit/ml, the maximum increase being 23-fold above that of controls. Although PTH did not affect DNA content, this peptide also increased dose-dependently alkaline phosphatase activity up to a concentration of 0.5 unit/ml. PTH plus isobutylmethyl xanthine elevated enzyme activity 1.5-fold over that in PTH-treated cells. These results strongly indicate that PTH has a direct stimulatory effect on the differentiation of osteoblasts via intracellular cAMP production in vitro.