Effect of the phosphodiesterase 4 inhibitor,rolipram, on retinoic acid-increased alkaline phosphatase activity in the mouse fibroblastic C3H10T1/2 cell line

We have evaluated effects of a phosphodiesterase (PDE) 4 inhibitor on retinoic acid-increased alkaline phosphatase activity in the mouse fibroblastic C3H10T1/2 clone 8 (10T1/2) cell line. 10T1/2 cells were cultured in minimum essential medium (MEM) and 10% fetal bovine serum with or without 1 microM retinoic acid and/or the PDE 4 inhibitor, rolipram, and harvested at specific intervals before measurement of alkaline phosphatase activity, cAMP production in response to parathyroid hormone, osteocalcin synthesis and expression, and phosphodiesterase activity. Retinoic acid-increased alkaline phosphatase activity, and slightly enhanced cAMP production in response to parathyroid hormone. However, it did not affect osteocalcin synthesis and expression. In the presence of retinoic acid, PDE 4 activity was not changed. A PDE 4 inhibitor, rolipram, and cAMP analog, 8-bromo-cAMP dramatically increased retinoic acid's ability to induce alkaline phosphatase activity. This is the first report that PDE 4 may be involved in regulation of retinoic acid-increased alkaline phosphatase activity.