Effects of ascorbic acid, calcitriol, and retinoic acid on the differentiation of preosteoblasts

Abstract

The responses of the immortalized rat preosteoblast UMR‐201‐10B to ascorbic acid (AA), 1,25(OH)2D3 (calcitriol), and retinoic acid (RA) were examined. UMR‐201‐10B cells have an undetectable basal alkaline phosphatase (ALP) activity that is induced after 24 h of treatment with 10−6 M RA (4.64 ± 0.06 μmol/h/mg of protein). The addition of 10−8 M calcitriol resulted in a slight induction of ALP activity after 72 h (0.43 ± 0.07 μmol/h/mg of protein). When calcitriol was added to RA, however, over the same period ALP activity was enhanced significantly compared with treatment with RA alone (RA and calcitriol, 12.29 ± 0.86 μmol/h/mg of protein). Treatment with AA (50 μg/ml) alone had no effect on ..