The effects of prostaglandin E2, parathyroid hormone, 1,25 dihydroxycholecalciferol, and cyclic nucleotide analogs on alkaline phosphatase activity in osteoblastic cells

SummaryClone MC3T3-E1 cells isolated from newborn mouse calvaria had the same type of alkaline phosphatase (ALP) as that found in adult mouse calvaria (the liver-bone-kidney type), as judged by polyacrylamide gel electrophoresis as well as by heat lability and amino acid inactivation. The effects of prostaglandin E2 (PGE2), parathyroid hormone (PTH), 1,25 dihydroxycholecalciferol [1,25(OH)2D3], and adenosine-3′, 5′-cyclic monophosphate (cAMP) analogs on ALP were investigated. PGE2 and 1,25(OH)2D3 increased ALP activity in dose-related manner with a maximal effect at concentrations of 10 ng/ml and 40 pg/ml, respectively. N6,O2-dibutyryl adenosine-3′, 5′-cyclic monophosphate (DBcAMP) also induced an increase in ALP activity in a dose-related fashion with a maximal effect at a concentration of 0.5 mM which was 2.2-fold over that of the controls. Induced ALP was of the “liver-bone-kidney” type. Antinomycin D and cycloheximide inhibited the increase in ALP activity induced by DBcAMP. The level of ALP was elevated by 8-bromo-adenosine-3′,5′-cyclic monophosphate and theophylline, but not by N6,O2-dibutyryl guanosine-3′,5′-cyclic monophosphate and sodium butyrate. Moreover, PGE2 dramatically increased the level of cAMP in the cells with a maximal effect at a concentration of 10 ng/ml, indicating that PGE2 and DBcAMP induce an increase of ALP activity in clone MC3T3-E1 cells by increasing the cAMP level; PTH did not affect enzyme activity and cAMP, level in the cells. These results suggest that PGE2, DBcAMP, and 1,25(OH)2D3 are involved in bone formationin vivo as well.