title: Vitamin D metabolites regulate osteocalcin synthesis and proliferation of human bone cells in vitro.
abstract: The effects of six natural vitamin D metabolites of potential biological and therapeutic interest, 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3), 25-hydroxyvitamin D3 (25-OH-D3), 24R,25-dihydroxyvitamin D3 (24R,25-(OH)2D3), 1,24R,25-trihydroxyvitamin D3 (1,24R,25-(OH)3D3), 25S,26-dihydroxyvitamin D3 (25S,26-(OH)2D3) and 1,25S,26-trihydroxyvitamin D3 (1,25S,26-(OH)3D3) on cell replication and expression of the osteoblastic phenotype in terms of osteocalcin production were examined in cultured human bone cells. At a dose of 5 X 10(-12) mol/1, 1,25-(OH)2D3 stimulated cell proliferation, whereas at higher doses (5 X 10(-9)-5 X 10(-6) mol/1) cell growth was inhibited in a dose-dependent manner. The same pattern of effects was seen for the other metabolites in a rank order of potency: 1,25-(OH)2D3 greater than 1,25S,26-(OH)3D3 = 1,24R,25-(OH)3D3 greater than 25S,26-(OH)2D3 = 24R,25-(OH)2D3 = 25-OH-D3. Synthesis of osteocalcin was induced by 1,25-(OH)2D3 in doses similar to those required to inhibit cell proliferation. Biphasic responses were observed for some of the metabolites in terms of osteocalcin synthesis, inhibitory effects becoming apparent at 5 X 10(-6) mol/1. The cells did not secrete osteocalcin spontaneously. These results indicate that vitamin D metabolites may regulate growth and expression of differentiated functions of normal human osteoblasts.
mesh_terms: D015650:24,25-Dihydroxyvitamin D 3; D002112:Calcifediol / Q000494:pharmacology; D002117:Calcitriol / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000096:biosynthesis*; D002455:Cell Division / Q000187:drug effects; D004100:Dihydroxycholecalciferols / Q000494:pharmacology; D006801:Humans; D006887:Hydroxycholecalciferols / Q000494:pharmacology; D066298:In Vitro Techniques; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D015675:Osteocalcin; D014807:Vitamin D / Q000494:pharmacology*
chemical_list: D002135:Calcium-Binding Proteins; D004100:Dihydroxycholecalciferols; D006887:Hydroxycholecalciferols; D015675:Osteocalcin; D014807:Vitamin D; D015650:24,25-Dihydroxyvitamin D 3; C013721:1,24,25-trihydroxyvitamin D3; C030049:1,25,26-trihydroxyvitamin D3; D002117:Calcitriol; D002112:Calcifediol; C026032:25,26-dihydroxycholecalciferol