Stimulatory effects of parathyroid hormone and 1,25-dihydroxyvitamin D 3 on insulin-like growth factor-binding protein-5 mRNA expression in osteoblastic UMR-106 cells: the difference between transient and continuous treatments

Abstract

The transient treatment with parathyroid hormone (PTH) for 12 h, followed by its removal for 36 h, stimulated insulin-like growth factor-binding protein (IGFBP)-5 mRNA expression more strongly than the continuous treatment for 48 h in osteoblastic UMR-106 cells. The transient but not continuous treatment with A23187 also stimulated it. In contrast, 1,25-dihydroxyvitamin D 3 stimulated it, irrespective of the treatment design. IGFBP-5 stimulated type-1 procollagen mRNA expression. The present study first indicated that the transient treatment with PTH more effectively stimulated IGFBP-5 mRNA expression than its continuous treatment partly via an increase in intracellular calcium and suggested that IGFBP-5 might be involved in the anabolic action of PTH in bone.