STIMULATORY EFFECTS OF PARATHYROID-HORMONE AND 1,25-DIHYDROXYVITAMIN D-3 ON INSULIN-LIKE GROWTH FACTOR-BINDING PROTEIN-5 MESSENGER-RNA EXPRESSION IN OSTEOBLASTIC UMR-106 CELLS - THE DIFFERENCE BETWEEN TRANSIENT AND CONTINUOUS TREATMENTS

The transient treatment with parathyroid hormone (PTH) for 12 h, follo wed by its removal for 36 h, stimulated insulin-like growth factor-bin ding protein (IGFBP)-5 mRNA expression more strongly than the continuo us 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 treatmen t design, IGFBP-5 stimulated type-1 procollagen mRNA expression, The p resent study first indicated that the transient treatment with PTH mor e effectively stimulated IGFBP-5 mRNA expression than its continuous t reatment partly via an increase in intracellular calcium and suggested that IGFBP-5 might be involved in the anabolic action of PTH in bone. (C) 1997 Federation of European Biochemical Societies.