ESTROGEN AND PARATHYROID-HORMONE REGULATE INSULIN-LIKE-GROWTH-FACTOR BINDING PROTEIN-4 IN SAOS-2 CELLS

The effect of 17 beta-estradiol and parathyroid hormone (PTH) on the e xpression of insulin-like growth factor-binding protein-4 (IGFBP-4) me ssenger:RNA (mRNA) was studied in the cultured human osteoblast-like S aOS-2 cells. Treatment of SaOS-2 cells with PTH for 3 h caused 3.3-fol d increase in IGFBP-4 mRNA levels which was determined by reverse tran scription-polymerase chain reaction. 17 beta-Estradiol had no effect o n either the stimulation of mRNA level by PTH or the basal level. Toge ther with our previous report that 17 beta-estradiol inhibits the PTH- induced reduction of IGFBP-4 proteolysis in these cells, the results o btained may help to explain the mechanisms of determining IGFBP-4 avai lability by systemic hormones in osteoblast cells.