HUMAN PARATHYROID HORMONE CARBOXYTERMINAL PEPTIDE (53-84) STIMULATES ALKALINE PHOSPHATASE ACTIVITY IN DEXAMETHASONE-TREATED RAT OSTEOSARCOMA CELLS IN VITRO

Previous studies in our laboratory have demonstrated relatively large numbers of cell surface binding sites for the carboxylterminal (53-84) region of PTH on ROS 17/2.8 rat osteosarcoma cells, a clonal osteoblast-like cell line. In order to gain insight into the significance of these carboxylterminal binding sites, we studied the effect of intact bovine PTH (1-84), its aminoterminal fragment bovine PTH (1-34), and the human PTH carboxylterminal fragment (53-84) on alkaline phosphatase activity in dexamethasone-treated rat osteosarcoma (ROS) 17/2.8 cells. While bovine PTH (1-84) and its aminoterminal 1-34 fragment inhibited alkaline phosphatase activity, we saw a dose-related stimulation of activity by human PTH (53-84), with maximal stimulation occurring after 120 hours, at a concentration of 10-8 M. The effect was not seen in dexamethasone-untreated cells. To our knowledge, this is the first published demonstration of biological activity of this carboxylterminal PTH peptide, previously thought to be inac...