title: Alkaline phosphatase inhibition by parathyroid hormone and isoproterenol in a clonal rat osteosarcoma cell line. Possible mediation by cyclic AMP.
abstract: The effect of parathyroid hormone (PTH 1-34 bovine) on alkaline phosphatase activity was investigated in an osteoblast-like clonal cell line derived from rat osteosarcoma (ROS 17/2). ROS 17/2 alkaline phosphatase resembled the bone enzyme in levamisole sensitivity and electrophoretic mobility but differed in heat stability. The specific activity of ROS 17/2 alkaline phosphatase increased with time in culture. This increase was inhibited by PTH (1-34) and (-)-isoproterenol in a dose-dependent manner starting at near-physiological hormone concentrations. The ID50 values were 0.02 nM for PTH (1-34) and 1.7 nM for isoproterenol. The two hormones stimulated ROS 17/2 adenylate cyclase, albeit at higher concentrations: Km values were 13 nM for PTH (1-34) and 16 nM for isoproterenol. The rise in alkaline phosphatase was also inhibited by dibutyryl cyclic AMP and 8-bromocyclic AMP (0.1 mM). These findings further document the osteoblastic properties of the ROS 17/2 osteosarcoma cell line, suggest that PTH inhibition of alkaline phosphatase represents a physiological response to the hormone in these cells, and implicate cyclic AMP as a mediator of this PTH effect.
mesh_terms: D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors*; D000818:Animals; D001859:Bone Neoplasms / Q000201:enzymology*; D003994:Bucladesine / Q000494:pharmacology; D002460:Cell Line; D000242:Cyclic AMP / Q000502:physiology*; D004591:Electrophoresis, Polyacrylamide Gel; D004790:Enzyme Induction / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology; D012516:Osteosarcoma / Q000201:enzymology*; D010281:Parathyroid Hormone / Q000502:physiology*; D051381:Rats
chemical_list: D010281:Parathyroid Hormone; D003994:Bucladesine; D000242:Cyclic AMP; D000469:Alkaline Phosphatase; D007545:Isoproterenol