title: Role of increase in intracellular calcium in PTH-induced homologous desensitization in UMR-106 cells.
abstract: Effects of increase in intracellular calcium on PTH-induced homologous desensitization were investigated using calcium ionophores. Pretreatment of UMR-106 cells (rat osteoblast like osteosarcoma cell line) with calcium ionophores (A23187 or ionomycin) for 6h resulted in approximately 50% decrease of PTH-stimulated cAMP production. PTH receptor binding, assessed with 125I-[Nle8,Nle18,Tyr34]PTH-(1-34) as radioligand, was significantly decreased in 10(-6) M calcium ionophore-pretreated (for 6h) cells without affecting the dissociation constant (Kd) for PTH. Minimal effective treatment period was 2h and similar inhibitory effect was observed in 12h-treated cells. These data suggest that increase in intracellular calcium might also act on PTH receptor in the similar manner as protein kinase C activation to induce desensitization.
authors.affiliation: Department of Medicine, Kobe University School of Medicine, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ikeda
authors.forename: T
authors.initials: T
authors.lastname: Sugimoto
authors.forename: M
authors.initials: M
authors.lastname: Fukase
authors.forename: T
authors.initials: T
authors.lastname: Fujita
mesh_terms: D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D015759:Ionomycin / Q000494:pharmacology; D007700:Kinetics; D010006:Osteoblasts / Q000378:metabolism; D012516:Osteosarcoma; D010281:Parathyroid Hormone / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*; D018016:Receptors, Parathyroid Hormone
chemical_list: D010281:Parathyroid Hormone; D011956:Receptors, Cell Surface; D018016:Receptors, Parathyroid Hormone; D000001:Calcimycin; D015759:Ionomycin; D000242:Cyclic AMP; D002118:Calcium