Specific down-regulation of parathyroid hormone (PTH) receptors and responses to PTH by tumour necrosis factor α and retinoic acid in UMR 106-06 osteoblast-like osteosarcoma cells

Abstract

Parathyroid hormone (PTH) and PTH-related protein (PTHrP) act via PTH receptors in bone to stimulate bone resorption. Bone resorption is also stimulated by certain cytokines, which are produced in bone and bond marrow. The effects of such cytokines on the PTH-receptor system were studied in the osteoblast-like osteosarcoma cell line UMR 106-06. 125I-labelled PTHrP-(1-84)-peptide bound specifically to the cells, and PTHrP (1-34) and (1-84) competed with equimolar affinity for binding to UMR 106-06 cells. The specific binding of 125I-PTHrP-(1-84) could be completely blocked by PTH. Therefore 125I-PTHrP-(1-84) bound to a classical PTH receptor in UMR 106-06 cells. Preincubation for 3 days with ..