EFFECTS OF PARATHYROID-HORMONE ON CYCLIC AMP-FORMATION AND CYTOPLASMIC FREE CA-2+ IN THE OSTEOSARCOMA CELL-LINE UMR-106-01

The effects of parathyroid hormone (PTH) on cytoplasmic free Ca2+ (Ca(i)2+) and cAMP-formation were investigated in the rat osteosarcoma cell line UMR 106-01. In fura-2 loaded adherent single cells bPTH 1-34 (10 nM - 1-mu-M) induced a rapid transient increase in Ca(i)2+ in 11% of the studied cells. In fura-2 tracings from UMR 106-01 cells in suspension, bPTH 1-34 (0.1-mu-M) induced a transient increase in Ca(i)2+ in 20% of the experiments. The transient increase in Ca(i)2+ seen in suspensions of cells was not abolished by addition of EGTA (2.5 mM) prior to challenge with PTH, suggesting that the increase in Ca(i)2+ was derived from intracellular stores. A marked rapid increase in cAMP-formation was observed in all experiments with cells in suspension, also in the experiments where PTH did not affect Ca(i)2+. These data show that PTH causes a release of Ca(i)2+ from intracellular stores in a small percentage of osteosarcoma UMR 106-01 cells, and that PTH is capable of inducing an increase in cAMP-formation without affecting Ca(i)2+ in osteoblasts.