The effects of parathyroid hormone (PTH) on cytoplasmic free CA2+ (Cai2+) 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−1μM) induced a rapid transient increase in Cai2+ in 11% of the studied cells. In fura-2 tracings from UMR 106-01 cells in suspension, bPTH 1–34 (0.1 μM) induced a transient increase in Cai2+ in 20% of the experiments. The transient increase in Cai2+ 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 Cai2+ 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 Cai2+.
These data show that PTH causes a release of Ca2+ 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 Cai2+ in osteoblasts.