Membrane potential changes, cAMP stimulation and contraction in osteoblast-like UMR 106 cells in response to calcitonin and parathyroid hormone.

A multiphasic alteration in membrane potential occurs in response to calcitonin (CT), parathyroid hormone (PTH) and dibutyryl cAMP in the osteoblast-like UMR 106.01 and UMR 106.06 cell lines. This response consists of a small transient hyperpolarization, followed by a transient depolarization, followed by a long-term hyperpolarization. Experiments with channel blockers indicate that the depolarizing phase results from deactivation of K+ channels that are blocked by quinine but not by tetraethylammonium (TEA), and that the long-term hyperpolarization results from activation of K+ channels that are not blocked by quinine or by TEA. Correlating with the stimulation of intracellular cAMP by CT, a small percentage of the UMR 106.06 cells, but not UMR 106.01 cells, contract in response to CT. Both cell lines show a larger percentage of cells contracting in response to PTH than to CT.