Response of cultured bone cells to a capacitively coupled electric field: inhibition of cAMP response to parathyroid hormone.

Fetal rat calvarial bone cells grown in monolayers were exposed to a capacitively coupled electrical field of 2.62 mV/cm for 2.5-30 min. There was a 59% increase in cAMP concentration after electrical stimulation, compared with a 3615% increase after parathyroid hormone (PTH) administration. PTH administration after electrical stimulation resulted in less cAMP synthesis than following either electrical stimulation alone or PTH administration alone. When PTH administration was delayed for 30 min following cessation of the electrical stimulation, there was an inhibition in the cAMP response. This suggests that one possible mechanism of electrically induced osteogenesis is the desensitization of the bone cell to PTH. Since the effect of PTH is to increase bone resorption, desensitizing or blocking the effects of PTH at the bone cell level would result in a net increase in bone formation.