Much controversy surrounds observed in vitro and in vivo effects from exposure to specific combinations of weak static and time-varying magnetic fields called ion resonance magnetic fields (<1.0 mT and 3100 Hz). The controversy is that no adequate mechanism has been formulated and that many of the published effects have not been reproduced. Cytosolic Ca²⁺ has been implicated in the response but has not been unequivocally shown to increase in vitro in cells during field exposure. This was the objective of this study.

The model used in this study was the primary culture calvarial bone cell which is known to alter proliferation in response to weak electric fields. Magnetic field amplitude, frequency and orientation were taken from the literature where exposure to similar fields has brought about significant effects in vitro. Other variables included culture age and serum concentration during field exposure. Cytosolic Ca²⁺ concentration was measured in single cells via fura-2 fluorescence microscopy. The effect of applied electric fields (0.1-0.15 V/m at 6 kHz-1.5 MHz) on Ca²⁺ was also examined, but only as a preliminary study.

Several magnetic field combinations illicited significant effects seen as Ca²⁺ spikes in single cells, but only when serum was present in the bathing medium. In addition, applied electric fields in a frequency window of 20 kHz-300 kHz induced spikes, however, with no serum being present during these experiments.

It can be concluded that there is some mechanism whereby these weak magnetic and electric fields are sensed by these cells. This mechanism seems to be linked to serum only for the case of the applied magnetic fields suggesting a different mechanism than that occurring for the applied electric fields. The findings presented here may be considered as being independent confirmation for the literature from which the field parameters were obtained. Field amplitude and serum dose-responses studies, and serum constituent studies are suggested for future investigations.