Ionic Currents at the Growth Plate of Intact Bone: Occurrence and Ionic Dependence

Electric phenomena are well known to be related to growth, healing, and regeneration of tissues. Several lines of evidence suggest that electric currents are closely related to growth plate activity. This study characterizes the ionic current naturally occurring at the growth plate and determines its ionic dependence. Our experimental model was the intact metatarsal bone of weanling mice; ionic exchanges at the medium-growth plate interface were studied on bones immersed in physiological media, and the associated currents were measured by means of a two-dimensional vibrating probe system. The results showed that growth plate of weanling mice drives electric ionic currents with a typical distribution pattern. The maximum current vector emerges from the equatorial plane of the growth plate and reverses as soon as bicarbonate ion is added. In adult mouse metatarsal bone, where the typical growth plate morphology is not recognizable any more, the current was no longer detectable. The bicarbonate dependent effect on the current is modulated by acetazolamide. In conclusion, growth plate of intact bone ex vivo drives steady electric currents, with a highly reproducible pattern. The ionic dependence of the current suggests the presence of an ionic exchange system between the growth plate interstitial fluid and the systemic