WHAT IS THE ROLE OF THE CONVECTIVE CURRENT-DENSITY IN THE REAL-TIME CALCIUM RESPONSE OF CULTURED BONE-CELLS TO FLUID-FLOW

Cultured cells subjected to fluid dow are exposed to mechanical forces and electrokinetic forces. The convective current establishes an elec trokinetic force created by the how-dependent transport of mobile ions in the media over the charged cell surfaces. This current can be expr essed as a current density, the current normalized by the cross-sectio nal area in which it exists. In this study, we hypothesized that the c onvective current density has no role in the bone cell real-time intra cellular calcium response to fluid how. Our hypothesis was tested by i ncorporating electrokinetic measurements and classical electrokinetic double-layer theory to estimate the value of convective current densit y in a parallel-plate how chamber and then to apply an external curren t during the presence of fluid how that would alter convective current density. There was no difference between the mean peak calcium respon se of cells exposed to flow with an altered (canceled or doubled) conv ective current density versus dow with an unmodified convective curren t density, as was measured with fura-2 fluorescence microscopy. These results suggest that mechanical forces, such as fluid-induced shear st ress, rather than concomitant electrokinetic forces are the primary st imuli in eliciting the observed calcium response of bone cells to flui d flow. Copyright (C) 1996 Elsevier Science Ltd.