On the relationship between streaming potential and strain in an in vivo bone preparation

Transcortical streaming potentials were measured at each of two cortical-surface sites with respect to a reference electrode in the medullary canal, in the left ulnae of six live, adult (2 yr-old), male 18.2 +/- 1.4 kg domestic turkeys, under general anesthesia, for each of two loading conditions. We observed that the relationship among streaming potential magnitude, surface strain, and strain gradient is not as simple as anticipated. Under predominantly axial and bending load conditions, significantly different strain and strain gradients were generated at the two recording sites. However, no significant differences were detectable in transcortical streaming potentials for one of the loading conditions, and only a slight difference was detected in the other. Conversely, correlations of streaming potential magnitude to strain at both sites show robust relationships (r2 = 0.45, P - 0.02), albeit with different slopes for the two sites. These findings may have implications for the contribution of streaming potentials, or at least, fluid flow to the stimulation of bone cells.