Outer hair cell length changes in an external electric field. I. The role of intracellular electro-osmotically generated pressure gradients.

Brownell et al. [Science 227, 194-196 (1985)] observed that an isolated, cylindrically shaped cochlear outer hair cell can change its length when an electric field is applied. In their experiments, the cell was fixed at one end, and located between two electrodes which lie on the cell axis but were positioned far from the cell. Kachar et al. [Nature 322, 365-368 (1986)] had suggested that the cell's electrically evoked elongation could be caused by pressure gradients resulting from electro-osmosis of the intracellular fluid. A mathematical model is developed which predicts the length change that would result from electro-osmotically generated pressure gradients inside the cell. Estimated parameter values are included to demonstrate that the pressures generated by electro-osmosis inside the cell would result in elongations that are at least two orders of magnitude below the experimentally measured values.