Measurements and a model of outer hair cell hydraulic conductivity
Ratnanather, J.T., Zhi, M., Brownell, W.E. and Popel, A.S.
Hearing Research, Vol 96, 33-40. July 1996.
The hydraulic conductivity of the cochlear outer hair cell (OHC) is central to the maintenance of the positive intracellular pressure necessary for its function as the cochlear amplifier. A mathematical model of osmotic water transport across the OHC membrane is formulated. The model relates the OHC hydraulic conductivity, L_p, to the rate of volume change in response to osmotic stimuli. L_p is evaluated from osmotic experiments in which isolated OHCs are exposed to an hypotonic solution. The rate of volume increase in response to the hypotonic challenge was determined by a morphometric analysis of video images of cells. L_p was found to be about 10^-14 m/s/Pa or equivalently, P_f about 10^-4 cm/s. This is on the low side of values reported for different lipid bilayers, and is two orders of magnitude lower than the hydraulic conductivity of red blood cells. The relation of the low OHC hydraulic conductivity to the composition and morphology of its membranes is discussed.
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