The ratio of elastic moduli of cochlear outer hair cells derived from osmotic experiments

Outer hair cells (OHCs) were subjected to three different hypo-osmotic challenges which induced shape changes in OHCs. The longitudinal and circumferential strains, epsilon z and epsilon c, respectively, were extracted from a morphometric analysis of video images of the cells. A value of epsilon z/epsilon c = -0.72 was obtained and was found to be independent of the applied osmotic gradient. Using an elastic isotropic membrane model for the OHC lateral wall, the ratio of the elastic shear modulus mu to the elastic area expansion modulus K was calculated yielding a value of 0.054. The contribution of this ratio to OHC mechanics is discussed.