Hypotonic swelling of salicylate-treated cochlear outer hair cells

Abstract

The outer hair cell (OHC) is a hydrostat with a low hydraulic conductivity of Pf=3x10(-4) cm/s across the plasma membrane (PM) and subsurface cisterna that make up the OHC's lateral wall. The SSC is structurally and functionally a transport barrier in normal cells that is known to be disrupted by salicylate. The effect of sodium salicylate on Pf is determined from osmotic experiments in which isolated, control and salicylate-treated OHCs were exposed to hypotonic solutions in a constant flow chamber. The value of Pf=3.5+/-0.5x10(-4) cm/s (mean+/-s.e.m., n=34) for salicylate-treated OHCs was not significantly different from Pf=2.4+/-0.3x10(-4) cm/s (mean+/-s.e.m., n=31) for untreated OHCs (p=.3302). Thus Pf is determined by the PM and is unaffected by salicylate treatment. The ratio of longitudinal strain to radial strain epsilonz/epsilonc=-0.76 for salicylate-treated OHCs was significantly smaller (p=.0143) from -0.72 for untreated OHCs, and is also independent of the magnitude of the applied osmotic challenge. Salicylate-treated OHCs took longer to attain a steady-state volume which is larger than that for untreated OHCs and increased in volume by 8-15% prior to hypotonic perfusion unlike sodium alpha-ketoglutarate-treated OHCs. It is suggested that depolymerization of cytoskeletal proteins and/or glycogen may be responsible for the large volume increase in salicylate-treated OHCs as well as the different responses to different modes of application of the hypotonic solution.

A Stokesian analysis of a submerged viscous jet impinging on a planar wall

“…This concept of mechanoporation and its application in the wider area of cellular physiology needs to be explored more fully. Finally, it will be interesting to see how the wall stress and wall pressure are affected by mass transfer (Nakagawa et al 1990;Housley et al 1992;Lin et al 1993;Santos-Sacchi et al 2006), permeable plane wall (Ratnanather et al 1996;Morimoto et al 2002;Zhi et al 2007), slip on the plane wall (Lauga, Brenner & Stone 2007) and oscillating inflow (Brundin & Russell 1994).…”

“…Thirdly, increased hydraulic conductivity, or equivalently rate of volume change due to water intake accompanied by a reduction in the ratio of the principal values of the anisotropic i.e. orthotropic strains of the cell wall, was observed when hypoosmotic extracellular solution was applied close to the cell (Morimoto et al 2002;Zhi et al 2007;Farahbakhsh, Zelaya & Narins 2010). Reviews (Brownell 2006;Spector et al 2006) hypothesize that the increase in the magnitude of the wall pressure and wall shear stress along the lateral wall of the cell due to the reduced distance of the wall from the orifice alters the biophysical properties of the wall, resulting in the increase in cellular response to the perfusate.…”

Biophysical Mechanisms Underlying Outer Hair Cell Loss Associated with a Shortened Tectorial Membrane

“…OHCs are known to be vulnerable to excess electromotility (Brownell 1986;Evans 1990), and the OHC plasma membrane has been identified as a target that is particularly sensitive to mechanical alteration (Chertoff and Brownell 1994;Morimoto et al 2002;Zhi et al 2007). We used an alternating current stimulus at acoustic frequencies to emulate the stimuli experienced by OHCs in vivo, and our findings support this concept.…”

“…In particular, the OHC plasma membrane has been identified as a structure that is particularly sensitive to mechanical alteration (Chertoff and Brownell 1994;Morimoto et al 2002;Oghalai et al 1998Oghalai et al , 1999Oghalai et al , 2000Zhi et al 2007). Therefore, we hypothesized that one potential factor underlying the differential susceptibility of OHCs to noise between the genotypes is that Tecta C1509G/+ and Tecta…”

Closure of supporting cell scar formations requires dynamic actin mechanisms

“…Intracellular pressure may contribute to hair cell extrusion, for example, depolymerization of F-actin, the cortical cytoskeleton and/or glycogenic stores may lead to an increase in osmolytes within the cell, drawing water into the cell and hence swelling (Jiang et al, 2006a;Zhi et al, 2007). In contrast, mammalian inner hair cell blebbing occurred in hyper-osmotic conditions in vitro, suggesting that intracellular pressure is not required (Shi et al, 2005).…”