Hypotonic swelling of salicylate-treated cochlear outer hair cells

Abstract

The outer hair cell (OHC) is a hydrostat with a low hydraulic conductivity of P-f = 3 x 10(-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 P-f 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 P-f = 3.5 +/- 0.5 x 10(-4) cm/s (mean +/- s.c.m., n = 34) for salicylate-treated OHCs was not significantly different from P-f = 2.4 +/- 0.3 x 10(-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 epsilon(z)/epsilon(c) = -0.76 for salicylate-treated OHCs was significantly smaller (P = .0 143) 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. (c) 2007 Elsevier B.V. All rights reserved.