Hypotonic swelling of salicylate-treated cochlear outer hair cells

The outer hair cell (OHC) is a hydrostat with a low hydraulic conductivity of Pf = 3 × 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 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 ± 0.5 × 10−4 cm/s (mean ± s.e.m., n = 34) for salicylate-treated OHCs was not significantly different from Pf = 2.4 ± 0.3 × 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 εz/εc = −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 α-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.