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© The Rockefeller University Press, 0022-1295/1998//447/ $5.00
Journal of General Physiology, Volume 112, Number 4, 1998

Article

Effect of Membrane Tension on Gap Junctional Conductance of Supporting Cells in Corti's Organ

Hong-Bo Zhao and J. Santos-Sacchi

From the Sections of Otolaryngology and Neurobiology, Yale University School of Medicine, New Haven, Connecticut 06510

The effects of turgor pressure-induced membrane tension on junctional coupling of Hensen cell isolates from the inner ear were evaluated by input capacitance or transjunctional conductance measurement techniques. Turgor pressure was altered by changing either pipette pressure or the osmolarities of extracellular solutions. Both positive pipette pressure and extracellular applications of hypotonic solutions, which caused cell size to concomitantly increase, uncoupled the cells as indicated by reduced input capacitance and transjunctional conductance. These changes were, in many cases, reversible and repeatable. Intracellular application of 50 µM H-7, a broad-based protein kinase inhibitor, and 10 mM BAPTA did not block the uncoupling effect of positive turgor pressure on inner ear gap junctions. The transjunctional conductance at a holding potential of –80 mV was 53.6 ± 5.8 nS (mean ± SEM, n = 9) and decreased ~40% at a turgor pressure of 1.41 ± 0.05 kPa. Considering the coincident kinetics of cell deformation and uncoupling, we speculate that mechanical forces work directly on gap junctions of the inner ear. These results suggest that pathologies that induce imbalances in cochlear osmotic pressure regulation may compromise normal cochlear homeostasis.

Key Words: cochlea • membrane tension • turgor pressure • gap junctions • Hensen cells

Address correspondence to Joseph Santos-Sacchi, Ph.D., Professor, Surgery (Otolaryngology), BML 244, Yale University School of Medicine, 333 Cedar St., New Haven, CT 06510. Fax: 203-737-2245; E-mail: joseph.santos-sacchi{at}yale.edu

Abbreviations: in, input capacitance; Gj, transjunctional conductance; OHC, outer hair cell; Rin, input resistance; Rs, series resistance


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