Transepithelial voltage and resistance of vestibular dark cell epithelium from the gerbil ampulla

Transepithelial voltage (Vt) and resistance (Rt) were measured across the dark cell epithelium of the gerbil ampulla using a micro Ussing chamber of improved design in order to test the view that the histologically similar epithelia in the utricle and in the ampullae exhibit similar electrophysiologic functions. Vt was found to be 8.0 +/- 0.3 mV and Rt was 11.6 +/- 0.4 ohm-cm2 (N = 179) when both sides of the tissue were perfused with symmetric perilymph-like solution. The equivalent short circuit current (Isc = Vt/Rt) was 712 +/- 18 microA/cm2 (N = 179). Isc was reduced from 638 +/- 60 to 48 +/- 16 microA/cm2 (N = 14) by basolateral perfusion of 10(-3) M ouabain and from 538 +/- 27 to 27 +/- 4 microA/cm2 (N = 15) by basolateral perfusion of 5 x 10(-5) M bumetanide. Basolateral K+ steps (Na+ substitution) from 3.6 to 25 mM increased Vt from 6.5 +/- 0.5 to 12.2 +/- 0.6 mV and reduced Rt from 9.7 +/- 0.7 to 7.4 +/- 0.5 ohm-cm2 (N = 43). Apical K+ steps from 3.6 to 25, to 100 mM or to 145 mM led to a decrease in both Vt and Rt. The steady state Vt during apical perfusion of 145 mM K+ was near zero. Upon return to 3.6 mM K+, Vt transiently overshot its original level. Apical Cl- steps from 150 to 50 mM (gluconate substitution) monophasically decreased Vt from 5.9 +/- 0.7 to 4.1 +/- 0.8 mV (N = 15) and increased Rt from 9.6 +/- 1.3 to 12.0 +/- 1.5 ohm-cm2 (N = 14).(ABSTRACT TRUNCATED AT 250 WORDS)