1995 Volume 61 Issue 6 Pages 1026-1030
Translocation of blood calcium to otoliths across the saccular epithelium was examined pharmacologically using an isolated preparation of the otolith-containing sacculus from rainbow trout. Mannitol added to the incubation medium virtually did not permeate into endolymph, indicating that intercellular junctions are tight for calcium to diffuse through a paracellular pathway. The addition of lanthanum or gadolinium to the incubation medium led to a marked decrease in the rate of calcium deposition on otoliths. Verapamil and diltiazem had no effect on the deposition, while Reactive blue reduced the rate to 60% of the control. Although the replacement of sodium with choline in the incubation medium did not change the rate of calcium deposition on otoliths, ouabain reduced the rate in a concentrationdependent way. Chlorpromazine was also effective for the reduction. These results suggest that receptor-operated calcium channels facilitate calcium influx into saccular cellsacross the basolateral membrane and that cytosolic calcium is extruded to the otolith across the distalmembrane by the Na+- Ca2+ exchanger and ATP-dependent calcium pump.
