Calcium Mobilization in Isolated Epithelial Cells of the Endolymphatic Sac

Endolymphatic sac epithelial cells were isolated from the endolymphatic sac of the guinea pig by enzymatic and mechanical dissociation. The intracellular free calcium ion concentrations ([Ca²⁺]i) of the isolated cells were determined using the Ca²⁺-sensitive dye fura-2. The isolated cells were classified into two types, i.e. light and dark cells. In the resting state, [Ca²⁺]i in the cells was variable in both types of cells. In the presence of 200 µ<i>M</i> ATP, there was a rapid rise in [Ca²⁺]i. These findings suggest that endolymphatic sac epithelial cells may have receptor-mediated Ca channels which may play an important role for a nerve-mediated local feedback system of the endolymphatic sac to regulate homeostasis of endolymph volume, pressure and electrolyte balance.