[The localization and the function of carbonic anhydrase in the inner ear]

Carbonic anhydrase (CA) is distributed in a wide variety of animal cells and tissues, especially in cells and tissues involved in rapid exchange or transport of protons, bicarbonate, or other ions. Although localization of this enzyme and its physiological roles in the inner ear have been investigated extensively, full clarification has yet to be achieved. We have conducted a histochemical investigation of CA localization in the inner ear of the guinea pig by Hansson's method, with emphasis on improved fixation. The histochemical reaction for CA activity is localized in the outer and inner hair cells of the organ of Corti, Deiters' cells or nerve endings, inner pillar cells, Boettcher's cells, stria vascularis, spiral ligament, vasculo-epithelial zone and spiral ganglion cells. The physiological roles of CA in the inner ear, particularly in relation to the production or absorption of endolymph, are discussed in this report.