Cellular localization of adenylate cyclase in the developing and mature inner ear of the mouse

The localization of adenylate cyclase in the developing and mature inner ear of the CBA/CBA mouse' in in Shaker-1 and Shaker-2 mutants and in organ culture was determined by a histochemical procedure with adenylyl imidodiphosphate as substrate and Sr2+ as capture ion. Enzymatic activity was associated with cell membranes in stria vascularis and Reissner's membrane but could not be demonstrated in other cochlear structures. In stria vascularis, adenylate cyclase was found on the contraluminal infoldings of marginal cells but not on their luminal surface, while Reissner's membrane showed activity on its endolymphatic surface. Activity was also associated with utricular dark cells. Essentially the same localization but differing in quantitative aspects was observed during development, in organ culture and in the mutant strains. The speculative role of adenylate cyclase in cochlear ion and fluid balance is discussed.