Distribution of (Na+, K+) ATPase, α-subunit in the rat stria vascularis was studied using immunoelectron microscopy. Many enzymes localize on the basolateral membrane of the marginal cell and of the cell membrane of the intermediate cell facing to the marginal cell. The density of (Na+, K+) ATPase on the both cells is almost equal to that on that on the basolateral membrane of the renal tubule cell. This finding suggests that marginal cell plays an important role to produce the endocochlrar potential and to maintein the endocochlear ionic composition. Intermediate cell also may participate in the ion transport of the stria vascularis.
