Electron microscopical investigations showed tight junctions in marginal and dark cells, which form the secretory epithelia of the cochlea and of the vestibular organ, respectively [11]. Morphologically, the tight junctions of sensory and stria vascularis epithelia are described as very tight with respect to the number of strands visible in freeze fracture images. These epithelia contain more strands than others lining the endolymphatic space [12]. At the apical side of the marginal cells and in basal cells, the intracellular, tight junction-associated protein ZO-1 was found [13]. The integral tight junction-protein claudin-14 was not found in the stria vascularis [12]. Little else is known, however, about the tight junctions of marginal cells.
In the present study, we investigated the expression of integral tight junction-proteins, claudin-1 to -4 and occludin, in the stria vascularis of guinea pig cochlea and visualized them in the tight junctions of the marginal cells.