THE JUNCTIONS OF THE SPINDLE-SHAPED CELLS OF THE STRIA VASCULARIS - ALINK THAT COMPLETES THE BARRIER BETWEEN PERILYMPH AND ENDOLYMPH

It is current opinion that the intercellular spaces of the stria vascu laris represent a closed compartment isolated from the endolymph by th e tight junctions of the marginal cells and from the perilymph by the junctional complexes of the basal cells. However, it has not yet been investigated whether these two barriers meet at the stria margins towa rd Reissner's membrane and the spiral prominence. Possible candidates for this sealing could be junctions between the spindle-shaped cells. In the present study freeze-fracture replicas of guinea pig specimens fixed in the presence of filipin were used in order to investigate the junctions of the spindle-shaped cells and to localize the cholesterol in their plasma membrane. Replicas reveal that, below the belt-like a pical zonula occludens, the basolateral plasma membranes of the spindl e-shaped cells adjacent to each other and to the basal cells are joine d over their entire extension by a large number of junctional strands intermingled with numerous filipin-cholesterol-complexes. Gap junction s are present in the meshes formed by these junctional strands. Thus, the plasma membrane of the spindle-shaped cells shows morphological an d cytochemical characteristics which indicate that they are the anatom ical components completing the barrier isolating the intrastrial compa rtment from the surrounding fluids.