Structural features of the basal lamina in Reissner's membrane of the guinea pig.

The structural features of the basal lamina in Reissner's membrane were examined electron microscopically using tannic acid fixation, poly-cationic staining (ruthenium red), and mono-cationic staining (safranin O). Tannic acid fixation revealed 5-10-nm filaments which ran perpendicularly between the lamina densa and the cytoplasmic surface of squamous epithelial cells. Ruthenium red staining showed a lattice-like arrangement of anionic sites on both sides of the lamina densa. Safranin O staining revealed filamentous networks at the same sites. These structural features of the basal lamina in the Reissner's membrane were very similar to those of the glomerular and the alveolar basement membrane. Therefore, the possibility that anionic sites of Reissner's membrane may play the role of a size and charge-selective barrier between the scala media and the scala vestibuli, in much the same way that the glomerular basement membrane plays the same role of barrier, must be taken into account.