An anionic charge barrier in the guinea pig cochlea.

A charge barrier has been found in the glomerular basement membrane of the kidney and plays an important role in the filtration of solutes. In the present study, we used electron microscopy to localize anionic sites of a similar charge barrier in the guinea pig cochlea. Polyethyleneimine (PEI) was used as a cationic marker to detect anionic sites. Our results showed a localization of PEI with regular interspaces, indicating the anionic sites to the charge in the capillary basement membrane of the stria vascularis and the spiral ligament, and in the basal lamina of Reissner's membrane and the spiral prominence. This charge barrier, as well as structural size barrier, may play an important role in the maintenance of normal inner ear functions.