Influence of changed blood pH on anionic sites in the labyrinth

Using polyethyleneimine as a cationic probe, changes in the anionic sites of the labyrinthine basal laminae occurred during acidosis and alkalosis. Hartley-strain guinea pigs (200-300 g) with normal Preyer's reflex were injected i.v. with 0.5% polyethyleneimine (PEI, mol. wt 1800) solution adjusted to pH 7.3 with HCI via an axillary vein. The animals were divided into three groups: control, acidosis, and alkalosis. Acidosis was produced by inducing hypoxia, and alkalosis by injecting 7% NaHCO3. In controls, anionic sites were demonstrated on the basal laminae in the labyrinth. During both acidosis and alkalosis, a decreased number of anionic sites were observed on the basal laminae of the capillary walls in both stria vascularis and subepithelial layer of the vestibular sensory epithelium. However, an increase in anionic sites was observed on the basal lamina in Reissner's membrane during both acidosis and alkalosis.