Abstract
Basal lamina (BL) anionic sites are considered to act as negative charge barriers that contribute to the selective permeability of electrically charged macromolecules and ions in the labyrinth. Transmission electron microscopy was used to study the effects of acute furosemide administration on the basal lamina (BL) anionic sites in the stria vascularis, dark cell area, and the endolymphatic sac using cationic polyethyleneimine (PEI, M.W. 1800). Albino guinea pigs with normal Preyer's reflex were used in this study. Furosemide (80 mg/kg. B.W.) and physiological saline was administered intravenously via the axillary vein to each animal in the experimental and control groups, respectively. After 20 min, auditory bullae were removed and processed for histological evaluation. A marked enlargement of the intercellular space was observed in the stria vascularis. No marked edematous change was observed in the epithelium in the dark cell area. PEI distribution was significantly decreased on the capillary BL in the stria vascularis and on the subepithelial BL in the dark cell area. These findings suggest that the water and ionic transport system in the stria vascularis may be different from that in the dark cell area. No significant difference of the PEI distribution was observed on the subepithelial BL in the endolymphatic sac. These findings suggest that furosemide severely alters the distribution of the anionic sites in the strial capillary BL and in the subepithelial BL in the dark cell area but not in the subepithelial BL of the endolymphatic sac. Hence, we propose that the charge barrier may not be injured in the endolymphatic sac following the administration of furosemide.
