Effect of furosemide on basal lamina anionic sites in guinea pig labyrinth.

The authors studied the effects of acute furosemide administration on the basal lamina (BL) anionic sites in the stria vascularis, ampullar crista, and endolymphatic sac by using cationic polyethyleneimine (PEI). Furosemide was intravenously administered to albino guinea pigs with normal Preyer's reflexes. After 20 minutes, the bony labyrinth was removed and processed for histologic evaluation. Under a transmission electron microscope, a marked enlargement of the intercellular spaces was observed in the stria vascularis. The PEI distribution decreased significantly on the capillary BL in the stria vascularis and on the subepithelial BL in the sensory, transitional, and dark cell areas. However, no significant change was observed on the capillary BL or the subepithelial BL in the endolymphatic sac. These findings suggest that acute furosemide administration severely alters the distribution of the anionic sites in the strial capillary BL and in the subepithelial BL in the ampullar crista, but not in the capillary BL or the subepithelial BL of the endolymphatic sac.