Observations on the stria vascularis of the guinea pig cochlea and the changes resulting from the administration of the diuretic furosemide.

An electron microscope examination of the stria vascularis of guinea pigs and the structural changes occurring after administration of furosemide has been made. The use of ruthenium-red, which stains cell coats, has shown that the atria is impermeable to the passive diffusion of material from both the endolymph and the spiral ligament. The first changes after administration of furosemide are observed 4 hours after injection; small spaces develop between the cells. After 5--6 hours the spaces have enlarged but the tight junctions between marginal cells remain intact. The intermediate cells show signs of atrophy. In severely affected animals the intermediate cells have so shrunk that the spaces are very large and the marginal cells clearly resolved. These latter cells show no structural damage. In this severely affected tissue it is seen that the blood vessels are entirely surrounded by marginal cell extensions. It is suggested that the intermediate cells may have a regulatory function. The damage appears to be recoverable, since 6 hours after injection the spaces have decreased in size although some signs of intermediate cell atrophy are still apparent.