Endolymphatic Sac Obstruction Biochemical Studies

Abstract

Inner ear fluids were studied biochemically in guinea pigs from 1 to 16 weeks after producing endolymphatic hydrops by obstructing the endolymphatic duct. Fluid collected from beneath the footplate showed changes of 50% of the animals indicating distension of the saccule. There was an increase in potassium concentration and decrease in sodium concentration of the collected fluid, indicating a traumatic mixing of endolymph and perilymph produced by rupture of the saccule during collection of the fluid. The smallest changes occurred at one week, and the greatest changes were found four months after endolymphatic sac obstruction. Similar findings were observed in studying inner ear fluids obtained from patients with Ménière's disease. Cochlear endolymph showed biochemical alterations after endolymphatic duct blockage. There was a two- to three-fold increase in sodium concentration and a decrease in potassium concentration with the total ionic concentration remaining approximately the same. Some guinea pigs showed similar changes in vestibular endolymph. This study indicates that in the guinea pig, endolymph obtained in the distended endolymph compartment has a slightly different sodium-potassium ratio as compared to the normal ear. In patients with Ménière's disease there may also be an elevation of endolymph sodium concentration. The significance of this change and hearing loss observed in experimental endolymphatic hydrops and Ménière's disease is open to speculation at the present time.

Regulation of ENaC-mediated sodium transport by glucocorticoids in Reissner's membrane epithelium

“…There are unconfirmed reports of elevated endolymphatic [Na ϩ ] in an animal model of endolymphatic hydrops (36,48), although whether this occurs in cases of Meniere's disease is not known. Nonetheless, in view of the extremely low [Na ϩ ] of endolymph, even a slightly increased leak would lead to sufficient excess Na ϩ in the lumen of the inner ear to draw significant quantities of water in and, thereby, lead to hydrops.…”

Endolymphatic Sodium Homeostasis by Extramacular Epithelium of the Saccule

“…Insight into the relevance of the transepithelial currents reported here can be gained by calculating the corresponding Na ϩ flux and estimating the resulting decrease in saccular Na (Silverstein and Takeda, 1977;Morgenstern et al, 1984) could be reduced to normal (3 mM) (Sellick and Johnstone, 1972) in only 3 h and the volume of saccular endolymph would be reduced at the rate of 4%/h. Quayle et al (1997);5, Stocker (2004);6, Devor et al (1997) and Dutta et al (2009);7, Tanaka et al (2004);8, Duprat et al (19978, Duprat et al ( , 2005, Rajan et al (2000Rajan et al ( , 2005, and Morton et al (2005); 9, Safronov et al (1996), Cai et al (1998), andHadley et al (2000).…”

Glucocorticoid regulation of genes in the amiloride-sensitive sodium transport pathway by semicircular canal duct epithelium of neonatal rat

“…Na ϩ absorption is mediated via amiloride-sensitive epithelial sodium channels (ENaC) in the apical membrane under glucocorticoid control via glucocorticoid receptors (GR) (41). Hypoabsorption of Na ϩ from the vestibular lumen has been suggested to be associated with endolymphatic hydrops, a manifestation of the debilitating condition known as Meniere's disease (33,50).…”