Homeostasis of the Endolymph and Endolymphatic Sac

• Published in: Equilibrium Research Vol. 50; no. 2; pp. 145 - 148
• Main Authors: Hirakawa, Katsuhiro, Takumida, Masaya, Oda, Kazunari, Date, Tomohito, Harada, Yasuo
• Format: Journal Article
• Language: English; Japanese
• Published: Japan Society for Equilibrium Research 1991
• Subjects: endolymph; endolymphatic sac; guinea pig; regulatory function glycerol
• ISSN: 0385-5716; 1882-577X
• DOI: 10.3757/jser.50.145

The endolymphatic sac has been considered to absorb endolymph. Recent studies have revealed that the endolymphatic sac also has a secretory capacity and is closely involved in the regulation of inner ear fluid volume and pressure. This study was designed to investigate this regulatory function of the andolymphatic sac in an animal model in which the andolymphatic sac and duct had been obliterated unilaterally. Fifteen guinea pigs were used in this study. Twenty four hours after obliteration of the right endolymphatic sac and duct, glycerol was injected intraperitoneally. The animals were sacrificed under general anesthesia, 15, 30 minutes, 1, 2, 4 and 24 hours after the injection of glycerol. The temporal bones were dissected out and fixed with 10% formalin and decalcified with 0.1 M buffered Na-EDTA for 1 month. The specimens were embedded in Agar 100 resin. The sections were stained with toluidine blue and examined with a light microscope. One to 2 hours after injection, collapse or folding of Reissner's membrane was observed in the operated cochlea with obliterated endolymphatic sac and duct. No remarkable change of Reissner's membrane was found in the non-operated ear with normal endolymphatic sac and duct. In the lumen of the endolymphatic sac of the non-operated ears, material stained with toluidine blue appeared 15 minutes after the injection of glycerol. The volume of this material increased with time and could still be seen 4 hours after the glycerol injection. Twenty four hours after the glycerol injection, no toluidine blue stained material could be seen. These findings suggested that the endolymphatic sac has a secretory capacity and plays an important role in the regulation of inner ear fluid volume and pressure.