Morphology of the endolymphatic sac in the guinea pig after an acute endolymphatic hydrops

• Published in: Hearing research 2005-04, Vol.202 (1-2), p.180-187
• Main Authors: Valk, W.L., Wit, H.P., Segenhout, J.M., Dijk, F., van der Want, J.J.L., Albers, F.W.J.
• Format: Article
• Language: English
• Subjects: Acute Disease; Animals; Biological and medical sciences; Cochlear Duct; Ear and associated structures. Auditory pathways and centers. Hearing. Vocal organ. Phonation. Sound production. Echolocation; Ear, auditive nerve, cochleovestibular tract, facial nerve: diseases, semeiology; Endolymph; Endolymphatic hydrops; Endolymphatic Hydrops - etiology; Endolymphatic Hydrops - pathology; Endolymphatic sac; Endolymphatic Sac - pathology; Female; Fundamental and applied biological sciences. Psychology; Guinea Pigs; Homogeneous substance; Medical sciences; Menière’s disease; Microinjections; Microscopy, Electron; Microspheres; Non tumoral diseases; Otorhinolaryngology. Stomatology; Time Factors; Vertebrates: nervous system and sense organs; Volume regulation
• ISSN: 0378-5955; 1878-5891
• DOI: 10.1016/j.heares.2004.10.010

The role of the endolymphatic sac (ES) in endolymph volume homeostasis is speculative. The present study investigates changes of the ES’s epithelia and luminal filling after induction of an acute endolymphatic hydrops. After microinjection of 1.1 μl artificial endolymph into scala media of the cochlea, guinea pigs were terminated immediately (n=6) or after different time intervals ; 1/2 h (n=3), 1 h (n=4) and 2 h (n=4). Inner ear specimens were processed for light and/or transmission electron microscopy. The non-injected contralateral ear served as a histological control. Correct injection was confirmed by detection of microspheres in the endolymphatic compartment after the same microinjection procedure. In all specimens, ribosome rich cells and intraluminal macrophages appeared to be actively involved in degradation of homogeneous substance (HS) by secreting lytic enzymes and digestion, respectively. Amazingly, in our study no ES differences were found between injected and non-injected ears and no distinct changes were observed in guinea pigs terminated after different time intervals. The ES’s luminal HS was always present and often to a large extent. This is in contrast with [Hear. Res. 138, 81] dramatic changes were observed. Endolymph volume homeostasis is a complex mechanism, in which the role of HS remains obscure.