Embryonic and postnatal accumulation of homogeneous substance in the endolymphatic sac in the guinea pig

• Published in: Auris, nasus, larynx nasus, larynx, 2000, Vol.27 (1), p.3-8
• Main Authors: Erwall, Claes, Friberg, Ulla, Rask-Andersen, Helge
• Format: Article
• Language: English
• Subjects: Animals; Animals, Newborn; Contrast Media - pharmacokinetics; Ear, Inner - embryology; Ear, Inner - growth & development; Endolymphatic sac; Endolymphatic Sac - chemistry; Endolymphatic Sac - embryology; Endolymphatic Sac - ultrastructure; Female; Fluorescein - pharmacokinetics; Gestational Age; Guinea Pigs; Hearing; Hearing - physiology; Hyaluronic Acid - analysis; Hyaluronic Acid - metabolism; Inner ear; Microscopy, Electron - methods; Morphology; Oligosaccharides - analysis; Oligosaccharides - metabolism; Pregnancy; Staining and Labeling - methods
• ISSN: 0385-8146; 1879-1476
• DOI: 10.1016/S0385-8146(99)00041-3

Objective: The endolymphatic sac (ES) of vertebrates contains varying amounts of a homogeneous substance (HS) that stains deeply with basic aniline dyes. Histochemically, HS is characterized as a carbohydrate–protein complex, being both neutral and acidic in nature. In the present study, deposition of HS in the ES was studied in the guinea pig from the 3rd week of gestation to 104 weeks postnatally in order to find out if HS accumulates with age, at which point during embryonic development this substance appears, if its presence is correlated to the sense of hearing and if the amount of substance in the left versus right ear of one and the same animal is correlated to any degree. Methods: Sixty-nine endolymphatic sacs were evaluated in 38 guinea pigs. The ES specimens were sectioned for light and transmission electron microscopy and the amount of HS filling was categorized in four groups: none, low, medium and a high level of substance. Results: The substance was not discerned until after 7 weeks of gestation, when it filled only a minor part of the distal ES lumen. At 9 weeks gestation the nature of the substance altered, becoming homogeneous, as visualized by osmium–toluidine blue staining and approximately filling the distal half of the luminal space. In the postnatal period, 65% of ES specimens were filled with HS to the intermediate or proximal ES, whereas only 6.5% of the ES specimens were devoid of the substance. The extent of filling of the ES in the prenatal temporal bones was significantly less than postnatally ( P