| The inner ear is responsible for the mechano-electrical transduction of sound and the forces of acceleration involved in the sensation of balance and head position. In order for transduction to occur, the extracellular environment of the inner ear must be in homeostasis. This environment is comprised of fluids which contain ions and macromolecules. The ionic composition of the inner ear fluids has been extensively studied, however only in recent years have investigators begun to examine what role complex, non-ionic macromolecules play in maintaining inner ear homeostasis.; The glycosaminoglycans (GAGs) are one such family of macromolecules that have been investigated in the ear primarily as constituents of a specialized region of the endolymphatic duct-system, the endolymphatic sac. Presence of the unsulfated GAG hyaluronic acid (HA) and several classes of sulfated GAGs has been established in the endolymphatic sac, but only HA has been studied within the rest of the inner ear fluid system. Sulfated GAGs have been found in every fluid system of the body examined thus far. The sulfated GAGs keratan sulfate (KS) and chondroitin sulfate 4,6 (CS) have already been demonstrated in inner ear tissue and their physiology appears to be affected in disease states in other systems of the body. This alteration is a result of complex factors that are currently under investigation, and is thought to involve low oxygen tension. It is also known that CS is a free radical scavenger whereas KS is not and this factor may contribute to the extent of damage seen in diseased tissue. It is likely that CS and KS are present in normal inner ear fluids and their distributions differ.; New histologic techniques were developed for this study in order to determine the presence of GAGs within the inner ear fluids. The distribution of the individual classes of GAGs, CS 4,6 and KS was also investigated as their distributions differ and their physiology appears to be interconnected in other tissues. The findings of this study confirm the hypothesis that CS and KS are present within inner ear fluids beyond the endolymphatic sac and their patterns of distribution differ. Preliminary results of KS labeling in ears with surgically induced endolymphatic hydrops suggest that the distribution of at least one of these GAGs is altered in the diseased inner ear. |
