Abstract
From chemical analyses of inner ear fluids, it was found that the sum concentration of electrolytes (Na+K+Cl) is higher in the endolymph than in the perilymph and that the perilymph contains a higher concentration of glucose and protein compared to the endolymph. These findings are discussed from the viewpoint of osmotic equilibrium between the endolymph and the perilymph. Considering our previous experiments and other literature, homeostatic regulation may operate in the endolymph to maintain constant chemical composition. The perilymph, on the other hand, can be regarded as an interstitial space fluid, being susceptible to systemic changes in the chemical concentration in the blood. This may imply that there is biological significance in developing osmotic imbalance between the endolymph and perilymph. Recently, some experimental works have been directed to the study of osmotic agents which are currently applied for diagnosis and treatment of endolymphatic hydrops.
On reviewing the above experimental results including our findings, there is discussion of the relationships of fluid dynamics in inner ear fluids among electrolyte concentrations, osmotic pressure and fluid pressure.
Although the endolymphatic system is not directly influenced by systemic change in the serum concentration and by the hemodynamics, some substances are thought to have their sites of action in the stria vascularis. As such substances, aldosteron, amphotericin B, vasopressin, ouabain and diuretics are cited. These substances are supposed to affect the electrolyte transport system in the stria vascularis or in other membrane of the inner ear. Using these substances in experimental study, the mechanism of high potassium in the endolymph and the mechanism of the regulation of the osmotic pressure between the endolymph and perilymph should be clarified in the future.
