[Formation of the inner ear lymphs. Permeability of inner ear membranes (author's transl)].Arch Otorhinolaryngol. 1976 Sep 16; 212(4):219-29.AO
1. The endolymphatic system is morphologically a close system. The inner surface of the wall is tightly lined with an epithelium of ectodermal origin. The perilymphatic spaces are enlarged intercellular spaces which are built from the embryonic mesenchyme. 2. The perilymph ist an ultrafiltrate of plasma. There is probably a flow from the cerebrospinal fluid which is constantly renewed. The diffusion in the perilymph is dependent on the concentration and the size of the molecules. The endolymph is mainly a perilymph-filtrate. The "secretory" epithelia (e.g. stria vascularis cells and other tissues) of the endolymphatic system perform an important role to sustain the potassium and sodium concentrations. The ionic concentrations regulate the water movement also the volume of the endolymphatic spaces. They are maintained by anoxy-sensitive pumps. 3. The DC potential within the endolymphatic spaces represents the movement of certain electrical charge through membranes. By applying various inhibitors it is possible to distinguish the pumping mechanisms, and to observe the continuous changes of potassium and sodium concentrations with Na+ specific electrodes and K+ specific electrodes. There are probably three interdependent sources of driving-forces: a. A positively electrogenic K+-pump which is anoxia-sensitive and can be inhibited by Ethacrynic acid. This mechanism is more active in stria cells and less so in utricle and saccule. b. A negatively electrogenic Na+-K+ exchange-pump in all parts of the endolymphatic spaces is inhibited by Ouabain or anoxia. c. The passive diffusion of potassium-ions from endolymph to perilymph results an electro-negative effect.