PHYSIOLOGICAL SIGNIFICANCE OF POTASSIUM ION IN ENDOLYMPH

Abstract

According to Smith et al., the potassium concentration in the endolymph is 30 times higher than that of the perilymph and cerebrospinal fluid.Sodium concentration is only a tenth of that in the perilymph or cerebrospinal fluid.Chlorine in the endolymph is 90% of that in the peri- lymph or cerebrospinal fluid.All three are low in protein.Among those results obtained by them, the unusually high potassium concentration of the endolymph should be mentioned as the most striking evidence.However the physiological role of this characteristic chemical composition of the endolymph -remained obscure until today.The contribution done by them suggests a new attempt, that is the experimental observation of symptoms in guinea pigs induced by replacement of endolymph with various fluids, considering also in its relation to the pathological condition of unknown origin of so called Meniere's syndrome.As a preliminary study, the methods of replacement were studied and the responses induced by replacement with artificial endolymph were observed.The results were as follows:1.The inner ear was exposed by surgical operation and a small hole of 100u in diameter was opend into the membranous canal of the cochlea and of the vestibular canal under a binocular microscope.The apparatus for replacment consists of glass tube measuring 1 mm diameter and 25 cm in length, a rubber tube connected with one end of glass tube, a cock set on the middle of rubber tube and a fine injecting needle on the other end of rubber tube.The artificial endolymph warmed to the body temperature of the animal and injected into the endolymph system with the apparatus through one hole under pressure and the fluid passed through the endolymphatic duct and streamed out from the another hole.Thus the replacement of the endolymph with artificial endolymph was performed.After the replacement of the endolymph, methylene blue was injected into the endolymph system under the same procedure and the inner ear was dissected under a microscope for the purp- ose of ascertaining the replacement of the endolymph with artificial endolymph.And for the same purpose the histological examination was performed.Thus the method of replacement was eastablished.2 The pressure of 5 cm H2O was most suitable for the replacement of endolymph.Applying this pressure, the mechanical stimulation to vestibular organ, induced by water pressure, was reduced remarkably and the replacement could be performed thoroughly without any recognizable sign except a few twitch of the eye in the inital stage of the infusion.3 The replacement of the unilateral endolymph with the artificial endolymph, contains 140 mEq/L potassium, exerted no recognizable effect on the animals.No changes were observed on the eye, posture, movement, EMG-activity of the skeletal muscles, respiration, blood pressure and ECG-activity of the animal.According to these results, this method was considered as a suitable method in the study of the physiological significance of the endolymph by the replacement of the endolymph with vario- us solutions.