EXPERIMENTAL STUDY OF THE INNER EAR DAMAGE IN NEPHROTIC SYNDROME

Abstract

Although the inner ear is the organ different from the kidney, it has been thought, for a long time, that the malformation of the inner ear is associated with that of the kidney, that the inner ear damage is related to the renal damage which is induced by the administration of aminoglycoside antibiotics, and recently that there is some relation between the kidney and the inner ear in the auditory disorder and equilibrium disturbance of the patients with hemodialysis.
The administration of puromycin aminonucleoside (PAN) to rats can give rise to a pathosis like lipoid nephrosis. It remains to be solved, however, what change in the inner ear is caused by its administration at the time. In view of the fact, an attempt has been made to examine not only the state of the inner ear of a living body with nephrotic syndrome but also the timehonored problematic relation between the kidney and the inner ear. In respect to the auditory disorder, observations were made on Preyer's reflex and auditory brainstem response (ABR), and further, the morphological observations of the inner ear were made by the use of a light microscope and scanning and transmission electron microscopes. In addition, for the purpose of observing the changes in the blood-cochlea barrier, a tracer study was tried by means of horseradish peroxidase (HRP) and iron dextran. As a result, the following observations were obtained.
1. No significant difference between normal rats and rats with nephrotic syndrome in the threshold of Preyer's reflex and ABR determination was noted.
2. In the cochlea, a main change was noted in the stria vascularis which is said to be similar to the nephron, as follows.
(1) The changes of element in the basement membrane of the capillary of stria vascularis.
(2) A remarkable swelling of the intermediate cells.
(3) Changes in the cytoplasma near the free surface of the marginal cells; vacuolization; a remarkable increase in lysosome; severance in the plasma membrane; and the physically pressed picture induced by the swelling of the intermediate cells.
3. When HRP was intravenously injected as a tracer, the infiltration of HRP into the intercellular spaces through the capillary lumens of the stria vascularis in normal cases was observed but the infiltration of HRP to the endolymphatic spaces was not observed. In the cases with nephrotic syndrome, the infiltration of HRP from the marginal cells to the endolymphatic space was noticed. In other words, it was demonstrated that the function of the stria vascularis changes and consequently the endolymphatic composition changes.
4. While the change in the maculae was slight in the vestibule, a remarkable vacuolization was seen in the Type I hair cell.
The above-mentioned results suggest that a living body showing nephrotic syndrome could have auditory and vestibular disturbance.