A Morphological and Histochemical Study of the Effect of Urea on Experimental Endolymphatic Hydrops in Guinea Pigs

Abstract

The present study was performed to elucidate the effect of urea administration on the inner ear lesion in the patient with Meniere's disease. Urea (2g/kg) was given orally to the Hartley guinea pigs which had undergone obliteration operation of the endolymphatic duct on the right side according to Kimura (1967) one and three weeks previously. The animals were sacrificed for staining of the superficial blood vessels of the endolymphatic space by the benzidin reaction and for demonstration of the activity in the energy metabolism of the inner ear hair cells by the supravital reduction reaction with nitro-BT. The following results were obtained.
1. One week after the operation, scattered stenotic or ischemic foci were found in the capillary net-work subjacent to the vestibular sensory organs, such as cristae ampullares and maculae and in that of the stria vascularis of the right ear which received the operation. These capillary changes were more prominent in the basal turn, especially in its lower part rather than in the second turn.
2. Three weeks after the operation, slight decrease in formazan deposition was seen in the outer hair cells, especially severe in the apical turn, resulting in scattered loss of the outer and inner hair cells in the right ear which received the operation.
3. The urea treatment induced repair of the capillary changes of the inner ear and alleviation of the impairment of formazan deposition to the outer hair cells in the right ear.
4. The mechanism of the effect of urea on the endolymphatic hydrops and associated changes of the inner ear was discussed.