Der Einflu� des chronischen Vitamin A-Mangels auf das Innenohr der Ratte

Abstract

Rats were fed a vitamin-A-free diet and the cochleas of these animals were studied under the light and electron microscope. The cochlear function was tested by means of the electrocochleography. No pathologic changes could be found in the organ of Corti; the stria vascularis and the cochleas showed normal development. The recordings of the deficient rats are identical in configuration to controls, but they are shifted to higher intensities due to an otitis media found in the tested animals. These findings suggest that vitamin A does not have an important function in the inner ear.

Progressive hearing loss in vitamin A-deficient mice which may be protected by the activation of cochlear melanocyte

“…In addition, the older VAD albino mice (16 weeks of age) exhibited neuronal loss in the spiral ganglion. The present findings that VAD mice develop hearing loss that progresses with age contradict the findings of some previous studies involving VAD mouse models, in which no significant hearing loss-induced morphological changes were observed after establishing a VAD diet 9 , 10 . These inconsistencies might stem from methodological differences between studies when establishing the VAD animal models.…”

“…These inconsistencies might stem from methodological differences between studies when establishing the VAD animal models. In previous studies, the animals were restricted to the VAD diet after birth 7 , 9 ; in contrast, we placed the animals on a VAD diet from 7 to 10 days of gestation. In order to achieve decreased plasma retinol concentrations, a vitamin A-free diet needs to last until the depletion of hepatic reserves.…”

“…However, the direct effect of VAD on hearing function remains controversial. A previous study reported no VAD-induced morphological changes in the cochlea of guinea pigs 8 , and another showed that vitamin A did not play an important role in the development, metabolism, and function of the rat cochlea 9 . Moreover, other studies have reported the presence of binding sites for vitamin A in the stria vascularis and high vitamin A levels in the whole cochlea of guinea pigs 10 .…”

“…These discrepant findings regarding the role of vitamin A in cochlear function appear to stem from genetic differences even within the same species, as well as differences in the methodology used for establishing VAD mouse models. In particular, one of the major limitations of previous studies was that VAD models were created by placing animals on a VAD diet from 2 to 3 weeks after birth, by which time, the plasma retinol concentrations could be maintained within a considerable range by the mobilisation of hepatic retinol reserves 7 , 9 , 11 .…”