Funktionelle und morphologische Befunde nach einem chronischen Vitamin-A-Mangel bei jungen Ratten

Zusammenfassung

Es wurde bei Ratten ein prä-, peri- und postnataler Vitamin-A-Mangel erzeugt. Gegenüber den Kontrollen zeigten die Mangeltiere eine verzögerte Reifung und irreversible Schädigung des vestibulären Systems. Eine frühe Repletion mit Vitamin A normalisierte die Funktion, eine späte dagegen nicht mehr. In den morphologischen Untersuchungen fand sich eine Knochenapposition in der Labyrinthkapsel und im Modiolus sowie elektronenmikroskopisch dystrophe Veränderungen im Corti-Organ und im Ganglion spirale cochleae. Vitamin-A-Mangel schädigt im wachsenden Organismus die Entwicklung des Labyrinthes.

Summary

Pregnant rats were fed a vitamin A-depleted diet. After weaning, 40 litters (10 controls, 30 experimental) were divided into eight groups, four female and four male. All groups were given the same diet. The control groups (male and female) received 100 IU vitamin A/day, the deficient groups only a maintenance dose of 1-2 IU vitamin A/day. One female and one male group were repleted with vitamin A after the 27th day of life and two further groups of both sexes were repleted after the 49th day of life. After the 23th day of life all litters were trained for the Rail Test and after the 27th day the time on the rotating bar was recorded. After the 15th week all the animals were anesthetized and decapitated and the cochleas prepared for histologic and electronmicroscopic examinations. - The vitamin A-deficient animals displayed delayed development of the visual, auditory, vestibular and motor systems in both sexes. Early repletion with vitamin A after the 27th day of life normalized the motor and vestibular systems to normal in the experimental animals. Late repletion with vitamin A, after the 49th day, does not normalize function in the Rail Test. In histologic studies some of the experimental animals showed displasia of the bony and membranous labyrinths. Others had signs of degeneration of the organ of Corti and the spiral ganglion of the cochlea. In the electron-microscopic studies an accumulation of lysosomes in the sensory cells and supporting cells, and dystrophic neuronal fibers and ganglion cells were found in the spiral ganglions of the vitamin A-deficient groups and to a lesser extend also in the groups with late repletion. In the control groups and in the groups with early vitamin A repletion there was no morphological damage. The results of these experiments support the authors' hypothesis that vitamin A is important for the development and function of the labyrinth.