The effect of excess vitamin A on the oesophageal epithelium of late foetal rats has been studied in organ culture.
In explants kept in normal medium the epithelium is, at first, higher and the keratinisation increased as compared with the development of the organ in vivo. At the later stages of growth, the acceleration of keratinisation leads to an extreme thinning of the epithelium.
Excess vitamin A completely inhibits keratinisation and induces a transformation of the cells lining the oesophageal lumen into mucin-secreting elements. In vitamin A-treated cultures the epithelium remains high throughout the whole period of cultivation.
The amount of secretory matter and the height of the epithelium seem to depend on an adequate supply of oxygen and carbon dioxide to the cells.