The Effects of Vitamin A and Citral on Epithelial Differentiation in vitro 1. The Chick Tracheal Epithelium

Abstract

ABSTRACT Differentiation of the tracheal epithelium of embryonic chicks was studied in organ cultures in a normal medium and in media containing added vitamin A and citral. In normal medium, the tracheal epithelium differentiated well, but usually fewer mucous cells developed than in the intact chick. High concentrations of vitamin A alcohol inhibited the differentiation of mucous cells and favoured that of ciliated cells. Citral, in fairly low concentrations, had opposite effects: it stimulated mucus-secretion and inhibited the differentiation of ciliated cells. In higher concentrations it stimulated division of the basal cells, and the epithelium became stratified and sometimes keratinized. Vitamin A and citral added together to the culture medium produced a citral effect, which varied in intensity according to the proportions of the two compounds, but was always milder than that resulting from treatment with the same concentration of citral alone. These results suggest that citral inhibits both the natural vitamin A in the plasma and the added synthetic vitamin A, thus producing changes in the tracheal epithelium characteristic of vitamin A deficiency. The results indicate that secretion of mucus by the tracheal epithelium is maximal at a lower concentration of vitamin A than that to which it is normally exposed in the body. It is suggested that vitamin A may influence epithelial differentiation partly by affecting the mitotic rate.