Histochemical evidence of mucosubstances in the metaplastic epidermis and hair follicles produced in vitro in the presence of excess vitamin A

Pieces of upper lip and lower jaw from 13‐day old mouse embryos grown in organ culture with excess vitamin A showed metaplastic changes in epidermis and hair follicles after 7 to 21 days. Changes were less marked in upper lip explants from 15‐day old embryos. Areas of keratinizing epidermis showed a much higher incidence of Alcian blue‐positive bodies when excess vitamin A was present. Histochemical tests with Alcian blue at critical electrolyte concentrations indicated moderately sulfated acidic mucosubstances in these bodies. Other patches of epidermis were transformed into stratified cuboidal epithelium producing PAS‐positive. Alcian blue‐negative, mucosubstances. The hair follicles, transformed by vitamin A into glands, developed three types of epithelium with apical granules, luminal borders and occasional goblet cells, all showing mucosubstances. Tests suggest that both metaplastic epidermis and glands secrete either neutral mucosubstances or non‐sulfated acidic mucosubstances. Another response to vitamin A was a rapid loss of glycogen, particularly in hair follicles and the epidermal basal layer. It was concluded that excess vitamin A alters not only the morphogenesis but also the distribution and synthesis of polysaccharides in developing skin.