Mucous metaplasia of the hamster cheek pouch epithelium under hypervitaminosis A

Abstract

Mucous metaplasia of the hamster cheek pouch epithelium induced by implantation of vitamin A pellet was studied electron microscopically. After 5-10 days of vitamin A treatment, the epithelium was devoid of stratum corneum, and often infiltrated with inflammatory cells. The intercellular spaces were wide, and membrane coating granules underwent modifications believed to be the earliest signs of mucous production. After 15 days of vitamin A treatment the inflammation had largely gone, and the epithelium was made up of several layers of cuboidal cells. The intercellular spaces and keratin fibrils had greatly decreased. Some mucous granules appeared for the first time in the cuboidal superficial cells. Various other changes in the cheek pouch epithelium were observed in animals treated with vitamin A for 20-25 days. In some regions hyperplasia or inflammatory reactions were observed, whereas in other regions complete mucous metaplasia was found. In completely metaplastic regions a surface layer of typical mucous cells was seen lying at the top two or three layers of cuboidal cells.