The influence of hydrocortisone on the metaplastic action of vitamin A on the epidermis of embryonic chicken skin in organ culture.

INTRODUCTION I N earlier work it was found that the addition of excess of vitamin A (10 i.u./ml.) to the culture medium produces drastic changes in embryonic limb-bones and skin in organ culture. The matrix of cartilage (mouse, chick) and bone (mouse) rapidly disappears (Fell & Mellanby, 1952; Fell, Mellanby, & Pelc, 1956) and in the epidermis of skin from 7 to 18-day chick embryos (Fell & Mellanby, 1953; Fell, 1957; Pelc & Fell, 1960) keratinization is immediately arrested and a remarkable mucous metaplasia appears. In a previous paper (Fell & Thomas, 1961) it was shown that when hydrocortisone (7-5 /Ag./ml.) is added together with vitamin A, resorption of intercellular material is greatly retarded in the explanted limb-bone rudiments. The present experiments were undertaken to see whether the hormone would also inhibit the metaplastic effect produced by vitamin A in the epidermis of embryonic chicken skin in vitro. A mutual antagonism between the two agents in their action on the epidermis has been demonstrated, and is described below.