The Influence of Hydrocortisone on the Metaplastic Action of Vitamin A on the Epidermis of Embryonic Chicken Skin in Organ Culture

Abstract

The effects of hydrocortisone, vitamin A, and both agents together were compared in explants of skin from 9-day chick embryos grown in organ culture. In normal medium the periderm degenerated and was shed in the usual way. The epidermis differentiated and keratinized more rapidly than in the embryo; the feather germs differentiated into sheath and barb rudiments and keratinized, after which development ceased. Hydrocortisone alone caused extreme dilation of the peridermal cells which later were sloughed. The differentiation of the epidermis was much accelerated as compared with that of controls in normal medium. The feather germs aborted at an early stage, probably owing to precocious histological differentiation. With vitamin A alone the peridermal cells actively secreted mucus and many formed cilia-like processes; the periderm formed an integral part of the epithelium. In the epidermis keratinization was suppressed and mucous cells differentiated. The feathers remained almost unchanged; the epithelium failed to keratinize and often became secretory. In explants exposed to both agents together, during the first 2 days the periderm secreted copiously a dense, viscid substance the nature of which was unknown, but which appeared to contain both keratinous and mucous material; a similar secretion was sometimes produced by the epidermis at a later stage when the concentration of added vitamin A was low (5 i.u./ml.). The hormone and the vitamin were mutually antagonistic in their action on the epidermis. At first the hydrocortisone prevailed, and large areas of the epithelium often became squamous and keratinized; later the vitamin predominated, the keratin was sloughed, and mucous cells were formed. In two days, feather germs exposed to both agents at once, swelled to several times their original size. Changes like those produced by the hormone and vitamin together appeared in explants grown for 8 days in the presence of vitamin A and then transferred to medium containing hydrocortisone, but not in skin pretreated with the vitamin and then placed in normal medium. These effects were not seen in skin transplanted from medium with hydrocortisone to one containing vitamin A; the epidermis showed the usual changes produced by vitamin A alone.