Effect of Hydrocortisone on the Skin of the Developing Chick Embryo

Hydrocortisone treatment of chick embryos caused acceleration of epidermis thickening and keratinization, decrease in dermal cell number and increase of dermal collagenous fibres. The hormone also caused a marked increase of some protein fractions with low mobility and also decreased acid and alkaline phosphatase activity. INTRODUCTION Avian skin was described in detail (Fell, 1962; Mottet and Jensen, 1968 and Demarchez et a/., 1984 ) and feather development was extensively studied histologically (Fell, 1962; Wessells, 1965; Garber, 1967; Garber and Moscona, 1967; Bellairs, 1971; Haake eta/., 1984 and Mayerson and Fallon, 1985) and ultrastructurally ( Kischer, 1963; Kallman eta/. 1967; Wessells and Evans, 1986 and Haake and Sawyer, 1982 ). Hydrocortisone was found to accelerate skin keratinization in vivo ( Stuart eta/., 1972 and Demarchez et a/., 1984 ) and in vitro ( Fell, 1962; Sugimoto and Endo, 1969; Sugimoto eta/., 1974 and Kojima eta/., 1976) and also to inhibit normal feather development in vivo ( Stuart eta/., 1972 and Demarchez eta/., 1984 ) or in vitro (Fell, 1962; Sugimoto and Endo, 1969; Sugimoto eta/., 1974; Kojima eta/., 1976 ). Electrophoretic studies of solubilized epidermal proteins revealed two distinct protein groups, SCMEpA and SCMEpB, in which the former was selectively accumulated during hydrocortisone-induced keratinization in vitro (Sugimoto eta/., 1974; Kojima eta/., 1976 ). Johnson and Bevelander ( 1947) reported that alkaline phosphatase was present in the mesoderm throughout the development of the feather and appeared in the ectoderm only at later stages. Alkaline phosphatase detected in the cells of developing feather pulp was more reactive than that of the epidermal cells (Hinsch, 1960 ). Effect of hydrocortisone on skin ..... The present work investigates the effect of hydrocortisone on ( a ) embryonic chick skin and feather, and ( b ) on souluble protein content and acid and alkaline phosphatase activity during skin development. MATERIALS AND METHODS Fertilized eggs of the Egyptian domestic fowel, Gallus domisticus, were incubated at 38°C and about 70% relative humidity and turned 2 to 4 times daily. The embryos were staged according to Hamburger and Hamilton ( 1951 ) criteria. After 6 days of incubation, a single dose of 0.1 mg hydrocortisone 21-sodium succinate (Sigma) in 0.1 ml of 10% sterile Tyrode's solution was deposited on the chorioallantoic membrane. A control egg group was similarly injected with 0.1 ml of sterile Tyrode's solution and a third group was untreated. The dorsal skins 10-,12and 15-day control and hydrocortisone-treated chick embryos were examined.