Abstract
Thirteen-day chick embryo shank skin was cultured for 4 days by the ‘Millipore’ filter-roller-tube method in a chemically defined medium, BGJb supplemented with ascorbate. Hydrocortisone was added into the medium at a concentration of 0.01μg/ml. The epidermis of control explants showing no sign of keratinization and that of hydrocortisone-treated explants covered with heavily cornified layers were examined for specific keratinous proteins (S-carboxymethyl epidermal proteins: SCMEp) with use of polyacrylamide disc electrophoresis.
SCMEp was prepared by treating the epidermis homogenate in 8 M urea first with 2-mercaptoethanol and secondly with monoiodoacetic acid. Supernatant of the reduced, carboxymethylated homogenate was electrophoresed with polyacrylamide gels containing 8 M urea in the presence or absence of sodium dodecyl sulfate.
When compared with the epidermis of embryonal and neonatal chicks in the normal course of development, SCMEp from control explants gave all the same electrophoretic pattern as that of younger embryos having no horny layer yet, whereas in some parts SCMEp from hydrocortisone-treated explants showed the highly advanced pattern as seen in older embryos and neonatal chicks.
These findings indicated that in the chick embryonic skin growing in vitro hydrocortisone selectively accelerated the synthesis of limited parts of the specific proteins to induce morphological keratinization of epidermal cells.
