Epidermal Kinetics and Skin Condition: I. Stripping Technique for Quantitating Stratum Corneum Turnover in Hairless Mouse Skin

Abstract

The turnover kinetics of hairless mouse epidermis were explored. ³H-labeled lysine was incorporated into epidermal proteins by injecting it systemically through the tail vein. Radioactivity in the outermost layer of stratum corneum was initially documented by stripping the skin daily with cellophane tape and assaying the tissue adhering to the tape. A broad band of radioactivity was detected between 4 and 7 days, indicating that lysine labels proteins throughout the forming epidermis. To ensure that stripping did not accentuate turnover, stripping was also performed every third day per mouse on rotation through three groups of radiotagged mice. Although there was more variability in the data gathered this way, the curves for daily stripping and every third day stripping actually superimposed. [³H]Glycine was introduced as the marker. This amino acid evidenced a single radioactive peak coinciding in time with the first lysine peak. The mass of stripped cells on each tape was quantified using a sensitive balance. A polyester tape, which removed approximately 30 μg tissue/cm², was suited to this purpose. Radioactivity in terms of activity per mass (specific activity) peaked between 3 and 5 days. When the cumulative specific radioactivity was plotted against time, sigmoidal curves were obtained, with inflection points indicating that the abdominal and dorsal turnover times of hairless mouse stratum corneum are 3.5 days and 4.1 days, respectively.