Differentially localized incorporation of amino acids in relation to epidermal keratinization in the newborn rat

Abstract

Abstract Incorporation of tritiated methionine, phenylalanine, leucine, glycine and histidine into protein in the epidermis of the newborn rat was studied by autoradiography. Methionine, phenylalanine and leucine behaved similarly. Thirty minutes after injection, radioactivity was detected in both nucleus and cytoplasm of the basal, spinous and granular cells with a greater intensity over the cells of the lower layer as compared with that observed over the upper layer. The label appeared over the cornified cells at 24 hours after injection probably as a result of the migration of cells into the cornified layer. In the case of glycine and histidine, the label was detected in eachof the three layers at 30 minutes after injection but the labeling was higher in the upper part of the epidermis as compared with the lower part. The label appeared in the cornified layer six hours after injection. Processes possibly involved in formation of the cornified layer are discussed.