Vitamin A and β-Carotene Concentrations at Different Depths of the Epidermis: A Preliminary Study in the Cow Snout

Abstract

Vitamin A (retinol) is an anti-keratinizing agent essential for normal epithelial differentiation. In order to examine the epidermal distribution of vitamin A and provitamin A (i3-carotene), we took advantage of the extraordinarily thick snout epidermis of the cow which can be cut horizontally into at least 6 layers, representing keratinocytes at different stages of maturation. Extracts of saponified samples were analyzed for retinol and @-carotene by reversed phase high-performance liquid chromatography. The highest retinol concentration (0.8 pg/g protein; n=3) was recorded closest to the dermis; progressively decreasing amounts of retinol were found in the upper parts of epidermis. Maximum values of @-carotene (1.0 Kgg/g; n=7) were found in the lower parts of epidermis; substantially lower levels were seen at the dermal transition zone and in the upper parts of epidermis. The results suggest that the endogenous concentration of vitamin A in snout epidermis is inversely related to the degree of cellular differentiation.

Expression of Keratin K2e in Cutaneous and Oral Lesions

“…A gradient of retinoic acid with the highest level in the basal layer and declining to much lower levels in suprabasal layers has been proposed in epidermis. 62 This would potentially suppress K2e gene expression in lower suprabasal layers.…”