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

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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 (β-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 β-carotene by reversed phase high-performance liquid chromatography. The highest retinol concentration (0.8 μg/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 β-carotene (1.0 μg/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.