title: Vitamin A and beta-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 (beta-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 beta-carotene by reversed phase high-performance liquid chromatography. The highest retinol concentration (0.8 micrograms/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 beta-carotene (1.0 micrograms/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.
mesh_terms: D000818:Animals; D002338:Carotenoids / Q000032:analysis*; D002417:Cattle; D004817:Epidermis / Q000032:analysis*; D007633:Keratins; D009666:Nose / Q000166:cytology; D014801:Vitamin A / Q000032:analysis*; D019207:beta Carotene
chemical_list: D019207:beta Carotene; D014801:Vitamin A; D002338:Carotenoids; D007633:Keratins