Localization of vitamin a by autofluorescence during induced metaplastic changes in cultures of skin

Summary A technique was devised for following the uptake and location of vitamin A in organ cultures. Explants of 12- and 13-day embryonic mouse upper lip skin were grown for 3,6 or 9 days in biological medium to which was added 0,4.1 or 6.9 μg per ml of retinyl acetate. This form of vitamin A caused glandular morphogenesis of vibrissa follicles, and keratinization in epidermis and follicles was completely suppressed in 12-day explants and partially suppressed in 13-day explants. Frozen sections at 16 μm showed the white, non-fading fluorescence of keratin and the green, rapidly-fading fluorescence due to vitamin A which was captured by high-speed photography. Although more concentrated within lipid droplets in the dermis, the vitamin penetrated both the epidermis and the hair follicles. The ability to obtain permanent photographic records of the fading fluorescence makes this a useful method for analyzing vitamin A distribution as well as keratin distribution. This work was supported by the National Research Council of Canada (Operating Grant to M. H. Hardy and Postgraduate Scholarship to R. Van Exan) and by the Ontario Ministry of Agriculture and Food.