Biological comparison of isomers and chemical forms of vitamin A (retinol)

The effects were comparcd on mouse tail scale epidermis of vitamin A acid, acetate and alcohol (all as the trans isomer) and the cis aldehyde by regular topical applications. Increases in epidermal thickness produced by different doses were compared statistically, and the induction of a granular layer and of epidermal alkaline phosphatase activity was demonstrated. The different forms and isomers of vitamin A have similar effects on the epidermis, but vary individually in activity, Retinoic acid and trans‐retinyl acetate were very similar in their action when used in a water solubilizing vehicle. The fact that retinyl acetate is very much cheaper than retinoic acid is a point in favour of its use for the treatment of psoriasis.