Effect of Locally Applied Vitamin A and Estrogen on Rat Epidermis.

Vit A administered topically to the skin for 10 days resulted in an average increase, in epidermal thickness to about twice normal. A notable increase in the extent of the stratum granulosum occurred, and a decreased rate of keratin formation and/or an increased rate of keratohyalin formation are suggested. The effect was apparently entirely local; untreated skin areas from vitamin treated animals showed no significant alterations. Estrogen resulted in no observable change in the epidermis and did not counteract the stimulatory effect of the vitamin.