Therapy with a synthetic retinoid--(Ro 10-1670) etretin--increases the cellular retinoic acid-binding protein in nonlesional psoriatic skin.

Cellular retinol (CRBP)-and retinoic acid (CRABP)-binding proteins were determined in samples of lesional and nonlesional skin of psoriatic patients, before and during oral administration of a synthetic retinoid, Etretin (Ro 10-1670). A 200% increase in CRABP levels, measured by the ability of the protein to bind retinoic acid, was observed in the normal skin during treatment. The CRBP levels were not altered during therapy. The results show that CRBP and CRABP are independently regulated in human skin and suggest that synthetic retinoids may exert their pharmacologic effects by interfering with the regulation of natural retinoic acid receptors.