EFFECT OF FUMARIC-ACID, ITS DIMETHYLESTER, AND TOPICAL ANTIPSORIATIC DRUGS ON EPIDERMAL DIFFERENTIATION IN THE MOUSE TAIL MODEL

Fumaric acid, fumaric acid dimethylester, and the dithranol derivative C4-lactone were studied in the mouse tail test to evaluate their effe cts on epidermal cell differentiation compared with other topical anti psoriatic drugs, such as betamethasone, calcipotriol, and dithranol. M ouse tails were treated for 2 weeks and longitudinal histological sect ions prepared of the tail skin. The length of the orthokeratotic regio ns (stratum granulosum) was measured on 10 sequential scales per tail and expressed as percentage of the full length of the scale. In additi on, epidermal thickness was measured and the efficacy of the various c ompounds evaluated. In comparison to 2% salicylic acid ointment, all t ested compounds except fumaric acid significantly(p less than or equal to 0.05) increased the proportion of the orthokeratotic region. C4-la ctone and calcipotriol were less effective than dithranol, fumaric aci d dimethylester only moderately influenced cell differentiation, and b etamethasone showed the least potent effect. Dithranol was the most po tent substance inducing orthokeratosis without increasing epidermal th ickness.