A Rapid and Simple Test System for the Evaluation of Inhibitory Activity of Retinoids on Induced Ornithine Decarboxylase Activity in the Hairless Rat Epidermis MARTINE BOUCLIER, BRAHAM SHROOT, JACQUES EUSTACHE, AND CHRISTOPHER N. HENSBY In zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA mouse skin, a ntip ro life ra tive a g e nts inc lud ing re tino id s inhib it ind uc tio n of o rnithine d e c a rb o xyla se a c tivity by a variety o f hyp e rp ro life ra tive stim uli. In the ha irle ss ra t skin, o rnithine d e c a rb o xyla se a c tivity w a s ind uc e d b y te n suc c e ssive strip p ing s w ith c e llo ta p e and by topical a p p lic a tio n o f 12-O -te tra d e c a no yl-p ho r- b o l-13-a c e ta te . To pic a l a p p lic a tio n o f a ll tra ns-re tino ic a c id (25 nmo l/ c m2) im - m e d ia te ly a fte r the ta p e strip p ing o f the skin sig nific a ntly inhib ite d the ind uc tio n o f o rnithine d e c a rb o xyla se a c tivity a t a ll tim e p o ints m e a sure d . The inhib itio n by a ll tra ns-re tino ic a c id o f o rnithine d e c a rb o xyla se ind uc e d b y c e llo ta p e strip p ing w a s d o se dependent as was found to be the case for a ro tino id , re tino l, Ro -lO - 1670, m o tre tinid , 13-c is-re tino ic a c id , e tre tina te , and vitamin A. O ra l a d m inistra - tio n o f a ll tra ns-re tino ic a c id a lso inhib ite d the o rnithine d e c a rb o xyla se a c tivity ind uc e d b y c e llo ta p e strip p ing . We propose the a ssa y o f o rnithine d e c a rb o xyla se a c tivity in the ha irle ss ra t e p id e rmis a fte r ta p e strip p ing fo r a ra p id e va lua tio n of ne w re tino id s. Key Words: Re tino id s; O rnithine d e c a rb o xyla se a c tivity; Ep id e rmis INTRODUCTION Our inte re sts in skin p ha rm a c o lo g y led us to develop animal models to study the biological effect of topical application of various drugs used in dermatology. Retinoids, the family of molecules comprising both the natural and the synthetic analogues of vitamin A, are potent agents controlling cellular differentiation and proliferation (Sporn and Roberts, 1983). They have anticarcinogenic and antiproli- ferative properties (Elias and Williams, 1981; Voorhees, 1979). Recently, they have been shown to be of value as therapeutic agents for the treatment of skin diseases such as psoriasis, acne, and potential skin cancer (Sporn et al., 1980). The polyamines, putrescine, spermidine, and spermine are intimately involved in cellular growth and proliferation processes (Pegg and McCann, 1982). In the skin, the induction of the rate-limiting polyamine biosynthesis enzyme, ornithine de- Fro m the C e ntre Inte rna tio na l d e Re c he rc he s De rm a to lo g iq ue s (C.I.R.D.) Sophia-Antipolis, 06565 Val- bonne Ckdex, France. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Addre ss re p rint re q ue sts to : Dr. M. Bouclier, Center International de Recherches Dermatologiques, Sophia-Antipolis, 06565 Valbonne Cbdex, France. Received September, 1985; revised and accepted November, 1985. 151 Journal zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA o f Pha rm a c o lo g ic a l Methods 16, 151-160 (19@6) 0 1986 Elsevier Sc ie nc e Pub lishing Co., Inc., 52 Vanderbilt Avenue, New York, NV lW17 016&i402/86/$03.50