A rapid and simple test system for the evaluation of the inhibitory activity of retinoids on induced ornithine decarboxylase activity in the hairless rat epidermis.

In mouse skin, antiproliferative agents including retinoids inhibit induction of ornithine decarboxylase activity by a variety of hyperproliferative stimuli. In the hairless rat skin, ornithine decarboxylase activity was induced by ten successive strippings with cellotape and by topical application of 12-O-tetradecanoyl-phorbol-13-acetate. Topical application of all trans-retinoic acid (25 nmol/cm2) immediately after the tape stripping of the skin significantly inhibited the induction of ornithine decarboxylase activity at all time points measured. The inhibition by all trans-retinoic acid of ornithine decarboxylase induced by cellotape stripping was dose dependent as was found to be the case for arotinoid, retinol, Ro-10-1670, motretinid, 13-cis-retinoic acid, etretinate, and vitamin A. Oral administration of all trans-retinoic acid also inhibited the ornithine decarboxylase activity induced by cellotape stripping. We propose the assay of ornithine decarboxylase activity in the hairless rat epidermis after tape stripping for a rapid evaluation of new retinoids.