THE INDUCTION OF EPIDERMAL ORNITHINE DECARBOXYLASE FOLLOWING UV-B IRRADIATION IS INHIBITED BY ESTRIOL

The induction of epidermal ornithine decarboxylase (ODC) can be partia lly blocked by corticosteroids, retinoic acid or active vitamin D3. Th e influence of the other members of this so-called ''steroid hormone r eceptor superfamily'', namely the sex-steroids and thyroid hormone, is unknown in epidermis, but they enhance ODC induction in certain other tissues. Here we investigated whether topical estriol leads to a spon taneous and/or enhanced epidermal ODC induction 8 h after UV-B irradia tion of 6 postmenopausal women. Contrary to expectation, estriol did n ot stimulate induction but reduced induction by 44%. This observation raises the possibility that all members of the steroid hormone recepto r superfamily may share a common AP-1 binding site.