The induction of epidermal ornithine decarboxylase following UV-B irradiation is inhibited by estriol

The induction of epidermal ornithine decarboxylase (ODC) can be partially blocked by corticosteroids, retinoic acid or active vitamin D 3 . The influence of the other members of this so-called «steroid hormone receptor 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 spontaneous and/or enhanced epidermal ODC induction 8 h after UV-B irradiation of 6 postmenopausal women. Contrary to expectation, estriol did not stimulate induction but reduced induction by 44%. This observation raises the possibility that all members of the steroid hormone receptor superfamily may share a common AP-1 binding site