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 D3. 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.