Decreased induction of aryl hydrocarbon hydroxylase activity in hyperproliferative hairless mouse epidermis.

Hairless mice were treated topically with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to induce experimental chloracne. The aryl hydrocarbon hydroxylase (AHH) activity in the epidermis was monitored. TCDD is a potent inducer of AHH activity in normal skin. However, as continued TCDD application induced hyperproliferative and hyperkeratotic changes in the epidermis, the AHH activity decreased. Similar suppression in AHH activity was demonstrated in epidermis made hyperplastic by (a) tape stripping of stratum corneum and (b) repeated application of 50% oleic acid. This suggests that the epidermal AHH response varies with the state of epidermal differentiation. In the hairless mouse, AHH activity in hyperplastic epidermis is lower than that in normal epidermis.