Human skin aryl hydrocarbon hydroxylase.

Aryl hydrocarbon hydroxylase (AHH) activity has been measured in full-thickness biopsies of human skin from patients with and without psoriasis. Basal levels of enzyme activity varied over a fivefold range and were not related to age, sex or clinical condition. Induction of AHH activity by the application of coal tar resulted in a two- to fivefold increase in activity above basal levels, which was not related to the presence or absence of psoriasis. Separation of human skin into dermis and epidermis showed that human skin AHH activity is predominantly dermal.