In vivo induction of aryl hydrocarbon hydroxylase in human scalp hair follicles by topical application of a commercial coal tar preparation.

Five low-dose applications of a commercial coal tar preparation on a small scalp skin region resulted in an induction of aryl hydrocarbon hydroxylase (AHH) activity in freshly isolated human hair follicles. Large but reproducible interindividual differences in AHH-inducibility could be detected. The method offers the opportunity to measure AHH-inducibility, which has been correlated to the risk of developing chemical-induced cancer, in vivo in normal epithelium, a cell-type highly relevant for chemical carcinogenesis. Smoking habits did not have any effect on AHH-activity in freshly isolated hair follicles. Therefore the method potentially permits the identification of persons with high and low genetically determined AHH-inducibility.