A method for assaying aryl hydrocarbon hydroxylase in man using fibroblasts cultured in vitro from oral mucosa

Animal studies have linked aryl hydrocarbon hydroxylase (AHH) with cancer induction by polycyclic aromatic hydrocarbons (PAH), but the relationship between the activation of PAH by AHH and cancer induction in man is unclear. Studies using human lymphocytes to investigate this relationship have produced conflicting results. This report describes a technique for assaying AHH in fibroblasts isolated and cultured from normal human oral mucosa. Fibroblasts were cultured from normal portions of routine oral mucosal biopsy specimens obtained from 6 patients, and AHH activity was found in fibroblasts cultured from all the specimens. AHH activity was induced by 1,2-benzanthracene and reached a peak after 48 h. The assay had a pH optimum of 8.6 and an absolute requirement for reduced nicotinamide-adenine dinucleotide phosphate. The fibroblasts maintained their inducibility of AHH through 11 cell passages. Fibroblasts cultured from oral mucosal biopsy specimens offer several advantages over other systems for comparison of individual differences in AHH activity in man, including the consistent presence of inducible AHH activity, stability of enzyme activity in culture, provision of ample number of cells for study, and availability of oral mucosal specimens from patients having routine diagnostic biopsies.