Interaction of certain metal ions with aryl hydrocarbon hydroxylase of rat lung microsomes

The effect of varying concentrations of cadmium, copper, zinc, and selenite on the activity of aryl hydrocarbon hydroxylase (AHH) of rat lungs was studied in vitro. All the metals resulted in a strong inhibition of enzyme activity. Copper and zinc were more inhibitory to rat lung AHH than cadmium and selenite. There was an additive inhibition of AHH activity when copper or zinc was added in the presence of cadmium. EDTA or glutathione exerted a protective effect on cadmium-induced inhibition of AHH activity. Prior incubation of the microsomes with N-ethylmaleimide, a thiol-blocking agent, had no effect on the inhibition of AHH activity caused by cadmium. Addition of cadmium along with zinc-thionein resulted in increased inhibition of rat lung AHH.