 AO activity has been found to be much more active in higher primates (compared to rodents), though many factors may affect this activity, such as gender, age, cigarette smoking, drug usage, and disease states.Aldehyde oxidase is very concentrated in the liver, where it oxidizes multiple aldehydes and nitrogenous heterocyclic compounds, such as anti-cancer and immunosuppressive drugs.Some AO activity has been located in other parts of the body—including the lungs (epithelial cells and alveolar cells), the kidneys, and the gastrointestinal tract (small and large intestines).