The response of an organism to xenobiotic, often toxic, compounds is determined by various factors. One of the most important ones is the presence of enzymes metabolizing the xenobiotics; among them, the most prominent enzymes are cytochromes P450 (abbrev. CYP). The CYP enzymes metabolizing xenobiotics are present in the liver as well as in other parts of the gastrointestinal tract, in the lung, kidney, heart, nasal epithelium, leukocytes and other tissues. Their localization is expected to be connected with their yet unknown physiological function(s).

Keywords: Toxicology; cytochromes P450