Cytochrome P-450 localization in normal human adult and foetal liver by immunocytochemistry using a monoclonal antibody against human cytochrome P-450

Immunocytochemical studies with a monoclonal antibody (MAb-HL3), which recognises a major isozyme of human hepatic cytochrome P-450, have demonstrated this cytochrome in both cryostat and formalin-fixed paraffin-embedded sections of normal human adult liver. Prior trypsin digestion of the formalin-fixed sections prevented staining. There was a zonal distribution of immunoreactive cytochrome P-450, with localization predominantly in the hepatocytes of zone 3 of the hepatic acinus (the centrilobular region). Cytochrome P-450 was also demonstrated in foetal liver, but all foetal hepatocytes contained immunoreactive cytochrome P-450 and there was no zonal distribution of the protein. The biliary epithelium of adult liver contained a small amount of immunoreactive cytochrome P-450 whereas there was no immunoreactivity in the epithelium of foetal bile ducts.