[Systemic localization of mixed function oxidases]

The localization of cytochrome P-450 dependent monooxygenase system in particular organs as well as in cellular structures has been presented. Attention was paid to microsomal, mitochondrial (inner membrane), nuclear (nuclear envelope), nucleolar localization of the system. In the liver cytochrome P-450 dependent monooxygenases occur in their maximum concentration, clustering in hepatocytes of the III acini zones. Cytochrome P-450 contents and the activity of its reductase gradually decrease in cells of the II and I zones. In the nephron the system under consideration also occurs in mitochondria and microsomes especially within the main nephron, that is, in the proximal convoluted tubules and in straight tubules. It has been estimated that the metabolic potential of the system does not exceed 15-20% of its hepatic potential. In the lungs which are an important pathway of xenobiotic penetration, cytochrome P-450 is found in Clara cells of the bronchioli, macrophages, II type alveolocytes and in the cells of endothelial blood vessels. In the alimentary tract the maximal concentration of the system in the proximal segment of the small intestine and its gradual reduction towards the rectum have been noted. In the villi and intestinal folds, enterocytes located on the peaks of the mentioned structures are characterized by the highest contents and activity of biotransformatic enzymes. The localization and role of the system in the placenta, elastic vessels, brain and prostatic gland have also been discussed.