title: Modulation of monooxygenase activities by hematin and 7,8-benzoflavone in fetal tissues of rats, rabbits, and humans.
abstract: The rates of benzo[a]pyrene metabolism were stimulated markedly by micromolar quantities of hematin when assayed with either fetal or maternal extrahepatic tissue parparations (9,000 g supernatant fractions) from rats, rabbits and humans. Enzymatic induction was accompanied by either decreases in the magnitude of hematin stimulation or hematin-mediated inhibition of monooxygenase activities. Additions of 7,8-benzoflavone (BF) resulted in the inhibition of reaction rates in most experiments. With either fetal or maternal hepatic preparations from untreated rabbits, however, BF stimulated enzymatic activities; the greatest simulation occurred in fetal rabbit liver (10-fold). Nevertheless, inducer pretreatment was associated with inhibitory of BF on activities in hepatic homogenates.
mesh_terms: D000311:Adrenal Glands / Q000201:enzymology; D000818:Animals; D001571:Benzoflavones / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis; D004790:Enzyme Induction; D005260:Female; D005333:Fetus / Q000201:enzymology*; D005419:Flavonoids / Q000494:pharmacology*; D006418:Heme / Q000031:analogs & derivatives*; D006427:Hemin / Q000494:pharmacology*; D006801:Humans; D008099:Liver / Q000201:enzymology; D010105:Oxygenases / Q000096:biosynthesis / Q000378:metabolism*; D011247:Pregnancy; D011817:Rabbits; D051381:Rats
chemical_list: D001571:Benzoflavones; D005419:Flavonoids; D006418:Heme; D006427:Hemin; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases