title: [The effect of lysolecithin on rat liver microsome monooxygenase activity after induction by xenobiotics of the methylcholanthrene type].
abstract: Effects of exogenous gamma-myristoyl- and gamma-palmitoyllysolecithins on physico-chemical characteristics of rat liver microsomes, such as hydrophobicity and viscosity, as well as on oxidative NADPH-dependent O-deethylation of 7-ethoxycoumarin (7-EC), O-demethylation of p-nitroanisole (p-NA) and hydroxylation of 3.4-benz(a)pyrene (BP) induced by the mechylcholanthrene xenobiotics methylcholanthrene (MCh), beta-naphthoflavone (NF) and Sovol (SV) have been investigated. The specific inducible form of P-450c showed different affinity for the substrates. Lysolecithin decreased the hydrophobicity but only slightly increased membrane viscosity, whereas the monooxygenase substrates neutralized these effects. Lysolecithin (2-20 micrograms/mg of microsomal protein) inhibited the activity of deethylase 7-EC (maximally by 11%) in NF- and SV-induced microsomes, this inhibiting effect being more pronounced than that in MCh-induced microsomes. At higher concentrations lysolecithin inhibited the rate of 7-EC deethylation in MCh-induced microsomes more strongly; the maximal inhibition (23%) was observed at the protein concentration of 60 micrograms/mg. In case of NF- and SV-induced microsomes the inhibition was 18%. The inhibiting effect of lysolecithin on 7-EC dealkylation was expressed in a lesser degree than that on p-NA O-demethylation in induced (but not intact) microsomes. A significant positive correlation has been found between the changes in hydrophobicity and inhibition rates in the presence of lysolecithin, however only for 7-EC deethylation.
authors.forename: K N
authors.initials: KN
authors.lastname: Novikov
authors.forename: Z
authors.initials: Z
authors.lastname: Sumbalova
authors.forename: K N
authors.initials: KN
authors.lastname: Timofeev
mesh_terms: D000818:Animals; D000840:Anisoles / Q000378:metabolism; D001564:Benzo(a)pyrene / Q000378:metabolism; D001571:Benzoflavones / Q000494:pharmacology*; D003374:Coumarins / Q000378:metabolism; D004790:Enzyme Induction; D006900:Hydroxylation; D007425:Intracellular Membranes / Q000187:drug effects; D008244:Lysophosphatidylcholines / Q000494:pharmacology*; D008297:Male; D008745:Methylation; D008748:Methylcholanthrene / Q000494:pharmacology*; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000378:metabolism; D011078:Polychlorinated Biphenyls / Q000494:pharmacology*; D051381:Rats; D013379:Substrate Specificity; D019324:beta-Naphthoflavone
chemical_list: D000840:Anisoles; D001571:Benzoflavones; D003374:Coumarins; D008244:Lysophosphatidylcholines; C017299:7-ethoxycoumarin; D001564:Benzo(a)pyrene; C053040:Sovol; D008748:Methylcholanthrene; D019324:beta-Naphthoflavone; D011078:Polychlorinated Biphenyls; D006899:Mixed Function Oxygenases; C005306:4-nitroanisole
vernacular_title: Vliianie lizoletsitina na monoksigenaznye aktivnosti mikrosom pecheni krys posle induktsii ksenobiotikami metilkholantrenovogo tipa.