The synthesis and purification of a component of fireMaster BP-6 and fireMaster FF-1, 2,3′,4,4′,5-pentabromobiphenyl, is described. The compound was found to be a potent inducer of liver microsomal drug-metabolizing enzymes in the rat, enhancing those enzymic activities induced by both phenobarbitone and 3-methylcholanthrene (i.e. cytochromes P-450 and P-448). The pentabromobiphenyl enhanced the activities of benzo[a]pyrene hydroxylase, dimethylamino-antipyrine N-demethylase and NADPH-cytochrome c reductase. The hepatic cytochromes b5 and P-450 were increased and the Soret peak maximum of the latter was shifted to 448.5 nm. The relative peak intensities and spectral shifts for the ethylisocyanide-binding difference spectra confirmed the mixed induction characteristics of 2,3′,4,4′,5-pentabromobiphenyl. 相似文献
A number of highly purified polychlorinated biphenyl (PCB) isomers and congeners were synthesized and administered to male Wistar rats at dosage levels of 30 and 150 μmol · kg−1. The effects of this in vivo treatment on the drug-metabolizing enzymes were determined by measuring the microsomal benzo[a]pyrene (B[a]P) hydroxylase, dimethylaminoantipyrine (DMAP) N-demethylase and NADPH-cytochrome c reductase enzyme activities, the cytochrome b5 content and the relative peak intensities and spectral shifts of the reduced microsomal cytochrome P-450: CO and ethylisocyanide (EIC) binding difference spectra. The results were compared to the effects of administering phenobarbitone (PB), 3-methylcholanthrene (MC) and PB plus MC (coadministered) to the test animals. The synthetic PCB congeners used in this study included 3,4,4′,5-tetrachlorobiphenyl (TCBP-1), 2,3′,4,4′-tetrachlorobiphenyl (TCBP-2), 2,3′,4,4′,5′-pentachlorobiphenyl (PCBP-1), 2,3,4,4′,5-pentachlorobiphenyl (PCBP-2), 2,3,3′,4,4′,5-hexachlorobiphenyl (HCBP-1), 2,3,3′,4′,5,6-hexachlorobiphenyl (HCBP-2), 2,3,3′,5,5′,6-hexachlorobiphenyl (HCBP-3), 2,2′,3,5,5′,6-hexachlorobiphenyl (HCBP-4) and 2,3,3′,4,5,5′-hexachlorobiphenyl (HCBP-5) and were used to reappraise the structure-activity rules for PCBs as hepatic microsomal enzyme inducers. The results suggested that (a) PCBs which induce MC or mixed-type activity must be substituted at both para positions, at least two meta positions but not necessarily on the same phenyl ring and can also contain one ortho chloro substituent; (b) due to the considerable structural diversity of the PB-type inducers the rules for induction of this activity by PCB congeners are not readily defined. 相似文献
Human placental microsomes were incubated with [3H]benzo[a]pyrene (BP) and Salmon sperm DNA and the resulting metabolite-nucleoside complexes resolved by Sephadex LH-20 chromatography. The metabolite pattern was analyzed by high-pressure liquid chromatography (HPLC). The incubates were also co-chromatographed with extracts obtained from incubates with rat liver microsomes and [14C]BP. Phenols, quinones and 7,8-dihydrodiol were detected in the placental incubates. Both 9,10- and 4,5-dihydrodiols were very low as compared with control rat liver samples. Placental microsomes catalyzed the binding of BP metabolites to DNA in vitro, giving rise to two main complexes which co-chromatographed with rat liver-produced peaks attributable to 7,8-diol-9,10-epoxide and 7,8-oxide and/or quinones when metabolized further. The nucleoside metabolite peaks attributable to 4,5-oxide and 9-phenol-4,5-oxide were lacking when compared with the binding pattern catalyzed by rat liver. Both the total binding and specific metabolite-nucleoside adducts in the placenta correlated with fluorometrically measured aryl hydrocarbon hydroxylase (AHH) activity and with the amount of dihydrodiol formed. The results demonstrate that both the metabolite pattern and the nucleoside-metabolite complexes formed by the placental microsomes in vitro differed greatly from those produced by rat liver microsomes. These studies also suggest that it is not possible to predict specific patterns of DNA binding from AHH measurements or even from BP metabolite patterns, especially when comparing different tissues and species. 相似文献
Human fibroblast cell lines were pulse-treated for 1 h with either methylnitrosourea (MNU) or ethylnitrosourea (ENU) at various time intervals before harvesting for chromosome analysis. Cells treated with 1 X 10(-3) M, 5 X 10(-4) M, and 1 X 10(-4) M final concentrations of MNU and ENU during the G2 or M phases of the cell cycle showed a significant increase in chromatid-type abnormalities over controls. Cells exposed to MNU or ENU 23 h before harvest showed some chromosome-type abnormalities, reflecting probable damage induced during the G1 phase of the cell cycle or derived from chromatid damage induced during the previous cell cycle. The mitotic indices and incidences of abnormalities suggested a dose response effect when cells were treated with the two higher concentrations and the three concentrations, respectively, of MNU or ENU. Chromatid abnormalities were observed in MUN and ENU-treated cells from each of four cell lines. From this investigation, it was concluded that MNU and ENU treatment of human diploid cell lines in vitro induced both chromatid and chromosome aberrations. MNU and ENU, both of which had previously been shown to be mutagenic in experimental animals, are, therefore, also considered to be mutagenic at the chromosome level in human fibroblasts grown and treated in cell culture. 相似文献
(1) The ATPase inhibitor protein has been isolated from rat liver mitochondria in purified form. The molecular weight determined by sodium dodecyl sulfate gel electrophoresis is approximately 9500, and the isoelectric point is 8.9.
(2) The protein inhibits both the soluble ATPase and the particle-bound ATPase from rat liver mitochondria. It also inhibits ATPase activities of soluble F1, and inhibitor-depleted submitochondrial particles derived from bovine heart mitochondria.
(3) On particle-bound ATPase the inhibitor has its maximal effect if incubated in the presence of Mg2+. ATP at slightly acidic pH.
(4) The inhibitor has a minimal effect on Pi-ATP exchange activity in sonicated submitochondrial particles. However, unexpectedly the inhibitor greatly stimulates Pi-ATP exchange activity in whole mitochondria while the low ATPase activity of the mitochondria is not affected. The possible mechanism of action of the inhibitor on intact mitochondria is offered. 相似文献
The binding of tritium-labelled 7,12-dimethylbenz[a]anthracene (DMBA), benzo[a]pyrene (BP) and 3-methylcholanthrene (MCA) to DNA or polynucleotides in vitro was re-examined both in the presence and in the absence of rat liver or human placental microsomes.A high level of non-enzymatic binding was evident when thymus DNA was used as acceptor. This non-enzymatic binding made it difficult to determine the effect of microsomes, except in the case of BP when induced rat microsomes were used. Better results were obtained using polynucleotides: a definite microsome-dependent binding occurred between all the polynucleotides and all the hydrocarbons tested.No clear evidence of binding catalysed by microsomes from human placenta was found except in polynucleotide-BP interactions: further studies are required to completely evaluate the ability of such nucleic acid-microsomal system for testing in vitro possible oncogenic substances in animals and humans. 相似文献
1. Using a plating technique, the mutagenic potentials of 2-acetamidofluorence (AAF) and N-hydroxy-AAF were examined after metabolic activation by liver preparations from different animals. Animals used were: male and female rats; male rats treated with 3-methylcholanthrene (MC); male rats treated with AAF; hamsters; guinea pigs; cotton rats and baboons. Irrespective of the animal susceptibility to AAF carcinogenesis, mutation frequency was always increased in the Salmonella typhimurium TA 1538 tester strain. Indeed, the greater response was found in the presence of liver from cotton rats, a species which is resistant to AAF-induced carcinogenesis.
2. Carcinogen binding, with labelled molecules, was also studied in liver cell constituents of rats, guinea pigs and cotton rats. A much better correlation was found between carcinogenicity and carcinogen binding, at least in those species studied, than between carcogenicity and plate test mutagenicity. The difficulty which this new information poses for the interpretation of plate tests is discussed.
The mutagenicity of dimethylnitrosamine (DMN) to mammalian cells was investigated using a metabolic activation system. Mutation from 8-azaguanine (8AG) sensitivity to resistance in FM3A cells, a cell line derived from C3H mouse mammary carcinoma, was found only in the presence of dimethylnitrosamine, mouse liver microsomes and cofactors. The different inducibility of the mutation was shown by the use of liver microsomes from different strains of mouse. 相似文献
The biotransformation of pregnenolone-7alpha-3H and of progesterone-7alpha-3H by porcine fetal and maternal adrenal homogenates at 56 and 112 days of pregnancy and of dehydroepiandrosterone-7alpha-3H by fetal adrenal homogenates has been investigated in vitro. Both pregnenolone-7alpha-3H and progesterone-7alpha-3H were metabolized extensively by maternal adrenal preparations, the principal radioactive metabolites isolated being cortisol, corticosterone, 11-deoxycortisol, deoxycorticosterone, 11beta-hydroxyprogesterone and androstenedione. In addition, 17alpha-hydroxyprogesterone, 20alpha-dihydroprogesterone and cortisone were formed from both substrates and 17alpha-hydroxypregnenolone and progesterone were formed from pregnenolone. Although essentially the same radioactive metabolites were isolated after incubation of fetal adrenal glands with pregnenolone-7alpha-3H or progesterone-7alpha-3H, a greater proportion of the radioactivity was associated with corticosteroids at 112 days of pregnancy than at 56 days. 11beta-Hydroxyandrostenedione and androstenedione were isolated and identified together with an unknown polar metabolite, after incubation of fetal adrenal tissue with dehydroepiandrosterone-7alpha-3H. These results are discussed in relation to feto-placental steroid biosynthesis and metabolism and the role of the fetal adrenal in the initiation of parturition in the pig. 相似文献