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Y Yamazoe

Publications and source records attributed to Y Yamazoe.

At least 181 records · Page 10Linked to original sources
PubMed1983

Metabolic activation of Trp-P-2, a tryptophan-pyrolysis mutagen, by isolated rat hepatocytes.

Metabolic activation of a tryptophan-pyrolysis product, 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), by isolated rat hepatocytes was studied. The substrate (Trp-P-2) disappearance by hepatocytes from untreated rats was slow, but enhanced by 3-methylcholanthrene (MC) pretreatment of rats. The covalent binding of Trp-P-2 to cellular macromolecules was detected in hepatocytes from untreated rats. The amount of covalent binding of Trp-P-2 to protein and RNA was greater than that to DNA. The covalent binding to Trp-P-2 to DNA, RNA and protein in hepatocytes from untreated rats was about 5-10 times less than that in hepatocytes from MC-pretreated rats. 7,8-Benzoflavone strongly inhibited the substrate disappearance and the binding of Trp-P-2 to DNA in hepatocytes from MC-pretreated rats. These results indicate that Trp-P-2 is metabolically activated by the P-448 type of cytochrome P-450 which is induced by MC. Diethylmaleate enhanced by about 50% the binding of Trp-P-2 to DNA in hepatocytes from MC-pretreated rats. On the other hand, cysteine inhibited the binding of Trp-P-2 to DNA with a concomitant reduction in the accumulation of the active metabolite, N-hydroxy-Trp-P-2 (N-OH-Trp-P-2). Sulfhydryl compounds seemed to play important roles in the detoxification of Trp-P-2.

Animals↗
PubMed1983

Sex difference of cytochrome P-450 in the rat: purification, characterization, and quantitation of constitutive forms of cytochrome P-450 from liver microsomes of male and female rats.

One of each constitutive form of cytochrome P-450 from liver microsomes of adult male and female rats was purified essentially following the same method to an apparent homogeneity as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The molecular weights estimated by the electrophoresis were 52,000 and 50,000 for forms of cytochrome P-450, P-450-male, and P-450-female, purified from male and female rats, respectively. In addition, the purified preparations of P-450-male and P-450-female showed properties different from each other with respect to spectral characteristics and catalytic activities. In Ouchterlony double diffusion plates, partially purified rabbit immunoglobulin G (IgG) raised against P-450-male and P-450-female showed very weak or no cross-reactivity with P-450-female and P-450-male, respectively. From these results, P-450-male was confirmed to be a form distinct from P-450-female. The anti-P-450-male and anti-P-450-female antibodies, which had been further purified by immunoadsorption, did not form any apparent precipitation bands with liver microsomes from untreated female and male rats, respectively. Supporting this, radial immunodiffusion analysis for P-450-male and P-450-female with an agarose gel impregnated with the rabbit antibodies showed that P-450-male and P-450-female appear in liver microsomes rather specifically depending on the sex hormones. Based on these results, sex differences in drug metabolism in the rat were confirmed as explicable, at least in part, by the presence of distinct forms of cytochrome P-450 in microsomes of male and female rats.

Animals↗
PubMed1983

Syntheses of hydroxyamino, nitroso and nitro derivatives of Trp-P-2 and Glu-P-1, amino acid pyrolysate mutagens, and their direct mutagenicities towards Salmonella typhimurium TA98 and TA98NR.

Hydroxyamino, nitroso and nitro derivatives of 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) and 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (Glu-P-1), mutagens-carcinogens produced on pyrolysis of amino acids, were synthesized from Trp-P-2 and Glu-P-1. 3-Hydroxyamino-1-methyl-5H-pyrido[4,3-b]indole (N-OH-Trp-P-2) and 2-hydroxyamino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (N-OH-Glu-P-1) were obtained with good yields by controlled catalytic reduction of 3-nitro-1-methyl-5H-pyrido[4,3-b]indole and 2-nitro-6-methyldipyrido[1,2-a:3',2'-d]imidazole. Subsequent oxidation of N-OH-Trp-P-2 and N-OH-Glu-P-1 with gamma-manganese dioxide yielded 3-nitroso-1-methyl-5H-pyrido[4,3-b]indole and 2-nitroso-6-methyldipyrido[1,2-a:3',2'-d]imidazole. All six synthesized compounds were mutagenic to Salmonella typhimurium TA98 without mammalian activation systems. The mutagenic activities of hydroxyamino and nitroso derivatives were identical for both S. typhimurium TA98 and TA98NR, the nitroreductase deficient strain. However, nitro derivatives were essentially mutagenic only towards S. typhimurium TA98.

Carbolines↗
PubMed1983

Activation and detoxication of N-hydroxy-Trp-P-2 by glutathione and glutathione transferases.

The roles of non-enzymatic and enzymatic glutathione (GSH) conjugation in the activation and detoxication of 3-hydroxy-amino-1-methyl-5H-pyrido[4,3-b]indole (N-OH-Trp-P-2) were studied in vitro. N-OH-Trp-P-2 is an active metabolite of 3-amino-1-methyl-5H-pyrido[4,3-d]indole (Trp-P-2), a mutagenic and carcinogenic heterocyclic amine. 3-Nitroso-1-methyl-5H-pyrido[4,3-b]indole (NO-Trp-P-2) reacted rapidly and non-enzymatically with GSH to form N-OH-Trp-P-2 and a small amount of two GSH conjugates (CN-1 and CN-2). On the other hand, non-enzymatic reaction of GSH with N-OH-Trp-P-2 was very slow, but the GSH conjugation with N-OH-Trp-P-2 was catalyzed by rat liver GSH transferase and a rat liver cytosol fraction to form three conjugates (CH-1, CH-2 and CH-3). The enzymatic conjugation was effectively inhibited by organic tin compounds which are known as powerful GSH transferase inhibitors. The conjugates were unstable enough to yield Trp-P-2 (from CN-1, CN-2 and CH-2) or N-OH-Trp-P-2 (from CH-3) on incubation at 37 degrees C for 30-60 min. Only CH-1 was stable under similar conditions. The mutagenicities of the GSH conjugates and the effects of GSH and GSH transferase were studied by using Salmonella typhimurium TA98 as the tester strain. The GSH conjugates except for CH-3 were completely detoxicated products, but CH-3 was found to be a more potent mutagen than N-OH-Trp-P-2. The mutagenicity of CH-3 seemed to be due to the direct action of the conjugate, and not to N-OH-Trp-P-2 formed from it.

Animals↗
PubMed1983

N-hydroxylation of carcinogenic and mutagenic aromatic amines.

N-Hydroxylation and mutagenic activation of heterocyclic aromatic amines from protein pyrolysis products were studied in rat liver microsomes and nuclei, rat hepatocytes and various species of purified cytochrome P-450. These mutagenic amines include Trp-P-2 (3-amino-1-methyl-5H-pyrido[4,3-b]indole), Trp-P-1 (3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole), Glu-P-1 (2-amino-6-methyldipyrido-[1,2-a:3',2'-d]imidazole), Glu-P-2 (2-amino-dipyrido[1,2-a:3',2'-d]imidazole) and IQ (2-amino-3-methyl-3H-imidazo-[4,5-f]quinoline). The number of revertants of Salmonella typhimurium TA 98 was always correlated to the amount of each of the N-hydroxylated metabolites in various experimental conditions. The N-hydroxylated amines covalently bound to DNA directly or after being acylated with amino acids by amino-acyl-tRNA synthetase. Various species of cytochrome P-450 preparations showed markedly different activity in N-hydroxylation and mutagenic activation of Trp-P-2, Glu-P-1 and IQ. A high spin form of cytochrome P-450, isolated from the liver of PCB-treated rats, showed very high activity in N-hydroxylation of Trp-P-2, Glu-P-1 and 2-aminofluorene, although its activity was very low in benzo(a)pyrene hydroxylation. The present results indicate that different species of cytochrome P-450 are involved in the N-hydroxylation and mutagenic activation of aromatic amines.

Amines↗
PubMed1983

A high-spin form of cytochrome P-450 highly purified from polychlorinated biphenyl-treated rats. Catalytic characterization and immunochemical quantitation in liver microsomes.

A high-spin form of cytochrome P-450 (termed PCB P-448-H) was purified from liver microsomes of polychlorinated biphenyl (PCB)-treated rats to homogeneity as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This high-spin form of cytochrome P-450 was distinguishable from a low-spin form of cytochrome P-450 (PCB P-448-L) purified from microsomes of PCB-treated rats by the criteria of molecular weights, peptide mapping, and immunochemical properties. In addition, PCB P-448-H catalyzed the hydroxylation of acetanilide (position 4) and biphenyl (positions 2 and 4), and N-hydroxylation of the promutagens 3-amino-1-methyl-5H-pyrido(4,3-b)indole (Trp-P-2), 2-amino-6-methyl-dipyrido(1,2-alpha:3',2'-d)imidazole (Glu-P-1), 2-aminofluorene, and 4-aminobiphenyl at much faster rates than did PCB P-448-L. These promutagens and aflatoxin B1 were efficiently metabolized to mutagens by this high-spin form of hemoprotein. Rabbit immunoglobulin G (IgG) raised against PCB P-448-H inhibited the microsomal O-depropylation activity of p-propoxyaniline. Radial immunodiffusion assay with the IgG showed that PCB P-448-H was one of the major forms of cytochrome P-450 in liver microsomes of PCB-treated rats. On the basis of these results, we propose that this high-spin form of cytochrome P-450 is a key enzyme activating a variety of environmental promutagens in the 9000 x g supernatant fraction of PCB-treated rats, which has been widely used as an activation system in routine mutation tests.

Animals↗
PubMed1983

Microsomal activation of 2-amino-3-methylimidazo[4,5-f]quinoline, a pyrolysate of sardine and beef extracts, to a mutagenic intermediate.

The mechanism involved in the metabolic activation of 2-amino-3-methylimidazo[4,5-f]quinoline, which is a pyrolysate isolated from broiled foods, to a mutagenic intermediate was studied in vitro. In a system containing hepatic microsomes and reduced nicotinamide adenine dinucleotide phosphate, 2-amino-3-methylimidazo[4,5-f]quinoline was converted to a product which was directly mutagenic to Salmonella typhimurium. The structure of the mutagenic metabolite was determined as the 2-N-hydroxy derivative on the basis of the chemical properties and the mass spectral evidence of the azoxy adduct with o-nitrosotoluene. The activation reaction was mediated by microsomal enzymes and was inhibited by carbon monoxide, 7,8-benzoflavone, and other chemicals which were known to inhibit the cytochrome P-450-dependent reaction. With the use of four forms of purified cytochrome P-450, the N-hydroxylation of 2-amino-3-methylimidazo[4,5-f]quinoline and the induction of the reverse mutation of the bacteria were clearly demonstrated to be catalyzed mainly by a high-spin form of cytochrome P-450, P-448 II-a.

Animals↗
PubMed1982

Evidence for the involvement of multiple forms of cytochrome P-450 in the occurrence of sex-related differences of drug metabolism in the rat.

Multiple forms of cytochrome P-450 in liver microsomes of untreated male and female rats could be divided into several fractions by the use of omega-amino-n-octyl Seph. 4B and DE-52 columns. Male cytochrome P-450 fractions (I-b - I-e) differed from female fractions (I-b - I-e) with respect to absorption peaks in carbon monoxide difference spectra and 7-propoxycoumarin O-depropylation activities. Although male and female I-a fractions showed quite similar protein bands on SDS-polyacrylamide gel electrophoresis, some protein bands in other male fractions (I-b - I-e) were absent in corresponding female fractions. Immunochemical examinations using immunoglobulin G raised to cytochrome P-450 purified from untreated male rats also showed that liver microsomes from male and female rats contain different forms of cytochrome P-450. Based on these results, we propose that sex-related differences of drug metabolizing activities in liver microsomes are caused by multiple forms of cytochrome P-450.

Animals↗
PubMed1982

Metabolic activation of 2-amino-9H-pyrido[2,3-b]indole by rat-liver microsomes.

Microsomal activation was required for the expression of the mutagenicity of 2-amino-9H-pyrido[2,3-b]indole (A alpha C) toward Salmonella typhimurium TA98. Pretreatment of rats with PCB, 3-methylcholanthrene or phenobarbital increased the mutagenic activating ability of hepatic microsomes by 16-, 10- and 2-fold, respectively, as compared with the untreated. The mutagenic activation of A alpha C by microsomes from PCB-treated rats was inhibited by ellipticine and alpha-naphthoflavone, whereas SKF 525-A and metyrapone showed a slight or no inhibitory effect, indicating that the P-448 form of cytochrome P-450 is involved in the mutagenic activation of A alpha C. Metabolic activation of A alpha C was studied by a high-performance liquid chromatography and Salmonella/microsome assay system, and the mutagenic metabolites formed were determined to be the N-hydroxy and nitroso derivatives, from the results of reaction with oxidizing or reducing agents. These results strongly indicate that N-hydroxylation of A alpha C by the P-448 type of cytochrome P-450 is essential for the mutagenic activation.

Animals↗
PubMed1982

Decrease in the activity of hepatic microsomal drug-metabolizing enzymes in tumor-bearing nude mice.

The activities of hepatic microsomal drug-metabolizing enzymes in nude mice (BALB/c-nu/nu) bearing tumors of human or nude mouse origin were studied. The content of cytochrome P-450 and the activities of cyclophosphamide oxidase, benzo[a]pyrene hydroxylase, aniline hydroxylase and benzphetamine N-demethylase were markedly decreased in tumor-bearing nude mice in accordance with previous observations in tumor-bearing rats and mice. These results indicate that decreases in the activities of hepatic microsomal drug-metabolizing enzymes are not the consequence of an immunoreactive process or cachexia.

Animals↗
PubMed1981

Metabolic activation of glutamic acid pyrolysis products, 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole and 2-amino-dipyrido[1,2-a:3',2'-d]imidazole, by purified cytochrome P-450.

Metabolic activation by cytochrome P-450 of glutamic acid pyrolysis products, 2-amino-6-methyldipyrido(1,2-a:3',2'-d)imidazole (Glu-P-1) and 2-amino-dipyrido(1,2,-a:3',2'-d)imidazole (Glu-P-2), to mutagenic metabolites was studied using Salmonella typhimurium TA98 as a tester strain. Cytochrome P-450, NADPH-cytochrome P-450 reductase and NADPH were essential requirements for the activation of these compounds. Of the four forms of cytochrome P-450 examined, polychlorinated biphenyls (PCB) P-448 and 3-methylcholanthrene (MC) P-448 purified from liver microsomes of rats treated with a PCB mixture and MC, respectively, showed high activity in the activation of both Glu-P-1 and Glu-P-2. The presence of three metabolites from Glu-P-1 or Glu-P-2 was demonstrated by high performance liquid chromatographic (HPLC) analysis. Among the metabolites of Glu-P-1, two metabolites were mutagenic without any further enzymatic activation. In accordance with the results of a mutation assay, PCB P-448 also exhibited higher activity to form the major mutagenic metabolite of Glu-P-1. The major active metabolite of Glu-P-1 was characterized as N-hydroxy-Glu-P-1 by chemical analysis using oxidizing and reducing reagents and by mass spectrometry.

Animals↗
PubMed1981

Metabolic activation of a tryptophan pyrolysis product, 3-amino-1-methyl-5H-pyrido[4,3-b]indole(TRP-P-2) by isolated rat liver nuclei.

The metabolic activation of a tryptophan pyrolysis product, 3-amino-1-methyl-5H-pyrido[4,3-b]indole(Trp-P-2), by rat liver nuclei was studied. Nuclei from the livers of rats treated with polychlorinated biphenyl (PCB) or 3-methylcholanthrene (MC) showed high mutagenic activity with Trp-P-2 in the Ames test, but activities with nuclei of untreated or phenobarbital (PB)-treated rat livers were quite low. The formation of N-hydroxy-Trp-P-2 by nuclei of PCB- or MC-treated rat livers was greater than that by nuclei of untreated or PB-treated rat livers. Similar results were observed with microsomes, which suggests that Trp-P-2 is metabolized by the same type of monoxygenase system in nuclei as in microsomes.

Animals↗