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1.
Phys Rev Lett ; 88(11): 117201, 2002 Mar 18.
Article in English | MEDLINE | ID: mdl-11909426

ABSTRACT

Experimental results for the susceptibility, magnetization, specific heat, 4f occupation number, Hall effect, and magnetoresistance for single crystals of the intermediate valence (IV) compound YbAl3 show that, in addition to the Kondo temperature scale T(K) approximately 670 K, there is a low temperature scale T(coh) approximately 30-40 K for the onset of Fermi liquid coherence. Furthermore, the crossover from the low temperature Fermi liquid regime to the high temperature local moment regime is slower than predicted by the Anderson impurity model. We suggest that these effects are generic for IV compounds and we discuss them in terms of the theory of the Anderson lattice.

2.
J Synchrotron Radiat ; 8(Pt 2): 191-5, 2001 Mar 01.
Article in English | MEDLINE | ID: mdl-11512723

ABSTRACT

Lanthanide and actinide intermetallic compounds display a wide range of correlated-electron behavior, including ferromagnetism, antiferromagnetism, nonmagnetic (Kondo) ground states, and so-called 'non-Fermi liquid' (NFL) behavior. The interaction between f electrons and the conduction band is a dominant factor in determining the ground state of a given system. However, lattice disorder can create a distribution of interactions, generating unusual physical properties. These properties may include NFL behavior in many materials. In addition, lattice disorder can cause deviations from standard Kondo behavior that is less severe than NFL behavior. A review of the lattice disorder mechanism within a tight-binding model is presented, along with measurements of the YbBCu4 and UPd(x)Cu(5-x) systems, demonstrating the applicability of the model. These measurements indicate that while the YbBCu4 system appears to be well ordered, both site interchange and continuous bond-length disorder occur in the UPd(x)Cu(5-x) series. Nevertheless, the measured bond-length disorder in UPdCu4 does not appear to be enough to explain the NFL properties simply with the Kondo disorder model.

3.
Phys Rev Lett ; 84(25): 5856-9, 2000 Jun 19.
Article in English | MEDLINE | ID: mdl-10991072

ABSTRACT

High-resolution atomic pair distribution functions have been obtained using neutron powder diffraction data from La2-xSrxCuO4 over the range of doping 0

4.
J Med Chem ; 43(19): 3487-94, 2000 Sep 21.
Article in English | MEDLINE | ID: mdl-11000003

ABSTRACT

A series of 3,6-diaryl-2,5-dihydroxybenzoquinones were synthesized and evaluated for their abilities to selectively activate human insulin receptor tyrosine kinase (IRTK). 2, 5-Dihydroxy-6-(1-methylindol-3-yl)-3-phenyl-1,4-benzoquinone (2h) was identified as a potent, highly selective, and orally active small-molecule insulin receptor activator. It activated IRTK with an EC(50) of 300 nM and did not induce the activation of closely related receptors (IGFIR, EGFR, and PDGFR) at concentrations up to 30 000 nM. Oral administration of the compound to hyperglycemic db/db mice (0.1-10 mg/kg/day) elicited substantial to nearly complete correction of hyperglycemia in a dose-dependent manner. In ob/ob mice, the compound (10 mg/kg) caused significant reduction in hyperinsulinemia. A structurally related compound 2c, inactive in IRTK assay, failed to affect blood glucose level in db/db mice at equivalent exposure levels. Results from additional studies with compound 2h, aimed at evaluating classical quinone-related phenomena, provided sufficient grounds for optimism to allow more extensive toxicologic evaluation.


Subject(s)
Benzoquinones/chemical synthesis , Hypoglycemic Agents/chemical synthesis , Receptor, Insulin/agonists , Administration, Oral , Animals , Benzoquinones/chemistry , Benzoquinones/pharmacokinetics , Benzoquinones/pharmacology , Cell Line , Dogs , Dose-Response Relationship, Drug , Drug Evaluation, Preclinical , ErbB Receptors/agonists , Glyburide/pharmacology , Humans , Hypoglycemic Agents/chemistry , Hypoglycemic Agents/pharmacokinetics , Hypoglycemic Agents/pharmacology , Insulin/blood , Insulin/pharmacology , Macaca mulatta , Male , Mice , Rats , Receptors, Platelet-Derived Growth Factor/agonists , Receptors, Somatomedin/agonists , Structure-Activity Relationship
5.
J Pharmacol Exp Ther ; 291(3): 1068-74, 1999 Dec.
Article in English | MEDLINE | ID: mdl-10565826

ABSTRACT

The cytochrome P-450 (CYP)3A4-mediated metabolism of diclofenac is stimulated in vitro by quinidine. A similar effect is observed in incubations with monkey liver microsomes. We describe an in vivo interaction of diclofenac and quinidine that leads to enhanced clearance of diclofenac in monkeys. After a dose of diclofenac via portal vein infusion at 0.055 mg/kg/h, steady-state systemic plasma drug concentrations in three male rhesus monkeys were 87, 104, and 32 ng/ml, respectively (control). When diclofenac was coadministered with quinidine (0.25 mg/kg/h) via the same route, the corresponding plasma diclofenac concentrations were 50, 59, and 18 ng/ml, representing 57, 56, and 56% of control values, respectively. In contrast, steady-state systemic diclofenac concentrations in the same three monkeys were elevated 1.4 to 2.5 times when the monkeys were pretreated with L-754,394 (10 mg/kg i.v.), an inhibitor of CYP3A. Further investigation indicated that the plasma protein binding (>99%) and blood/plasma ratio (0.7) of diclofenac remained unchanged in the presence of quinidine. Therefore, the decreases in plasma concentrations of diclofenac after a combined dose of diclofenac and quinidine are taken to reflect increased hepatic clearance of the drug, presumably resulting from the stimulation of CYP3A-catalyzed oxidative metabolism. Consistent with this proposed mechanism, a 2-fold increase in the formation of 5-hydroxydiclofenac derivatives was observed in monkey hepatocyte suspensions containing diclofenac and quinidine. Stimulation of diclofenac metabolism by quinidine was diminished when monkey liver microsomes were pretreated with antibodies against CYP3A. Subsequent kinetic studies indicated that the K(m) value for the CYP-mediated conversion of diclofenac to its 5-hydroxy derivatives was little changed (75 versus 59 microM), whereas V(max) increased 2.5-fold in the presence of quinidine. These data suggest that the catalytic capacity of monkey hepatic CYP3A toward diclofenac metabolism is enhanced by quinidine.


Subject(s)
Anti-Inflammatory Agents, Non-Steroidal/pharmacokinetics , Antimalarials/pharmacology , Aryl Hydrocarbon Hydroxylases , Diclofenac/pharmacokinetics , Quinidine/pharmacology , Animals , Biotransformation , Blood Proteins/metabolism , Chromatography, Liquid , Cytochrome P-450 CYP3A , Cytochrome P-450 Enzyme System/metabolism , Drug Interactions , Liver/drug effects , Liver/enzymology , Liver/metabolism , Macaca mulatta , Male , Mass Spectrometry , Microsomes, Liver/drug effects , Microsomes, Liver/metabolism , Oxidoreductases, N-Demethylating/metabolism
6.
Rapid Commun Mass Spectrom ; 13(19): 1943-50, 1999.
Article in English | MEDLINE | ID: mdl-10487941

ABSTRACT

During the early phase of a drug discovery process, in order to facilitate the selection of drug candidates from a discovery research program, a liquid chromatography tandem mass spectrometry (LC/MS/MS) strategy has been developed to assess the preliminary pharmacokinetics and metabolism of new drug entities. For pharmacokinetic studies using multiple reaction monitoring (MRM), the parent drug concentration and its 'suspected' (predictable) metabolites were monitored in the biological samples simultaneously. For metabolic identification, the general methodologies most frequently used to search for metabolites include full scan, precursor-ion scan, product-ion scan and neutral-loss scan. However, when the metabolites do not produce intense signals for tandem mass spectrometry, a more sensitive and selective assay has to be developed, and MRM would be the method of choice. Likewise, an intelligent guess as to which MRM transitions ought to be used for the metabolites will be considered, based on the product ion mass spectrum of the parent drug.


Subject(s)
Chromatography, Liquid/methods , Drugs, Investigational/pharmacokinetics , Mass Spectrometry/methods , Acetonitriles , Animals , Biotransformation , Drugs, Investigational/metabolism , Glucuronides/metabolism , Haplorhini , Humans , Liver/metabolism , Methylation , Rats
7.
Drug Metab Dispos ; 27(5): 581-7, 1999 May.
Article in English | MEDLINE | ID: mdl-10220486

ABSTRACT

The pharmacokinetics and hepatic metabolism of [3H] ivermectin (IVM) and [3H]cyclosporin A (CSA) were investigated in a subpopulation of the CF-1 mouse stock naturally deficient in mdr1a p-glycoprotein (PGP). A survey of key drug-metabolizing activities in liver fractions from PGP-deficient (-/-) or wild-type (+/+) animals indicated the two subpopulations are not different in hepatic metabolic activity and capacity. Intravenous pharmacokinetics of CSA were identical between the two groups, and results from microsomal incubations indicated similar biotransformation of IVM and CSA in liver. Intestinal excretion of [3H]IVM and [3H]CSA was enhanced in PGP (+/+) animals. Absence of PGP resulted in higher blood concentrations of IVM after oral dosing, suggesting enhanced absorption of IVM in (-/-) mice. Concentrations of [3H]IVM and [3H]CSA were always greater in the brains of (-/-) mice compared with (+/+) mice after either i.v. or oral administration. In contrast, liver concentrations of either compound were not different between (+/+) and (-/-) animals after an i.v. dose. These results show the PGP (-/-) and (+/+) subpopulations of CF-1 mice are useful for studying the role of mdr1a PGP in systemic exposure and tissue disposition of PGP substrates in the absence of metabolism differences.


Subject(s)
ATP Binding Cassette Transporter, Subfamily B/deficiency , Cyclosporine/pharmacokinetics , Ivermectin/pharmacokinetics , ATP Binding Cassette Transporter, Subfamily B/genetics , Animals , Bile/metabolism , Biotransformation , Brain/metabolism , Cyclosporine/blood , Intestinal Mucosa/metabolism , Ivermectin/blood , Liver/metabolism , Male , Mice , Mice, Knockout , Tissue Distribution
8.
Drug Metab Dispos ; 27(3): 365-72, 1999 Mar.
Article in English | MEDLINE | ID: mdl-10064567

ABSTRACT

The nonsteroidal anti-inflammatory drug diclofenac causes a rare but potentially fatal hepatotoxicity that may be associated with the formation of reactive metabolites. In this study, three glutathione (GSH) adducts, namely 5-hydroxy-4-(glutathion-S-yl)diclofenac (M1), 4'-hydroxy-3'-(glutathion-S-yl)diclofenac (M2), and 5-hydroxy-6-(glutathion-S-yl)diclofenac (M3), were identified by liquid chromatography-tandem mass spectrometry analysis of bile from Sprague-Dawley rats injected i.p. with a single dose of diclofenac (200 mg/kg). These adducts presumably were formed via hepatic cytochrome P-450 (CYP)-catalyzed oxidation of diclofenac to reactive benzoquinone imines that were trapped by GSH conjugation. In support of this hypothesis, M1, M2, and M3 were generated from diclofenac in incubations with rat liver microsomes in the presence of NADPH and GSH. Increases in adduct formation were observed when incubations were performed with liver microsomes from phenobarbital- or dexamethasone-treated rats. Adduct formation was inhibited by polyclonal antibodies against CYP2B, CYP2C, and CYP3A (40-50% inhibition at 5 mg of IgG/nmol of CYP) but not by an antibody against CYP1A. Maximal inhibition was obtained when the three inhibitory antibodies were used in a cocktail fashion (70-80% inhibition at 2.5 mg of each IgG/nmol of CYP). These data suggest that diclofenac undergoes biotransformation to reactive metabolites in rats and that CYP isoforms of the 2B, 2C, and 3A subfamilies are involved in this bioactivation process. With respect to CYP2C isoforms, rat hepatic CYP2C7 and CYP2C11 were implicated as mediators of the bioactivation based on immunoinhibition studies using antibodies specific to CYP2C7 and CYP2C11. Screening for GSH adducts also was carried out in human hepatocyte cultures containing diclofenac, and M1, M2, and M3 again were detected. It is possible, therefore, that reactive benzoquinone imines may be formed in vivo in humans and contribute to diclofenac-mediated hepatic injury.


Subject(s)
Anti-Inflammatory Agents, Non-Steroidal/pharmacokinetics , Cytochrome P-450 Enzyme System/metabolism , Diclofenac/pharmacokinetics , Glutathione/metabolism , Microsomes, Liver/metabolism , Animals , Bile/metabolism , Biotransformation , Cells, Cultured , Chromatography, Liquid , Female , Humans , Male , Mass Spectrometry , Microsomes, Liver/enzymology , Rats , Rats, Sprague-Dawley
10.
Drug Metab Dispos ; 24(10): 1111-20, 1996 Oct.
Article in English | MEDLINE | ID: mdl-8894513

ABSTRACT

Indinavir, a potent and specific inhibitor of human immunodeficiency virus protease, is undergoing clinical investigation for the treatment of acquired immunodeficiency syndrome. The studies described herein were designed to characterize the absorption, distribution, metabolism, and excretion of the drug in rats, dogs, and monkeys. Indinavir exhibited marked species differences in elimination kinetics. The plasma clearance was in the rank order: rat (107 ml/min/kg) > monkey (36 ml/min/kg) > dog (16 ml/min/kg). Significant differences in the bioavailability of indinavir also were observed. When given orally as a solution in 0.05 M citric acid, the bioavailability varied significantly from 72% in the dog to 19% in the monkey, and 24% in the rat. These differences in bioavailability were attributed mainly to species differences in the magnitude of hepatic first-pass metabolism. The distribution of indinavir was studied only in rats, both intravenously and orally. Intravenously, indinavir was distributed widely throughout the body. Brain uptake studies showed that indinavir penetrated the blood-brain barrier, but that the penetration was limited. After oral administration, indinavir was distributed rapidly into and out of the lymphatic system. The rapid lymph transfer is of clinical relevance, because a primary clinical hallmark of acquired immunodeficiency syndrome is the depletion of CD4 lymphocytes. Biliary and urinary recovery studies revealed that metabolism was the major route of indinavir elimination in all species, and N-dealkylation, N-oxidation, and hydroxylation seemed to be the major pathways. Although limited to qualitative aspects, the metabolite profile obtained from in vitro microsomal studies generally reflected the in vivo oxidative metabolism of indinavir in all species studies. Results from the chemical and immunochemical inhibition studies indicated the possible involvement of isoforms of the CYP3A subfamily in the oxidative metabolism of indinavir in rats, dogs, and monkeys. This is consistent with our previous studies, which have shown that CYP3A4 is the isoform responsible for the oxidative metabolism of indinavir in human liver microsomes. Furthermore, the in vivo oxidative metabolism of indinavir in rats, dogs, and monkeys was qualitatively similar to that in humans. The high degree of similarity in the metabolite profiles of drug metabolism between animals and humans validates the use of these animal models for toxicity studies of indinavir. Attempts were made to quantitatively extrapolate in vitro metabolic data to in vivo metabolism. With the application of the well-stirred and parallel-tube models, the hepatic clearance and hepatic extraction ratio were calculated using the in vitro Vmax/Km values. In rats, the predicted hepatic clearance (31 ml/ min/kg) and hepatic extraction ratio (0.47) agreed well with the observed in vivo hepatic clearance (43 ml/min/kg) and hepatic extraction ratio (0.68). In addition, the hepatic clearance of indinavir was predicted reasonably well in dogs and monkeys. Based on the in vitro intrinsic clearance of human liver microsomes, a small but significant hepatic first-pass metabolism (ca. 25%) is expected in humans.


Subject(s)
HIV Protease Inhibitors/pharmacokinetics , Indinavir/pharmacokinetics , Animals , Area Under Curve , Dogs , HIV Protease Inhibitors/metabolism , Haplorhini , Indinavir/metabolism , Male , Microsomes, Liver/metabolism , Rats , Rats, Sprague-Dawley , Species Specificity
12.
Pharm Res ; 12(6): 884-8, 1995 Jun.
Article in English | MEDLINE | ID: mdl-7667195

ABSTRACT

PURPOSE: To evaluate regional intestinal absorption and the feasibility of sustained release dosage form development for an HIV protease inhibitor, L-735,524, METHODS: L-735,524 free base or sulfate salt was administered orally as suspension, solution or in solid dosage forms to fasted or fed Beagle dogs. Delayed-release dosage forms with "slow" or "fast" in vitro dissolution rates were evaluated in vivo to assess plasma concentration profiles. In addition, drug was administered directly into the jejunum or colon of animals, and drug concentrations determined in portal circulation to characterize absorption from these sites. RESULTS: L-735,524 sulfate was well absorbed orally form a solution or capsule formulation if fasted animals' stomachs were preacidified with citric acid solution. A free base suspension, delivered in divided doses to fed animals, was also well absorbed. Prototype extended release dosage forms of L-735,524 produced a reduction in peak plasma levels but failed to prolong absorption and extend plasma concentrations compared to an immediate release capsule. Administration of L-735,524 sulfate solution (pH < 3) as bolus solution or by infusion into the jejunum resulted in rapid but incomplete absorption compared to oral gavage. The free base suspension (pH 6.5) delivered into jejunal or colonic regions did not produce measurable systemic plasma concentrations. CONCLUSIONS: Extended release formulations did not prolong absorption of L-735,524 in dogs. Optimal L-735,524 absorption was dependent on solubility in an acidic environment in the duodenum.


Subject(s)
HIV Protease Inhibitors/pharmacokinetics , Intestinal Absorption , Intestinal Mucosa/metabolism , Pyridines/pharmacokinetics , Administration, Oral , Animals , Dogs , HIV , Hydrogen-Ion Concentration , Indinavir , Models, Biological , Time Factors
13.
Carcinogenesis ; 13(4): 519-23, 1992 Apr.
Article in English | MEDLINE | ID: mdl-1576702

ABSTRACT

It is well known that food restriction diminishes tumor formation, but mechanisms responsible are difficult to define because multiple physiological changes result from dietary alterations. Studies in this report were designed to focus specifically on the effects of food restriction on hepatic metabolism of polycyclic aromatic hydrocarbons following liver transplantation. By placing livers from food-restricted and untreated rats into naive controls, the effects of diet could be restricted to the liver. After a 15 min infusion of [3H]benzo[a]pyrene under these conditions, food restriction increased polar metabolites in liver (70 pmol/g) and blood (8 pmol/ml) compared to controls approximately 2-fold. Four hours after liver transplantation, levels of polar metabolites in blood were diminished by approximately 50% but were still approximately 2-fold higher in the food-restricted than in the control group. Lung, kidney, spleen, adrenal, ovary, colon, heart and brain also contained higher levels of polar metabolites in the food-restricted than in the control group. The more hydrophobic glucuronides and sulfate conjugates accounted for most of the elevation in polar metabolites in blood from the food-restricted group. In spite of the increase in circulating metabolites in blood of food-restricted animals, DNA binding in liver, lung and kidney was identical in tissues from control and food-restricted groups. In order to evaluate the hypothesis that food restriction stimulated the release of hepatic benzo[a]pyrene metabolites, a liver perfusion model was employed. Maximal rates of release of polar metabolites into the effluent perfusate were approximately 30 and approximately 45 nmol/g/h in livers of control and food-restricted rats respectively. Moreover, rates of metabolism of the model compound p-nitroanisole and glucuronidation of p-nitrophenol were also approximately 2-fold higher in livers from food-restricted than control rats. However, rates of monooxygenation were the same in microsomes prepared from livers of food-restricted or control animals. These results support the hypothesis that food restriction enhances the supply of cofactors which stimulate metabolism of polycyclic aromatic hydrocarbons. This detoxification process may be an important mechanism involved in the protective action of reduced food intake.


Subject(s)
Carcinogens/metabolism , Diet, Reducing , Polycyclic Compounds/metabolism , Animals , Benzo(a)pyrene/metabolism , Female , Glucuronates/metabolism , Inactivation, Metabolic , Rats , Rats, Inbred Strains
14.
Cancer Res ; 52(6): 1639-42, 1992 Mar 15.
Article in English | MEDLINE | ID: mdl-1540972

ABSTRACT

Benzo(a)pyrene 7,8-dihydrodiol-9,10-epoxide (BPDE), accepted as the ultimate carcinogen of benzo(a)pyrene, has a very short half-life in aqueous solutions yet induces lung tumors when injected into infant mice. To evaluate the possibility that metabolites of BPDE, principally in the form of stable conjugates, contribute to binding to DNA in peripheral tissues, infant mice were injected i.p. with 39 nmol (+/- ) anti-BPDE. One h after injection, 5% of the dose was recovered in serum and appeared mostly as conjugated metabolites (54% as glucuronides and 16% as glutathione conjugates). Amounts of direct acting electrophiles in serum estimated by trapping with DNA comprised less than 0.02% of the injected dose. No more than 10% of the radioactivity in extracts of liver, lung, and kidney was recovered as BPDE. Glutathione conjugates predominated in the liver and lung, whereas glucuronides were the major metabolites in kidney. Radioactivity bound to DNA in liver, lung, and kidney was 21.5, 42.7, and 7.8 pmol/mg, respectively. Despite the rapid conversion of BPDE to stable conjugates, 32P-postlabeling profiles of DNA adducts in lung closely resembled that noted after addition of BPDE directly to lung homogenate. Thus, the reactive intermediate as well as stable conjugates of BPDE may be transported to target tissues where they initiate tumors.


Subject(s)
7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide/metabolism , Polydeoxyribonucleotides/metabolism , 7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide/pharmacokinetics , Animals , Animals, Newborn , Mice , Polydeoxyribonucleotides/pharmacokinetics
15.
Environ Mol Mutagen ; 19(3): 253-8, 1992.
Article in English | MEDLINE | ID: mdl-1572348

ABSTRACT

Comparison of the mutagenicity of nine isomeric benzo(a)pyrenyl [B(a)P] phenols conjugated with either sulfate or glucuronide was carried out using strain Salmonella typhimurium TA98. Of the nine conjugates tested, only B(a)P-1-sulfate was mutagenic. Accordingly, the mutagenicity of B(a)P-1-sulfate was compared with that of B(a)P and 1-hydroxybenzo(a)pyrene [B(a)P-1-OH] in the presence and absence of rat lung S9 and Aroclor-induced liver S9 with and without an NADPH-generating system. B(a)P-1-sulfate was slightly mutagenic, whereas B(a)P and the 1-hydroxy derivative were nonmutagenic when S9 fractions and NADPH were omitted. Addition of induced liver S9 with NADPH caused mutagenicity with B(a) -1-OH greater than B(a)P greater than B(a)P-1-sulfate. B(a)P-1-sulfate was the only mutagenic species when lung S9 was added. This mutagenicity did not require NADPH. Sodium sulfite, an inhibitor of arylsulfatase, decreased the mutagenicity of B(a)P-1-sulfate. These data suggest that a unique mutagenic species is generated from B(a)P-1-sulfate via arylsulfatase in rat lung.


Subject(s)
Benzopyrenes/toxicity , Mutagens/toxicity , Animals , Arylsulfatases/antagonists & inhibitors , Benzopyrenes/metabolism , Biotransformation , Glucuronates/toxicity , Liver/enzymology , Lung/enzymology , Male , Mutagenicity Tests , NADP/physiology , Rats , Rats, Inbred Strains , Salmonella typhimurium/drug effects , Sulfates/toxicity , Sulfites/pharmacology
16.
Carcinogenesis ; 12(11): 2073-9, 1991 Nov.
Article in English | MEDLINE | ID: mdl-1934292

ABSTRACT

Diet has been implicated as a major determinant of chemical carcinogenesis. Accordingly, rates of benzo[a]pyrene (B[a]P) metabolism were compared in hepatocytes isolated from rats maintained on control, high-fat or food-restricted AIN-76A diets. Rats maintained on the food-restricted diet were given 65% of food consumed by the control group fed ad libitum. The high-fat diet group had free access to a modified AIN-76A diet in which the amount of corn oil was increased 4-fold at the expense of digestible carbohydrates. The triacylglycerol content in hepatocytes varied in direct proportion to dietary fat and calories and was 66 +/- 5, 105 +/- 7 and 192 +/- 16 nmol/mg dry wt in cells isolated from rats fed food-restricted, control and high-fat diets respectively. In contrast, the rate of B[a]P metabolism was highest in hepatocytes from rats maintained on the food-restricted diet and lowest in cells from animals given the high-fat diet (i.e. food-restricted greater than control greater than high-fat). Thus, an inverse correlation existed between the rate of B[a]P metabolism and the content of triacylglycerols in hepatocytes. At a cell density of approximately 2 mg dry wt/ml, rates of B[a]P (40 microM) metabolism were 1324 +/- 186, 1150 +/- 198 and 829 +/- 76 pmol/mg dry wt/h, respectively, in hepatocytes isolated from rats fed food-restricted, control and high-fat diets. When cells were incubated with a lower concentration of B[a]P (10 microM), the rate of B[a]P metabolism was greater than 2-fold higher in hepatocytes from rats fed the food-restricted diet compared to the rate measured in cells from the high-fat group. Glucuronidation of B[a]P metabolites in hepatocytes from rats fed high-fat diet was also approximately 30% lower than rates determined for control and food-restricted groups. These diet-induced alterations in rates of B[a]P metabolism occurred in the absence of changes in specific activity of arylhydrocarbon hydroxylase or UDP-glucuronosyltransferase in liver microsomes. Further, the rate of 7-ethoxycoumarin metabolism, a more hydrophilic substrate, was not affected by diet and B[a]P but not 7-ethoxycoumarin accumulated in hepatic lipid droplets. Thus, diet-induced changes in intracellular triacylglycerol, particularly in lipid droplets, may alter access of B[a]P to binding sites on arylhydrocarbon hydroxylase and thereby modulate B[a]P metabolism in intact hepatocytes.


Subject(s)
Benzo(a)pyrene/metabolism , Diet, Reducing , Dietary Fats/adverse effects , Liver/metabolism , Triglycerides/physiology , Analysis of Variance , Animals , Centrifugation, Density Gradient , Coumarins/metabolism , Gene Expression Regulation , Liposomes/chemistry , Male , Rats , Rats, Inbred Strains
17.
Carcinogenesis ; 12(5): 783-6, 1991 May.
Article in English | MEDLINE | ID: mdl-2029742

ABSTRACT

The important problem of whether metabolites and DNA adducts from benzo[a]pyrene (B[a]P) originate in the liver or target tissues was assessed using orthotopic liver transplantation. Following liver transplantation, the only source of metabolites for release into the blood and accumulation in target tissues is the liver. [3H]B[a]P (4 microM, 5 Ci/mmol) was infused into the portal vein of rats, and livers were perfused and either transplanted to a second rat or sham-operated and left in situ (non-transplant group). After 4 h, seven organs were collected and polar metabolites and DNA adducts were measured. In both groups, B[a]P in blood samples was below the limits of detection while levels of B[a]P in liver samples were approximately 5 pmol/g and polar metabolites were approximately 10 pmol/g. Concentrations of polar metabolites were also nearly identical in peripheral tissues from both groups. Phenols, glucuronides, sulfates and an unidentified metabolite of B[a]P were also similar, but GSH conjugate(s) had a tendency to be lower in blood of animals with transplanted livers. DNA adducts ranged from minimal values near levels of detection to approximately 0.2 pmol/mg DNA in lung, liver, and kidney. Importantly, there were no differences in DNA binding between the transplant and non-transplant groups. Taken together, these data provide compelling evidence that the liver is the predominant site of conversion of B[a]P into polar metabolites which are transported to target tissues and subsequently bind to DNA. Release of polar metabolites from the liver may represent a novel pathway for delivery of carcinogen conjugates to target tissues.


Subject(s)
Carcinogens , Liver/drug effects , Polycyclic Compounds/toxicity , Animals , Benzo(a)pyrene/pharmacokinetics , Benzo(a)pyrene/toxicity , Female , Liver Transplantation , Postoperative Period , Rats , Rats, Inbred Strains , Tissue Distribution
18.
J Nutr ; 121(1): 131-7, 1991 Jan.
Article in English | MEDLINE | ID: mdl-1899448

ABSTRACT

The influence of high fat or food-restricted diets on key enzymes associated with polycyclic aromatic hydrocarbon metabolism was assessed in liver, lung, kidney and stomach of rats. Animals had access ad libitum to the AIN-76A purified diet (control) or were given 65% of the intake of controls for 3 wk. The high fat diet was isoenergetic to the control diet by substituting corn oil for equal energy from carbohydrate and addition of cellulose to obtain equal energy density. Activities of arylhydrocarbon hydroxylase and 7-ethoxycoumarin O-deethylase were significantly increased in lungs of food-restricted rats and decreased by the high fat diet but were not altered in liver. Both diets increased arylhydrocarbon hydroxylase approximately twofold in kidney. Glucose 6-phosphate and 6-phosphogluconate dehydrogenase were lowered in lung, kidney and liver by the high fat diet. Hepatic glutathione S-transferase was increased by high fat feeding. Food restriction decreased activities of arylsulfatase and beta-glucuronidase about 40% in lung. Hepatic arylsulfatase was also decreased about 40% by this treatment. Changes in hydrolase activities in livers and lungs of animals maintained on restricted diets raises in the interesting possibility that net production of glucuronide and sulfate conjugates of carcinogens by the liver and their hydrolysis in lung is altered by food restriction.


Subject(s)
Carcinogens/metabolism , Dietary Fats/administration & dosage , Food Deprivation , Liver/enzymology , Polycyclic Compounds/metabolism , 7-Alkoxycoumarin O-Dealkylase/metabolism , Animals , Aryl Hydrocarbon Hydroxylases/metabolism , Arylsulfatases/metabolism , Dietary Fats/pharmacology , Glucosephosphate Dehydrogenase/metabolism , Glucuronidase/metabolism , Glucuronosyltransferase/metabolism , Glutathione Transferase/metabolism , Kidney/enzymology , Lung/enzymology , Male , Phosphogluconate Dehydrogenase/metabolism , Rats , Rats, Inbred Strains , Stomach/enzymology
19.
Food Chem Toxicol ; 28(7): 491-5, 1990 Jul.
Article in English | MEDLINE | ID: mdl-2210521

ABSTRACT

To investigate the influence of unsaturation of dietary fat on the oxidation of benzo[a]pyrene-7,8-dihydrodiol to DNA binding products, we fed diets containing 10% by weight of either safflower oil or lard to weanling rats. Compared with the group fed lard, the group fed safflower oil had 2.0- to 2.5-fold higher levels of unstimulated and peroxidation-stimulated activation of benzo[a]pyrene-7,8-dihydrodiol to DNA-binding metabolites, respectively, in hepatic nuclei. The rats fed safflower oil had a significant 75% higher level of lipid peroxidation as measured by the thiobarbituric acid assay. Rats fed safflower oil also showed 30% greater binding of (-)-benzo[a]pyrene-7,8-dihydrodiol oxidation products to DNA compared with animals fed lard, following administration of this dihydrodiol enantiomer through the hepatic portal vein. Significant diet-dependent differences were not apparent in DNA binding of the (+)-isomer, or in the tetrol production from either isomer; however, rats fed safflower oil showed a trend towards production of higher levels of anti-benzo[a]pyrene diol epoxide-derived tetrols. Activities of hepatic nuclear and microsomal aryl hydrocarbon hydroxylase and of cytosolic and microsomal glutathione S-transferases were not significantly affected by diet, nor was the activity of microsome-mediated binding of (+)- or (-)-benzo[a]pyrene-7,8-dihydrodiol to DNA in vitro. The results indicate that polyunsaturated fat in quantities as low as 10% by weight of the diet is sufficient to increase significantly the extent to which DNA-binding metabolites of benzo[a]pyrene are produced, and that this increased metabolism is likely to be independent of mixed-function oxidases.


Subject(s)
DNA/metabolism , Dietary Fats, Unsaturated/pharmacology , Dihydroxydihydrobenzopyrenes/metabolism , Lipid Peroxidation , Animals , Dietary Fats/pharmacology , Eating/drug effects , Liver/drug effects , Liver/metabolism , Male , Organ Size/drug effects , Oxidation-Reduction , Rats , Rats, Inbred Strains , Safflower Oil/pharmacology , Weight Gain/drug effects
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