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Biomedical subjects

H Wallin

Publications and source records attributed to H Wallin.

At least 37 records · Page 2Linked to original sources
PubMed1996

Oxidative stress associated with exercise, psychological stress and life-style factors.

Oxidative stress is a cellular or physiological condition of elevated concentrations of reactive oxygen species that cause molecular damage to vital structures and functions. Several factors influence the susceptibility to oxidative stress by affecting the antioxidant status or free oxygen radical generation. Here, we review the effect of alcohol, air pollution, cigarette smoke, diet, exercise, non-ionizing radiation (UV and microwaves) and psychological stress on the development of oxidative stress. Regular exercise and carbohydrate-rich diets seem to increase the resistance against oxidative stress. Air pollution, alcohol, cigarette smoke, non-ionizing radiation and psychological stress seem to increase oxidative stress. Alcohol in lower doses may act as an antioxidant on low density lipoproteins and thereby have an anti-atherosclerotic property.

Air Pollution↗
PubMed1995

Lung carcinoma and malignant mesothelioma in patients exposed to Thorotrast: incidence, histology and p53 status.

In a previous registry-based survey of 999 patients injected with alpha-emitting 232ThO2 (Thorotrast), we identified elevated risks for lung carcinoma and malignant mesothelioma. Since injected Thorotrast is retained lifelong mostly in liver, spleen and lymph nodes, the mesothelial surfaces of these organs are constantly irradiated. Thorotrast-administered patients also perpetually exhale 220Rn, a 232Th-daughter. Study of Thorotrast-exposed patients may, therefore, provide data with regard to carcinogenicity of radon exposure, a current public health concern, as well as the pathogenesis of malignant mesothelioma. The incidence and histologic types of lung carcinoma and malignant mesothelioma within the cohort were examined by review of available histopathologic material and medical records. Further, mutations of the p53 gene were analyzed whenever possible as it has previously been suggested that radon-associated lung carcinomas exhibit specific mutational patterns. The cumulative risk for lung carcinoma reached 11.0% based on 20 confirmed cases. Nine were small cell lung cancer (SCLC), whereas the expected frequency was 18%. The risk for malignant mesothelioma reached 2.5% based on 7 cases. The actuarial risk of malignant mesothelioma for patients given more than 20 ml Thorotrast was 7.8% compared to 1.4% for patients administered smaller amounts. Seven lung carcinomas and 5 malignant mesotheliomas were analyzed for p53 mutations; only 1 (in a lung adenocarcinoma) was detected. A possible association between Thorotrast and SCLC is suggested. In addition, a possible dose-response gradient exists for Thorotrast and malignant mesothelioma.

Adolescent↗
PubMed1995

Inhibition of intercellular communication by condensates of high and low tar cigarettes.

Inhibition of gap junctional intercellular communication (GJIC) is a predictive short term test for tumor promoting activity. A new metabolic cooperation assay has been developed, which takes the cytochrome P-450 metabolism into account. In this assay the inhibitory activity of tobacco smoke condensates (CSC) and CSC fractions from high and low tar cigarettes was tested. CSC of both high and low tar cigarettes and fractions thereof contained tumor promoting activity. The tar yield of the cigarettes did not closely reflect the effects in the GJIC assay and the major constituent nicotine had no effect. The effect was only marginally greater in cells expressing different cytochrome P-450 enzymes, indicating that the active substances are not metabolized by these enzymes. The activities of CSC fractions were considerably lower than the activities in the unfractionated CSC. This may indicate that compounds in the CSC act strongly synergistically. Furthermore, CSC and CSC fractions synergistically inhibit GJIC with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate, indicating different mechanisms of action.

Cell Communication↗
PubMed1994

New serum markers for small-cell lung cancer. I. The ganglioside fucosyl-GM1.

The ganglioside fucosyl-GM1 (FucGM1) has been suggested as a marker for small-cell lung cancer (SCLC). Immunohistochemical analyses have shown the expression of the ganglioside in tumors in 75 to 90% of patients with SCLC. We have demonstrated that the ganglioside is shedded from SCLC cells both in vitro and in vivo, and that the antigen can be detected in sera from SCLC patients by an immunochemical analysis. The FucGM1 antigen has recently been shown to act as a target for antibody-dependent cellular cytotoxicity. This may provide a rationale for developing immunotherapy against SCLC. We used an immunoassay based on the scintillation proximity assay to analyze the concentrations of FucGM1 in sera from 112 SCLC patients, 21 patients with non-SCLC, 4 patients with other cancer forms, and 20 healthy controls. Sera were collected at the time of diagnosis before initiation of chemotherapy. The expression of FucGM1 was related to age, sex, blood group of the patient, and to the stage of disease and organ site involvement of metastases. The sera of 50% of the patients with SCLC were positive for FucGM1, and 12 of 21 sera from non-SCLC patients were markedly elevated. In SCLC sera, the concentration of FucGM1 in positive sera ranged from 7 to more than 3000 ng/ml FucGM1. None of 20 controls were positive. FucGM1 correlated to organ site involvement of metastases (p = 0.0016). The ganglioside was detected both at significantly higher concentrations (p = 0.0005) and in significantly more patients (p = 0.0026) with metastases to both the liver and bone marrow, compared to patients with metastases to the liver only.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomarkers, Tumor↗
PubMed1993

Induction of CD3 delta epsilon omega by phorbol 12-myristate 13-acetate.

The effect of phorbol 12-myristate 13-acetate (PMA) on the synthesis, assembly and processing of the components of the T cell receptor (TcR) was studied with special focus on the CD3 omega chain. Treatment of the human leukemic T cell line Jurkat with PMA increased the synthesis of the Ti alpha, CD3 gamma and CG3 zeta chains two- to threefold and the synthesis of Ti beta and CD3 delta epsilon omega complexes five- to sevenfold as assessed by metabolic labeling, immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by scanning densitometry. The amount of total assembled TcR complexes increased approximately threefold and the maturation of the TcR was not affected as determined by analysis of oligosaccharide side chain processing in the Golgi apparatus. Activation of Jurkat cells with anti-CD3 monoclonal antibody, calcium ionophore, or mitogenic lectins did not affect the synthesis of the TcR components. In other cells studied (the human leukemic T cell line CEM, a panel of variants of the Jurkat T cell line and peripheral blood mononuclear cells) PMA also increased the synthesis of the TcR components. However, for all cell lines studied the amount of TcR complexes expressed on the cell surface was decreased after 16 h of PMA treatment. Based on these results we propose a role of CD3 omega in retention of TcR complexes. From PMA-treated CEM cells more than 50-fold the amount of CD3 delta epsilon omega complexes was immunoprecipitated as compared to the amount obtained from untreated Jurkat cells, and these observations indicate that the CEM cell line may be a qualified candidate for purification of CD3 omega.

Ammonium Chloride↗
PubMed1993

Cytochrome P450-mediated metabolism of tumour promoters modifies the inhibition of intercellular communication: a modified assay for tumour promotion.

The role of metabolism of tumour promoters on the inhibition of intercellular communication was investigated in a modified V79 metabolic cooperation system. V79 cells, which stably express different rat cytochrome P450 enzymes (CYP1A1, CYP1A2 or CYP2B1), were used in the metabolic cooperation assay. The inhibitory effect on intercellular communication of four compounds was changed in cells expressing cytochrome P450 enzymes, compared to cells without. The phorbol ester TPA and di(2-ethylhexyl)phthalate blocked intercellular communication in all the cell lines tested, but expression of CYP1A1 enzyme reduced the inhibitory activity in these cells. Diethylstilbestrol caused inhibition only with cells containing cytochrome P450 enzymes. In contrast, the benzene metabolite hydroquinone inhibited metabolic cooperation preferentially in cells without cytochrome P450 enzymes. The inhibition of metabolic cooperation by another benzene metabolite, phenol, was not affected by the cytochrome P450 enzymes. The inhibitory activity of several chemicals that have not been tested previously was analysed in the new metabolic cooperation assay. The inhibitory activity of none of these chemicals was affected by cytochrome P450-associated metabolism. 7-Octylindolactam V was as potent as TPA, whereas the related indolactam V was 100-fold less active. The carcinogenic aromatic amine 4-aminobiphenyl, but not its primary metabolite 4-hydroxyaminobiphenyl, inhibited metabolic cooperation. Other known carcinogens, ochratoxin A, aflatoxin B1 and 4-nitrobiphenyl, did not inhibit metabolic cooperation in either V79 cells expressing or cells not expressing cytochrome P450. We conclude that cytochrome P450-associated metabolism plays an important role in the inhibition of gap junctional intercellular communication of some tumour promoters. The modified metabolic cooperation assay presented here is valuable for detecting some inhibitory chemicals which have been 'false negative' in previous assays for gap junctional intercellular communication. The assay also discloses that cytochrome P450 metabolism alters intercellular communication by a mechanism other than metabolism of the exogenous inhibitor.

Animals↗
PubMed1993

Bioactivation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]-pyridine by liver microsomes from three different rat strains.

The biotransformation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]-pyridine (PhIP) and the protein binding of PhIP and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) was studied using microsomes from PCB-pretreated or untreated male rats of the strains, Wistar, Fischer and Sprague-Dawley. The microsomal monooxygenases, P450IA1 and IA2, which are important for the biotransformation of heterocyclic amines, were quantified by immunoblots. The two metabolites detected, 2-amino-1-methyl-6-(4'-hydroxyphenyl)imidazo[4,5-b]pyridine (4'OH-PhIP) and 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine (N2-OH-PhIP) were formed in similar amounts whereas no minor metabolites were found in our highly sensitive radiochemical assay. Irrespective of the rat strain used, pretreatment with PCB significantly induced both the activation and the detoxication in all three rat strains. Except for a significantly higher concentration of P450IA2 in microsomes from control and PCB induced Wistar rats, no major differences between the strains were found.

Animals↗
PubMed1992

Serum immunoassay of a small cell lung cancer associated ganglioside: development of a sensitive scintillation proximity assay.

We here report an enzyme linked immunosorbent assay (ELISA) and a scintillation proximity assay (SPA) for detection of the ganglioside FucGM1 in sera from small cell lung cancer (SCLC) patients. The SPA was more sensitive and reproducible than the ELISA. In this assay, monoclonal antibodies specific for FucGM1 were bound to SPA particles and incubated with labelled FucGM1 and 100 microliters test-serum overnight, and counted in a beta-counter. The sensitivity was 0.2 ng. Seven out of twenty sera from SCLC patients were positive, whereas none of twenty sera from healthy individuals were positive for FucGM1. The SPA was more sensitive than the previously reported HPTLC as well as a direct ELISA.

Carbohydrate Sequence↗
PubMed1992

Effect of dietary fiber on the disposition and excretion of a food carcinogen (2-14C-labeled MeIQx) in rats.

We studied to what extent dietary fiber may affect uptake, retention, and excretion of a food carcinogen (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, MeIQx) occurring in fried meat. Four diets--one fiber-free control and three containing either insoluble dietary fiber isolated from sorghum (100 g/kg) and wheat bran (100 g/kg) or the highly soluble pectin (50 g/kg)--were investigated. The fiber diets were given in amounts of 10 g/day to rats. Thus, each rat received 1 or 0.5 g fiber and 100 micrograms 2-14C-labeled MeIQx uniformly mixed in its daily diet. A 4-day adaptation period with unlabeled MeIQx was followed by a 5-day experimental period with 14C-labeled MeIQx, during which urine and feces were collected separately for analysis of radioactivity and mutagenicity. Furthermore the composition and the fermentability of the dietary fiber were determined. The present study shows that a diet containing fiber, especially fiber isolated from sorghum and wheat bran, affects the excretion pattern of the food carcinogen MeIQx in a manner suggesting a lower uptake and a decreased transit time through the gastrointestinal tract in a more diluted form than a nonfiber diet. Furthermore, less radioactivity was retained in the kidneys with sorghum and wheat bran than with the other two diets. On the other hand, none of these types of dietary fiber affected the retention of the hepatocarcinogen MeIQx in the liver 24 hours after the last oral intake. DNA adducts were formed to a higher extent in the kidney than in the liver. The highest levels were found in animals given the wheat bran diet.

Animals↗
PubMed1992

Covalent binding of food carcinogens MeIQx, MeIQ and IQ to DNA and protein in microsomal incubations and isolated rat hepatocytes.

The metabolic activation of 14C-labelled food carcinogens 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) to macromolecular bound species was studied in microsomal and hepatocellular incubations. Several data indicated that the covalent binding was dependent on P450 enzymes: It was dependent on NADPH, it was induced many times by the P450 IA1 and IA2 upregulators beta-naphthoflavone and polychlorinated biphenyls, and was inhibited by the P450 IA1 and IA2 inhibitor alpha-naphthoflavone. In both hepatocellular and microsomal incubations the three compounds bound with similar efficiency, with IQ being somewhat more potent compared to MeIQx and MeIQ. The binding appeared to follow saturation kinetics with Km values less than 20 microM. In incubations with hepatocytes the compounds bound to both cellular DNA and to bovine serum albumin in the medium. The fact that 13-26% of total adducts were formed with bovine serum albumin, indicates that reactive metabolites of the compounds may be transported and react at distant sites from their formation without any further activation.

Animals↗
PubMed1991

Formation of a glutathione conjugate and a semistable transportable glucuronide conjugate of N2-oxidized species of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in rat liver.

We have previously shown that 2-hydroxamino-1-methyl-6-phenylimidazo[4,5-b]pyridine(2-h ydroxamino-PhIP) is the principal metabolite leading to mutations in Salmonella typhimurium TA98 and DNA damage in mammalian cells. In rat hepatocytes this metabolite can be further conjugated to 2-(N-beta-D-glucuronopyranosyl (hydroxamino)-1-methyl-6-phenylimidazo[4, 5-b]pyridine[N(OH)-gluc-PhIP]. Its rate of formation was increased in hepatocytes from polychlorinated biphenyl (PCB)-pretreated animals. This metabolite is the main metabolite of PhIP in bile and it is hydrolyzed both by human and rat intestinal bacteria. Smaller amounts are excreted into urine. The evidence for the proposed structure is based on 1H- and 13C-NMR, beta-glucuronidase-lability giving 2-hydroxamino-PhIP upon hydrolysis and on the results obtained by using biochemical enzyme inhibitors. N(OH)-gluc-PhIP may be important for genotoxic lesions and tumors of 2-amino-1methyl-6-phenylimidazo [4,5-b]pyridine (PhIP) in extrahepatic tissue. In hepatocytes and bile from PCB-pretreated rats a PhIP-glutathione conjugate, 2-glutathionyl-1-methyl-6-phenylimidazo[4,5-b]pyridine (GSH-PhIP) was also found. The evidence for the proposed structure is based on 1H-NMR and high-resolution mass spectrometry. The metabolite can also be produced by a direct nucleophilic substitution of the nitro group in 2-nitro-PhIP by glutathione (GSH) in vitro. The metabolite did not form from 2-hydroxamino-PhIP and GSH either directly or in the presence of glutathione S-transferase. The formation of GSH-PhIP in rat liver and isolated cells only at a high rate of 2-hydroxamino-PhIP formation (PCB-treated animals) indicates that 2-nitro-PhIP may be formed in the liver during such N-oxidation of PhIP.

Animals↗
PubMed1991

The effect of dose and enzyme inducers on the metabolism of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in rats.

Male Fischer 344 rats were given a single dose of 0.03-30 mg/kg of [2-14C]2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine ([14C]PhIP), the radioactivity in urine and feces was determined over 48 h, and the major metabolites were identified and quantified. Dose had little effect on the profile of metabolites in the urine but did influence the profile in the feces. PhIP was more efficiently metabolized at higher doses. In addition, rats were pretreated with Aroclor 1254 (PCB), 3-methylcholanthrene (MC), phenobarbital (PB), PhIP and corn oil prior to a single dose of [14C]PhIP, and compared with a control group receiving [14C]PhIP only. The major metabolites in the urine and feces were quantitated for each group, as well as PhIP binding to serum proteins, hemoglobin and selected tissues. Pretreatment with MC and PCB resulted in an increase in the amount of 4'-hydroxylation of PhIP and a decrease in the amount of N-hydroxylated metabolites in the urine. Pretreatment with PB resulted in an increase in the amount of N-hydroxylated metabolites, but a decrease in 4'-hydroxylation. Pretreatment with either MC or PCB resulted in an increase in PhIP binding to the liver and kidney, while reducing the binding in other tissues. Animals pretreated with PhIP showed few significant differences from the untreated group, while pretreatment with PB in general resulted in a decrease of PhIP binding in tissues.

Animals↗
PubMed1991

Immunochemical detection of rodent hepatic and urinary metabolites of cooking-induced food mutagens.

Monoclonal antibodies, previously selected to bind either 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) or 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) were evaluated to determine their binding properties with several known metabolites of these compounds purified from rat hepatocyte cultures. Both 2-N- and 5-substituted MeIQx metabolites were recognized by antibodies AIA-2 and AIA-11, while antibodies AIA-1 and AIA-12 bound N-substituted metabolites only. Anti-PhIP antibodies bound N-hydroxy-PhIP, N-sulfinamide-glutathione-PhIP and N-hydroxy-glucuronide-PhIP. Immunoaffinity columns incorporating these antibodies were used to concentrate and purify both the unmetabolized parent compounds and several relatively non-polar metabolites from the urine of rats exposed either to MeIQx or PhIP. Several of these metabolites corresponded with available standards of previously identified polar conjugate metabolites, e.g. N-sulfamate-MeIQx and N(OH)-gluc-PhIP, while others are as yet unidentified. Immunoaffinity chromatography is demonstrated as a promising means of selectively concentrating metabolites of PhIP and MeIQx from urine.

Animals↗
PubMed1991

Reductive metabolism and protein binding of chromium(VI) by P450 protein enzymes.

The cytochrome P450-dependent reduction of Cr(VI) using reconstituted phospholipid vesicles containing purified preparation of various forms of rabbit and rat liver microsomal cytochrome P450 has been investigated. The alcohol-induced form of the rat, P450IIE1, was the most efficient enzyme, 7.2 +/- 0.40 nmol Cr/nmol P450/min, whereas the corresponding rates for rat P450IA1, rat IIB1, rabbit IIB4, rabbit IA2 and rabbit IIE1 were 1.7 +/- 0.09, 2.5 +/- 0.08, 1.6 +/- 0.08, 2.5 +/- 0.15 and 1.6 +/- 0.08 nmol Cr/nmol P450/min respectively. NADPH-cytochrome P450 reductase had Cr(VI) reductase activity which was dependent on enzyme concentration. Below 0.15 nmol P450 reductase/ml the sp. act. was low and constant, while at a higher concentration the activity was markedly dependent upon the amount of enzyme present. In a quantitative binding assay it was shown that binding of [51Cr]Cr(VI) to the catalytic enzymes was proportional to the enzyme concentration up to 0.8 nmol P450/ml, which caused binding of 70% of the total radioactivity. Analysis by SDS-PAGE and autoradiography exhibited binding to the individual catalytic proteins of [51Cr]Cr. EDTA treatment removed the radioactivity from the bands matching P450 and P450 reductase, indicating that Cr(III) is bound to the proteins. The reducing activity of both P450 and P450 reductase was potently inhibited by oxygen. The inhibitory effect of oxygen is not due to reoxidation of the reduced Cr and redox cycling. Rat P450IA1 ethoxycoumarin O deethylase activity was inhibited after preincubation with chromate (CrO4(2-). The P450 reductase inhibitor 2'-AMP stimulated the anaerobic P450 reductase dependent Cr(VI) reductase rate approximately 2-fold. Both CO and CCl4 inhibited the different P450 enzymes to various extents. With rabbit P450IIE1 CCl4 stimulated the Cr(VI) reduction approximately 4-fold, whereas the activity of the other enzymes was inhibited when the reconstituted system was incubated with CrO4(2-) and CCl4 prior to NADPH addition. Neither CO nor CCl4 affected the Cr(VI) reducing activity of the P450 reductase. The difference in CrO4(2-) reducing activity of the P450 enzymes and binding to the enzymes may be important for in vivo endoplasmic catalytic metabolism of CrO4(2-).

7-Alkoxycoumarin O-Dealkylase↗
PubMed1990

Activation of microsomal glutathione transferase activity by reactive intermediates formed during the metabolism of phenol.

The activity of microsomal glutathione transferase was increased 1.7-fold in rat liver microsomes which carried out NADPH dependent metabolism of phenol. Known phenol metabolites were therefore tested for their ability to activate the microsomal glutathione transferase. The phenol metabolites benzoquinone and 1,2,4-benzenetriol both activated the glutathione transferase in microsomes 2-fold independently of added NADPH. However, NADPH was required to activate the enzyme in the presence of hydroquinone. Catechol did not activate the enzyme in microsomes. The purified enzyme was activated 6-fold and 8-fold by 5 mM benzenetriol and benzoquinone respectively. Phenol, catechol or hydroquinone had no effect on the purified enzyme. When microsomal proteins that had metabolized [14C]phenol were examined by SDS polyacrylamide gel electrophoresis and fluorography it was found that metabolites had bound covalently to a protein which comigrated with the microsomal glutathione transferase enzyme. We therefore suggest that reactive metabolites of phenol activate the enzyme by covalent modification. It is discussed whether the binding and activation has general implications in the regulation of microsomal glutathione transferase and, since some reactive metabolites might be substrates for the enzyme, their elimination through conjugation.

Animals↗
PubMed1990

Differential rates of metabolic activation and detoxication of the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine by different cytochrome P450 enzymes.

Rat liver microsomes metabolized the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) to the genotoxic metabolite 2-hydroxamino-1-methyl-6-phenylimidazo[4,5-b]pyridine (2-hydroxamino-PhIP) and to the detoxified product 2-amino-4'-hydroxy-1-methyl-6-phenylimidazo[4,5-b]pyridine (4'-hydroxy-PhIP). A 25-fold higher rate of metabolism was measured in microsomes from polychlorinated-biphenyl-treated rats (94 nmol/mg proteins/30 min) in comparison with those from untreated rats. Other effective inducers of PhIP metabolism were beta-naphthoflavone and isosafrole (ISF), whereas phenobarbital was ineffective. About twice as much 2-hydroxamino-PhIP as 4'-hydroxy-PhIP was formed in microsomes irrespective of the inducer the rats had been treated with. The metabolism was dependent on NADPH and was abolished by the cytochrome P450 inhibitor alpha-naphthoflavone. In a reconstituted enzyme system purified rat cytochrome P450 IA2 (P450ISF-G) had the highest N-hydroxylation rate (30 nmol/nmol P450/30 min) closely followed by the rat cytochrome P450 IA1 (P450BNF-B). Less activity was seen with rat P450 IIC11 (P450UT-A) and rabbit P450 IA2 (P450 LM4). Rat P450 IIE1 (P450j), P450 IIB1 (P450PB-B) and rabbit P450 IIB4 (P450 LM-2) and P450 IIE1 (P450 LM3a) were essentially inactive. Rat P450 IA1 (P450BNF-B) produced five times more 4'-hydroxy-PhIP (32 +/- 2 nmol/nmol P450/30 min) than did P450 IA2 (P450ISF-G). Hence, the measured ratio of activation to detoxication for rat P450 IA2 (P450ISF-G) enzyme was 7-fold higher than that of the other active P450 enzymes.

Animals↗
PubMed1989

Characterisation of metabolites of the food mutagens 2-amino-3-methylimidazo[4,5-f]quinoline and 2-amino-3,4-dimethylimidazo[4,5-f]quinoline formed after incubation with isolated rat liver cells.

The metabolism of 14C-labelled 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) was studied in suspensions of hepatocytes isolated from PCB-pretreated rats. The metabolites found after incubation of IQ/MeIQ (0.1 mM) with PCB-pretreated hepatocytes for 3 h were separated into three principal groups: ethyl acetate-extractable metabolites (2-4%), water soluble metabolites (94-98%) and covalently bound metabolites (0.4-0.5%). The water soluble metabolites were separated by HPLC. The metabolites were evaluated by beta-glucuronidase lability, sulphate incorporation and compared with glucuronides formed by microsomes. Mass spectroscopy and proton NMR were also run. The major metabolites formed were a N2-sulphamate, an O-sulphate in position 5 for IQ and 5 for MeIQ and an O-glucuronide in the same position. The MeIQ N2-sulphamate was much less abundant than the IQ N2-sulphamate. When compared with hepatocytes from uninduced rats, it was found that primarily the formation of ring-hydroxylated conjugates increased after PCB-pretreatment. The major ethyl acetate-extractable metabolites were the N2-acetyl derivatives and an unidentified metabolite. A small peak representing the 5-hydroxy-IQ or 5-hydroxy-MeIQ could also be seen in the HPLC chromatogram of the ethyl acetate extractable metabolites. All major water soluble products described in hepatocytes were also found in urine and bile of uninduced rats exposed to IQ/MeIQ in vivo.

Animals↗