Exposure of Physalaemus cuvieri (Anura) to benzo[a]pyrene and α-naphthoflavone: Morphofunctional effects on hepatic melanomacrophages and erythrocytes abnormalities

Benzo[a]pyrene (BaP) is a high-risk contaminant of elevated toxicity. Its biotransformation process occurs as the expression of CYP1A1 increases and produces toxic metabolites. In turn, α-naphthoflavone (aNF) represents an inhibitor of CYP1A1, preventing BaP metabolism. Toxicological studies in anurans show alterations in the melanomacrophage (MM) detoxification cell after exposure to xenobiotics. In this study, the production of melanin by MMs was evaluated, as were morphological alterations in the cytoskeleton, phagocytosis and the genotoxicity effects after exposure of an anuran species to BaP and aNF. Physalaemus cuvieri received subcutaneous injections of 2 mg/kg and/or 20 mg/kg aNF. For phagocytosis analyses, animals received an intraperitoneal injection with 0.4% trypan blue. The results revealed that melanin synthesis increased by 503.2% in animals exposed to BaP after 48 h, which was related to the antioxidant action of melanin, whereas the decreased in synthesis of 25.6% with the BaP + aNF interaction resulted in high toxicity to MMs and cell degeneration. The phagocytic activity reduced to 37.6% in animals exposed to BaP, characterizing a functional impairment; however, the BaP + aNF interaction led to the restoration of phagocytosis, reaching 419.23%. The decreased rate or absence of abnormalities may be explained by the fact that only the less damaged erythrocytes remained in the bloodstream, whereas the most damaged cells died. In conclusion, BaP and aNF are toxic to P. cuvieri, bringing risks to herpetofauna.

2,3,7,8-Tetrachlorodibenzo-p-dioxin induces alterations in myogenic differentiation of C2C12 cells

Dioxin-induced toxicities that affect the development of the motor system have been proposed since many years. However, cellular evidence and the molecular basis for the effects are limited. In this study, a cultured mouse myoblast cell line, C2C12, was utilized to examine the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on myogenic differentiation and expression of acetylcholinesterase (AChE), a neuromuscular transmission-related gene. The results showed that TCDD exposure at 10^-10 M repressed the myotube formation of C2C12 cells by disturbing the fusion process and suppressing the expression of myosin heavy chain, a myobute structural protein, and not by induction of cytotoxicity. Furthermore, TCDD dose dependently suppressed the transcriptional expression and enzymatic activity of AChE during the myogenic differentiation, particularly in the middle stage. However, the administration of aryl hydrocarbon receptor antagonists, CH223191 and alpha-naphthoflavone, did not completely reverse the TCDD-induced downregulation of muscular AChE during myogenic differentiation. These findings suggest that low dose exposure to dioxin may result in disturbances of muscle differentiation and neuromuscular transmission.

Stage-dependent ethoxyresorufin-O-deethylase (EROD) in vivo activity in medaka (Oryzias latipes) embryos

Using medaka (Oryzias latipes) embryos, this study aimed to quantitatively characterize the stage-dependent in vivo ethoxyresorufin-O-deethylase (EROD) as indicator of cytochrome P4501A (CYP1A) activity. Embryos were challenged for 24-h to an agonist (β-naphthoflavone [BNF], 2.5, 5, 10, and 20 μg L(-1)) or to its combination (2.5 μg L(-1)) with an antagonist (α-naphthoflavone [ANF], 25, 50, 100, and 200 μg L(-1)), initiated at four different developmental time points (1, 3, 6, and 9 d post-fertilization [dpf]). Respective induction and competitive inhibition were evaluated over fluorescent images of whole embryo (nonorgan-specific [NOS] EROD activity) and gallbladder (organ-specific [OS] EROD activity). Both flavonoids showed signs of stability in solution. Generally speaking, the mean fluorescence intensity (MFI) values for NOS EROD increased with BNF concentration and exposure challenge. BNF co-exposure with ⩾50 μg ANF L(-1) during the 1-2 and 3-4 dpf challenges lowered NOS EROD to undetectably induced levels. Significant increments in MFIs for OS-EROD were seen from exposures to ⩾2.5 μg BNF L(-1), peaking during the 6-7 dpf challenge regardless of BNF concentration. The simultaneous BNF/ANF incubation showed competitive inhibition for OS EROD activity, although levels were generally detectably induced during all challenges and at all ANF concentrations. The morphometric in vivo gallbladder analysis indicated significant dilation in the 10 dpf-old embryos co-exposed to BNF and 200 μg ANF L(-1). This quantitative approach can be used successfully at 4 dpf at the NOS-EROD or OS-EROD levels, although the NOS-EROD response was sensitive enough to induction or inhibition, even at 2 dpf.

Suppressive effects of benzo[a]pyrene upon fish immune function: evolutionarily conserved cellular mechanisms of immunotoxicity

Knowledge gained through the use of alternative animal models has significantly enhanced our understanding of life at all levels of biological organization. The discipline of toxicology is under considerable pressure to develop such models due to increasing public concern regarding the experimental use of mammals. Studies in this laboratory have focused on the utility of a small laboratory fish model, the Japanese medaka (Oryzias latipes), to investigate immunotoxicological effects of benzo[a]pyrene (BaP). BaP is a ubiquitous environmental contaminant and known mammalian immunotoxicant. This laboratory has demonstrated that in vivo exposure of medaka to BaP (2-200 microg/g BW) significantly depresses both innate and humoral immunity. Further studies have indicated that BaP activates its own biotransformation pathway within medaka immune cells following both in vivo and in vitro exposure. In addition, reduction of BaP metabolism with alpha-naphthoflavone results in the reversal of BaP-induced suppression of antibody production in vitro. Inhibition of CYPlA-mediated metabolism within medaka immune cells also alleviates the immunotoxicity induced by benzo[a]pyrene-7,8-dihydrodiol, but not benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE). This suggests that BPDE may be an ultimate immunotoxicant. Results from this study in medaka are in agreement with previously conducted rodent studies that indicated a role for immunotoxic BaP metabolites in BaP-induced suppression of humoral immunity.

Evaluation of iodine-benzoflavone and ruthenium tetroxide spray reagents for the detection of latent fingermarks at the crime scene

The performance of two spray reagents, iodine-benzoflavone and ruthenium tetroxide (RTX), was evaluated and compared with the conventional technique currently used at the crime scene, that is, powdering. Neither the spray techniques nor powdering were shown to be suitable for all surfaces and ages of marks tested. On some surfaces such as glass and treated wood, powdering was still the superior technique, whereas the spray techniques produced better development on wallpaper, vinyl, and brick. Sequencing work showed that RTX was incompatible with powdering and cyanoacrylate (with a rhodamine 6G stain). Iodine-benzoflavone can be used successfully either before or after powdering in a sequence; however, it was incompatible with cyanoacrylate. Two non-CFC formulations of iodine-benzoflavone using HFC4310mee and HFE7100 solvents were tested and shown not to be as effective as the original Arklone (CFC-113) formulation; however, the HFC4310mee solvent is recommended as the most suitable replacement solvent. Due to the expense of the commercial RTX spray, attempts at formulating a more cost-effective version were also carried out. A formulation was developed that gave comparable development to the commercial version but at a much cheaper cost, and with a shelf life of up to two months. Recommendations are presented for which techniques are suitable for different surfaces and ages of marks. Powdering was shown to be the best technique on all ages of marks tested on treated wood, glass, and also on marks aged three days and older on paint. Iodine-benzoflavone was the best technique on wallpaper, vinyl, brick, and raw wood. RTX was the best detection technique for fresh marks and marks aged up to one day on wallpaper and paint.

Further studies on the lobar heterogeneity in response to coumarin-mediated hepatotoxicity

A randomized sampling protocol coupled with quantitative morphometry has been used to evaluate the inter-lobe variation in centrilobular hepatic necrosis in the mouse, and periportal hepatic necrosis in the beta-naphthoflavone-induced rat, both in response to treatment with coumarin. The results of these studies indicate a random inter-lobe variation in xenobiotic-mediated hepatotoxicity.

Induction in vitro and complete coding region sequence of cytochrome P4501A1 cDNA from cultured whole rat conceptuses during early organogenesis

Exposures of cultured whole rat conceptuses during organogenesis to 3-methylcholanthrene (MC; 0.025-25 microM), 5,6-benzoflavone (BNF; 5-100 microM) or benz[a]anthracene (BA; 5-100 microM) were effected by placement of each of these "MC-type" inducing agents in the culture medium at the time of explantation on day 9.5 of gestation. Conceptuses were then cultured for 48 hr and evaluated on day 11.5 for increased expression of inducible conceptal cytochrome P450 (P450). The three agents each elicited concentration-dependent increases in 7,8-benzoflavone (ANF)-inhibitable ethoxyresorufin O-deethylase (EROD) activities and increased P4501A1 mRNA as detected by primer-specific reverse transcriptase-polymerase chain reaction (RT-PCR) in cell-free preparations of the treated, cultured conceptuses. At effective inducing concentrations, dysmorphogenic or other embryotoxic effects were not detectable. At 20 microM concentrations, the three agents exhibited roughly equal induction that was approximately equivalent in magnitude (6- to 13-fold) to that achieved previously with exposures to MC in utero. Additions to the culture medium of 2.5 to 10 microM concentrations of dexamethasone (DEX) did not alter significantly the magnitude of MC-elicited induction in vitro. Repeated full-length sequencing of an RT-PCR-amplified cDNA revealed a coding region sequence identical to that reported for the P4501A1 sequence from adult rat liver. The results provide a basis for investigations, in the absence of maternal influences, of the regulation of mammalian conceptal P4501A1 in intact tissues during organogenesis, a gestational period critical in terms of the dysmorphogenic and other embryotoxic effects of foreign organic chemicals. The results are also pertinent to studies of embryotoxicity, particularly to the transplacental carcinogenicity, mutagenicity and dysmorphogenicity of P4501A1 substrates.

Mechanism of protection of ebselen against paracetamol-induced toxicity in rat hepatocytes

The protective effect of ebselen (PZ 51), an anti-inflammatory agent, on paracetamol-induced (1 mM) cytotoxicity in hepatocytes freshly isolated from beta-naphthoflavone-pretreated rats was studied. At a concentration of 50 microM added simultaneously with paracetamol, ebselen prevented paracetamol-induced leakage of lactate dehydrogenase (LDH) almost completely and lipid peroxidation (LPO) and depletion of glutathione (GSH) substantially. These protective effects were even more pronounced at 100 microM concentration of ebselen. When added to the hepatocytes 1 hr before paracetamol, 50 microM of ebselen also prevented LDH leakage, LPO and GSH depletion. Reverse addition of paracetamol and ebselen did not result in protection. Simultaneous incubation of 100 microM ebselen and paracetamol inhibited GSH conjugation of paracetamol by more than 50%, however, without any effect on glucuronidation and sulfation of paracetamol. Ebselen was shown not to react directly with paracetamol nor to inhibit cytochrome P450 activity measured as 7-ethoxycoumarin O-deethylase (ECD) activity in the hepatocytes. At mixing, synthetic ebselen selenol and synthetic N-acetyl-p-benzoquinone imine (NAPQI) were shown to form paracetamol and ebselen diselenide. No indication was found for the formation of an ebselen-paracetamol conjugate upon reacting synthetic NAPQI and synthetic ebselen selenol. Reduction of NAPQI, the reactive metabolite of paracetamol, by ebselen selenol is discussed in terms of the mechanism of cytoprotection.

Metabolic activation of the food mutagen 3-amino-1,4-dimethyl-5H-pyrido-[4,3-b]indole (Trp-P-1) in endothelial cells of cytochrome P-450-induced mice

3-Amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) is a carcinogen which is metabolically activated by cytochrome P4501A. This microautoradiographic study showed that there was a highly selective solvent-resistant binding of radioactive substance in endothelial cells of the pulmonary and hepatic portal vascular system and of the vena cava and type 2 pneumocytes 1 day following i.p. or i.v. injection of [3H]Trp-P-1 (100 micrograms/kg) in NMRI mice treated with the cytochrome P4501A-inducing agent beta-naphthoflavone (BNF). In mice treated with indole-3-carbinol, a dietary cytochrome P4501A-inducing factor, a similar binding was observed in the liver but not in the lung. No binding in endothelial cells occurred in vehicle-treated control mice given injections of [3H]Trp-P-1. At incubation of tissues with [3H]Trp-P-1 (0.75 microM) there was also a selective binding of radioactive substance in endothelial cells of the lung and liver and in the vena cava from BNF-treated mice but not from vehicle-treated control mice. Ellipticine but not alpha-naphthoflavone inhibited the endothelial binding in BNF-treated mice exposed to [3H]Trp-P-1 in vivo or in vitro. No binding of radioactive substance occurred in hepatic central veins or in the aorta of BNF-treated mice exposed to [3H]Trp-P-1 in vivo or in vitro. Our data suggest an in situ metabolism of [3H]Trp-P-1 to a reactive species, catalyzed by an BNF-inducible P450 form, possibly 1A1, in endothelial cells. The results of this study and reported heterocyclic amine-induced tumors in the rodent vascular system suggest that endothelial cells are targets for food-derived mutagens.

Cytochrome P450 forms in the rodent lung involved in the metabolic activation of food-derived heterocyclic amines

The metabolic activation of the promutagens 2-amino-3,8- dimethylimidazo[4,5-f]quinoline (IQ), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) by rat and mouse lung microsomes was studied using Salmonella mutagenicity (strain TA98). Lungs from uninduced animals were found to activate all three compounds. A 4-6 fold higher mutagenic activity was obtained with IQ compared to MeIQx and the mutagenic response of PhIP was 1-2 orders of magnitude lower than that of IQ. In order to characterize the forms of P450 in the lung responsible for the metabolic activation of these food mutagens Western blots were performed with microsomes and partially purified P450 fractions from the lung. Western blots revealed the presence of cytochrome P450 2A, 2B and 4A forms in untreated rats. In the lung CYP 1A1 was only detectable after BNF treatment of rats. The CYP 4A isozymes, which have not previously been described in the rat lung, were further identified after PCR amplification from lung mRNA as 4A2 and 4A8. Antibody inhibition studies showed that CYP 2A3 catalyzed a major part (70%) of the metabolic activation of IQ by uninduced rat lung microsomes. The metabolic activation of MeIQx was not influenced by this antibody. An antibody against CYP 2B isozymes also partially inhibited the activation of IQ by uninduced rat lung microsomes. However, since induction of CYP 2B isozymes in the liver by phenobarbital treatment did not increase the metabolic activation of the heterocyclic amines over controls it is unlikely that the rat lung CYP 2B1 is participating in the activation of heterocyclic amines. The inhibition of the IQ-dependent mutagenicity by the CYP 2B antibody is probably due to cross-reaction with CYP 2A3. Alfa-naphthoflavone (ANF), considered to be a specific inhibitor of CYP 1A isozymes at 10 microM, partly inhibited the activation of IQ (30-40%) and MeIQx (60-80%) by uninduced rat and mouse lung microsomes. Upon pretreatment of rats with BNF, lung microsomes activated MeIQx at a rate that was 2-10-fold higher than control lung microsomes, whereas the increase in EROD activity was approximately 100-fold in the same lung preparations. These results suggest that CYP 1A1 may not be the enzyme responsible for the activation of MeIQx in the control rat despite the inhibition with ANF. It is likely that ANF can inhibit other P450 enzymes in the lung, including CYP 2A3.(ABSTRACT TRUNCATED AT 400 WORDS)

Interaction of caffeine with acetaminophen. 1. Correlation of the effect of caffeine on acetaminophen hepatotoxicity and acetaminophen bioactivation following treatment of mice with various cytochrome P450 inducing agents

The combination of caffeine with acetaminophen (APAP) is used widely in the treatment of headache. The effects of caffeine on APAP-induced hepatotoxicity and APAP bioactivation by liver microsomes from uninduced mice and from mice pretreated with various agents that induce cytochrome P450 were studied. When 1 mM caffeine was included, the rate of glutathione-APAP conjugate (GS-APAP) formation was increased significantly by 33 and 39% in microsomes from phenobarbital (PB)- and dexamethasone (DEX)-treated mice, respectively, whereas this parameter was decreased 39 and 12% by caffeine in microsomes from beta-naphthoflavone (beta NF)- and acetone-treated mice, respectively. A 5 mM concentration of caffeine increased GS-APAP formation by 47, 107 and 117% in microsomes from control, PB-, and DEX-treated mice, respectively, and decreased it 39 and 25% in microsomes from beta NF- and acetone-treated mice, respectively. Caffeine was a competitive inhibitor of APAP bioactivation in microsomes from beta NF- and acetone-treated mice. While caffeine increased APAP bioactivation in microsomes from uninduced, PB-, and DEX-treated mice, the apparent Km values for APAP were increased by caffeine, indicating that this enhancement was not due to a direct effect of caffeine on APAP binding to cytochrome P450 but may be due to an effect of caffeine on the substrate-enzyme complex. The variable effect of caffeine on APAP hepatotoxicity correlated with the effect of caffeine on APAP bioactivation by liver microsomes, regardless of pretreatment. Lack of correlation of aminopyrine N-demethylase, but good correlation of erythromycin N-demethylase activity with the extent of caffeine enhancement of APAP bioactivation following PB or DEX treatment suggests that a murine P450 subfamily similar to the rat P450 3A subfamily may be the candidate in mediating the stimulatory effect of caffeine on APAP bioactivation and APAP-induced hepatotoxicity.

Activation of 6-aminochrysene to genotoxic products by different forms of rat liver cytochrome P450 in an O-acetyltransferase-overexpressing Salmonella typhimurium strain (NM2009)

Metabolic activation of a potent mutagen, 6-aminochrysene, to genotoxic products in a newly developed tester strain, Salmonella typhimurium NM2009, was studied in a rat liver microsomal monooxygenase system containing cytochrome P450 (P450). Since the tester strain was constructed by introducing an O-acetyltransferase gene into the original strain S. typhimurium TA1535/pSK1002, it is highly sensitive toward the reactive metabolites of carcinogenic arylamines. DNA-damaging activities of 6-aminochrysene were detected at very low concentrations of substrate (between 0.01 and 0.2 microM) and liver microsomes (from 0.2 to 2 micrograms protein/mL) in the S. typhimurium NM2009 strain. Thus, the potency of genotoxic activities induced by 6-aminochrysene was about 10- to 20-times greater than those induced by the well-known mutagens 2-aminoanthracene and 2-amino-3,5-dimethylimidazo[4,5-f]quinoline. Liver microsomes isolated from rats treated with phenobarbital (PB) and a polychlorinated biphenyl mixture, Kanechlor 500, catalyzed very efficiently the activation of 6-aminochrysene to genotoxic metabolites. Treatment of rats with beta-naphthoflavone (BNF) and with dexamethasone also caused moderate induction of the microsomal activation of 6-aminochrysene. Studies employing immunoinhibition of microsomal catalytic activities and reconstitution with purified P450 enzymes suggested that the most important enzymes involved in the activation of 6-aminochrysene were P450 2B1 and 2B2; other enzymes including P450 1A1 and 1A2 participated to some extent. We also found that the microsomal activation of 6-aminochrysene was catalyzed more effectively in an acetyltransferase-overexpressing strain (NM2009) than in the original TA1535/pSK1002 strain and that these activities could be inhibited by an acetyltransferase inhibitor, pentachlorophenol, in liver microsomes from PB-treated rats, but not in those from BNF-treated rats. These results suggest that the P450/acetyltransferase system is one of the most important catalysts for the activation of 6-aminochrysene in liver microsomes of PB-treated rats, and that activation by BNF-induced P450 enzymes occurs by different mechanisms, probably through the ring oxidation pathway.

Reductase and oxidase activity of rat liver cytochrome P450 with 2,3,5,6-tetramethylbenzoquinone as substrate

The main objective of the present study was to investigate the proposed role of cytochrome P450 in the reductive metabolism of quinones as well as in the formation of reduced oxygen species in liver microsomes from phenobarbital (PB-microsomes) and beta-naphthoflavone (beta NF-microsomes) pretreated rats. In the present study, 2,3,5,6-tetramethylbenzoquinone (TMQ) was chosen as a model quinone. Anaerobic one-electron reduction of TMQ by PB-microsomes showed relatively strong electron spin resonance (ESR) signals of the oxygen-centered semiquinone free radical (TMSQ), whereas these signals were hardly detectable with beta NF-microsomes. Under aerobic conditions TMSQ formation was diminished and concomitant reduction of molecular oxygen occurred in PB-microsomes. Interestingly, TMQ-induced superoxide anion radicals, measured by ESR (using the spin trap 5,5'-dimethyl-1-pyrroline-N-oxide), and hydrogen peroxide generation was found to occur with beta NF-microsomes as well. Furthermore, SK&F 525-A (a type I ligand inhibitor of cytochrome P450) inhibited TMQ-induced hydrogen peroxide formation in both PB- and beta NF-microsomes. However, metyrapone and imidazole (type II ligand inhibitors of cytochrome P450) inhibited molecular oxygen reduction in beta NF-microsomes and not in PB-microsomes. The present study indicates that cytochrome P450-mediated one-electron reduction of TMQ to TMSQ and subsequent redox cycling of TMSQ with molecular oxygen constitutes the major source for superoxide anion radical and hydrogen peroxide generation in PB-microsomes (i.e. from the reductase activity of cytochrome P450). However, most of the superoxide anion radical formed upon aerobic incubation of TMQ with beta NF-microsomes originates directly from the dioxyanion-ferri-cytochrome P450 complex (i.e. from the oxidase activity of cytochrome P450). In conclusion, both the one-electron reduction of TMQ and molecular oxygen were found to be cytochrome P450 dependent. Apparently, both the reductase and oxidase activities of cytochrome P450 may be involved in the reductive cytotoxicity of chemotherapeutic agents containing the quinoid moiety.

Alternatives to Aroclor 1254-induced S9 in in vitro genotoxicity assays

A working party was set up by the UK Environmental Mutagen Society to consider alternatives to Aroclor 1254 (Aroclor)-induced S9 in in vitro genotoxicity assays, with the aims of considering whether a replacement for Aroclor in its role in general screening assays could be readily identified. The working party concluded that there was sufficient support in the literature to justify the use of an appropriate phenobarbital/beta-naphthoflavone regime as an acceptable alternative to Aroclor.

Comparative morphologic and immunohistochemical studies of estrogen plus alpha-naphthoflavone-induced liver tumors in Syrian hamsters and rats

Syrian hamsters were treated with ethinylestradiol and maintained on a diet containing alpha-naphthoflavone (alpha NF), a regimen that produces a high incidence of liver tumors. Morphologic analyses (light microscopy, immunoperoxidase studies, and electron microscopy) were performed on livers of these animals. After 4 months of hormone plus alpha NF treatment, marked hepatocyte cell changes were already present, as demonstrated by loss of eosinophilic staining of hepatocyte cytoplasm. Large multinucleated hepatocytes exhibiting frequent mitoses were observed around central veins. After 5 months of treatment, there was proliferation of bile ducts, and small cells with eosinophilic cytoplasm resembling hepatocytes appeared surrounding these bile ducts. At 7 to 8 months, the first tumor nodules (foci) were seen. Tumor foci in the portal area consisted of small clusters of large cells resembling hepatocytes with irregular nuclei. At the same time, dysplastic glands were identified among proliferating bile ducts. By 8 to 10 months, large tumors were present. These were trabecular hepatocellular carcinomas with widely varying individual cell morphology. Compared with adjacent liver, dysplastic glands in the portal areas, microcarcinomas, and large tumors all showed intense immunostaining for cytokeratin. Rats treated with the same regimen also developed hepatic tumors, but the light and electron microscopy results and immunohistochemical profiles were very different. Altered hepatic foci composed of small hepatocytes were typically prominent; however, malignant tumors did not arise from the portal area. Neither altered foci nor tumors stained significantly for cytokeratin. These data suggest that the biochemical events giving rise to these liver tumors differ between the species studied, despite the animals being exposed to the same treatment regimens.

Determination of multiple forms of cytochrome P-450 in microsomes from the digestive gland of Cryptochiton stelleri

Polyclonal antibodies raised against purified trout cytochromes P-450 (P-450) LM2 (anti-LM2) and LM4b (anti-LM4b) were used in Western blot analyses with digestive gland microsomes from control and beta-naphthoflavone (BNF)-treated gumboot chitons Cryptochiton stelleri. An increase and decrease in staining intensity subsequent to treatment with anti-LM4b and anti-LM2, respectively, was observed in digestive gland microsomes from BNF-treated chiton. Thus, there appears to be at least two forms of P-450 in microsomes from the digestive gland of Cryptochiton; one of which is induced by BNF and perhaps is involved in benzo(a)pyrene (BP) biotransformation, and another form which is inhibited by BNF.

Intraperitoneal mesotheliomas induced in mice by a polycyclic aromatic hydrocarbon

Female mice of 6 strains (C3H/HeN, BALB/c, C57BL/6N, DBA/2, NIH Swiss, and AKR/N) were given the polycyclic aromatic hydrocarbon carcinogen 3-methylcholanthrene (MC) intragastrically in olive oil at a dose of 20 mg/kg, weekly for 12 wk. Half were pretreated 24 h before each MC administration with intraperitoneal beta-naphthoflavone (beta-NF, 150 mg/kg in olive oil), a noncarcinogenic inducer of certain cytochrome P-450 isozymes. Remaining mice were given olive oil prior to MC in the same fashion, or beta-NF in olive oil or olive oil alone without subsequent exposure to MC. All mice were killed when moribund or 13 mo after the start of treatment. Most of the mice, irrespective of treatment, exhibited signs of peritoneal injury, including inflammation, necrosis, granuloma formation, and mineralization. Mice of some of the strains also presented peritoneal mesotheliomas, in addition to a variety of other tumors. The incidence of unequivocal mesothelioma-bearing mice was 12/31 C3H/He and 9/32 BALB/c mice given only MC. Incidence was low in C57BL/6 (1/31) and DBA/2 (1/26), and no definite mesotheliomas were found in Swiss or AKR mice. There were in addition a number of cases of sarcoma (nine total in all strains) and of peritonitis (four total) that resembled mesothelioma to some degree and were initially diagnosed as much. beta-NF pretreatment reduced the frequency of mesotheliomas: there was only one definite mesothelioma in any of the beta-NF-MC groups, in a C3H/He mouse. Most of the mesotheliomas were mixed fibro-mesothelial type, sometimes with papillary epithelial excrescences. They typically grew in a botryoid pattern within the peritoneal cavity, coating the abdominal organs and sometimes actively invading these organs and the diaphragm. Some lesions exhibited pleomorphism, prominent giant cells, and frequent mitoses. In addition, several lesions consisting of severe mesothelial hyperplasia associated with tissue necrosis and inflammation were considered as possible early stages of mesothelioma development. It was postulated that peritoneal injury imposed by repeated intraperitoneal injection of oil acted as an enhancing factor for mesothelioma induction by MC. The pertinence of such a relationship to mechanisms in the etiology of human mesotheliomas is discussed.

The first identification of the benzenediazonium ion formation from a non-aminoazo dye, 1-phenylazo-2-hydroxynaphthalene (Sudan I) by microsomes of rat livers

1-Phenylazo-2-hydroxynaphthalene (Sudan I) is converted by microsomal enzymes of rat livers in vitro to 5 products. Hepatic microsomes from 5,6-benzoflavone-treated rats are more effective for the metabolism of Sudan I than those from phenobarbital- or Sudan I alone-treated rats. Major products formed by microsomes are identified as the ring-hydroxyderivatives of benzene and naphthalene rings. The formation of the benzenediazonium ion evolved by oxidative splitting of the azo group of Sudan I by microsomal enzymes is also proved. The oxidative splitting of Sudan I by microsomal enzymes may be considered as the possible mechanism of the Sudan I activation to the ultimate carcinogen (benzenediazonium ion).

Effects of 5-bromo-2-deoxyuridine concentration and alpha-naphthoflavone on the association between smoking and the frequency of sister-chromatid exchanges in lymphocytes from maternal and cord blood

The frequency of sister-chromatid exchanges was analyzed in maternal and cord blood lymphocytes obtained at delivery from 23 nonsmokers and 21 smokers. Lymphocytes were cultured under 3 conditions: in the presence of 100 microM 5-bromo-2-deoxyuridine (BUdR), 20 microM BUdR and 20 microM BUdR with 40 microM alpha-naphthoflavone (ANF). Under all assay conditions, frequencies of SCEs were consistently higher for maternal lymphocytes than for cord lymphocytes. There was no association between SCE values for cultures of the same blood specimen with 100 microM BUdR and 20 microM BUdR. When cultured with 100 microM BUdR, maternal lymphocytes from smokers had a mean SCE frequency of 13.5, which was significantly higher than the value of 11.1 observed for nonsmokers (p = 0.001 by the Wilcoxon rank sum test). Maternal smoking had no significant effect on overall frequencies of SCEs in maternal blood cultured with 20 microM BUdR either with or without ANF or when the differential between cells cultured with and without ANF was considered. Use of caffeinated beverages was associated with increased SCE values for maternal lymphocytes cultured with 20 microM BUdR (Tau beta = 0.36, p = 0.02 for the Kendall's Rank Correlation), but no such association was seen with 100 microM BUdR. For cord blood lymphocytes, however, neither smoking nor caffeine use were associated with SCE values obtained by any of the assay conditions used. The findings suggest that results of human monitoring studies using SCEs could differ depending on the concentration of BUdR used in cultures.

[Visualization of latent fingerprints on porous and nonporous materials using iodine-benzoflavone aerosol]

A method is described for the detection of latent fingerprints on both porous and non-porous materials employing iodine and 7,8-benzoflavone while using dichloromethane and "frigen-113" as solvents. In some cases the method could be useful for field-investigation.

4-Hydroxylation of nitrofurantoin in the rat. A 3-methylcholanthrene-inducible pathway of a relatively nontoxic compound

When nitrofurantoin was administered daily to rats, the urinary excretion of unmetabolized drug was significantly decreased after induction by 3-methylcholanthrene or beta-naphthoflavone, but was not altered after treatment with phenobarbital. In urine samples taken 36 hr after a single dose of 14C-nitrofurantoin in rats induced with 3-methylcholanthrene, the total excretion of radioactivity (30% of dose) was the same as in noninduced rats. The proportion of unchanged nitrofurantoin, however, was only 33% of the radioactivity recovered in urine from 3-methylcholanthrene-treated animals whereas in urine from control animals 76% of the activity could be attributed to the unmetabolized drug. In 6-hr urine samples one metabolite was present to a detectable extent only in urine from 3-methylcholanthrene-treated animals. The metabolite was identified as the 4-hydroxy derivative of nitrofurantoin. 4-Hydroxylation of nitrofurantoin may find use as indicator reaction for a 3-methylcholanthrene-type induction state under in vivo conditions.

Biochemical basis for the resistance of guinea-pig and monkey to the carcinogenic effects of arylamines and arylamides

1. Ag.l.c. assay for N-hydroxy-2-acetamidofluorene has been modified to measure both N-hydroxy-2-acetamidofluorene and N-hydroxy-2-aminofluorene. 2. Like guinea-pig, monkey N-hydroxylates both 2-aminofluorene and 2-acetamido-fluorene. The N-hydroxy metabolites are rapidly further metabolized even in the presence of inhibitors of deacetylase. The exact nature of this further metabolism is still unknown. Preliminary evidence indicates that, at least in the guinea-pig, 7-hydroxy-2-acetamidofluorene may be a metabolite of N-hydroxy-2-acetmidofluorene. 3. 3-Methylcholanthrene, 7,8-benzoflavone and miconazole, which have been shown to inhibit guinea-pig liver microsomal N-hydroxylase, do not significantly inhibit the monkey liver enzyme. 4. 2-Acetamidofluorene, which inhibits the guinea-pig liver microsomal N-hydroxylation of 2-aminofluorene in vitro, activates the enzyme from monkey liver. This activation, which is dose-dependent, appears to be allosteric. 5. Both guinea-pig and monkey are more efficient in N-hydroxylating 2-aminofluorene than 2-acetamidofluorene. The affinity (in term of apparent KM) of the guinea-pig liver enzyme is 4 times greater than the affinity of the monkey liver enzyme.

Effect of phenobarbital treatment and cytochrome P-450 inhibitors on the laurate omega- and (omega - 1)-hydroxylase activities of rat liver microsomes

The omega- and (omega - 1)-hydroxylase activities for lauric acid were investigated in rat liver microsomes. Treatment of rats with phenobarbital selectively induced the hydroxylation of the fatty acid (omega - 1)-hydroxylase activity two- to threefold, but had little effect on the omega-hydroxylation reaction. SKF 525-A, metyrapone, and alpha-naphthoflavone inhibited (omega - 1)-hydroxylation, but had only neglible effects on omega-hydroxylation. Metyrapone at 10(-4) inhibited the specific activity of (omega - 1)-hydroxylase 70% in phenobarbital-pretreated rats, but produced only a 10% inhibition of the omega-hydroxylation activity. alpha-Naphthoflavone at 10(-4)M inhibited (omega - 1)-hydroxylase activity 60% in untreated and beta-haphthoflavone-pretreated rats, while omega-hydroxylase activity was decreased only 20%. A selective effect was also observed when microsomes were stored overnight at 4 degrees C. Declines of 50% and 70% were observed in the (omega - 1)-hydroxylase activities after 24 and 48 hr, respectively, whereas omega-hydroxylation decreased only 10-20%. The differential effects on omega- and (omega - 1)-hydroxylase activities of a variety of conditions suggest that distinct cytochromes P-450 mediate the two fattty acid hydroxylases in liver microsomes.

Metabolism and formation of DNA adducts of benzo(a)pyrene in human diploid fibroblasts

Cultured human diploid skin fibroblasts incubated with [G-3H]benzo(a)pyrene yielded about 10 times more H2O-=soluble benzo(a)pyrene metabolites and DNA adducts of stationary growth phase than did proliferating cultures. This increased formation could be blocked by alpha-naphthoflavone. Trichloropropenoxide and cyclohexenoxide, inhibitors of the epoxide hydratase, inhibited predominantly the formation of DNA adducts. Cultures from older individuals formed significantly more benzo(a)pyrene metabolites and DNA adducts, but control cultures from patients with either lung cancer or melanoma did not. The age influence was not apparent when the ratio of DNA adducts to H2O-soluble metabolites was determined for each individual cell line. However, the proportion of DNA-bound material in the cells from patients with lung cancer was significantly increased compared to cells from melanoma patients or healthy individuals.

Quinoline: conversion to a mutagen by human and rodent liver

Quinoline, a hepatocarcinogen in rats, and 23 quinoline derivatives were tested for mutagenic activity with the Ames Salmonella typhimurium assay. Quinoline, 5-hydroxyquinoline, and 8-hydroxyquinoline were mutagenic in strain TA 100 when Aroclor 1254-induced rat (male outbred Sprague-Dawley) liver homogenate was present in the incubation mixture. Enzyme preparations from rats pretreated with P-448-dependent aryl hydrocarbon hydroxylase inducers [3-methylcholanthrene (MCA) and beta-naphthoflavone] and MCA-treated "responsive" C57BL mice also metabolized quinoline to a mutagen, but phenobarbital and pregnenolone-16alpha-carbonitrile pretreatment did not yield active preparations. The mutagenicity of quinoline was blocked by the in vitro addition of menadione, butylated hydroxytoluene, alpha-naphthoflavone, vitamin A acetate, and glutathione to the test system. Depletion of glutathione by diethyl maleate pretreatment in vivo enhanced the mutagenic potential of the liver enzyme preparation. Mutagenic activity was correlated to the formation of water-soluble quinoline metabolites, and we suggested that the reactive quinoline intermediate is quinoline-2,3-epoxide. Microsomal enzymes isolated from human liver tissue, but not lung tissue, also converted quinoline to a mutagen.

alpha-Naphthoflavone activation of 6-hydroxymethylbenzo(alpha)pyrene synthetase

alpha-Naphthoflavone activates the aryl hydroxymethyl synthetase of both the microsomal membrane-bound and soluble enzymes of rat liver and rat lung. The enzyme catalyzes the hydroxymethylation of benzo(alpha)pyrene to the 6-hydroxymethyl derivative.