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G E Neal

Publications and source records attributed to G E Neal.

At least 55 records · Page 3Linked to original sources
PubMed1992

Molecular cloning and heterologous expression of a cDNA encoding a mouse glutathione S-transferase Yc subunit possessing high catalytic activity for aflatoxin B1-8,9-epoxide.

Resistance to the carcinogenic effects of aflatoxin B1 (AFB1) in the mouse is due to the constitutive expression of an Alpha-class glutathione S-transferase (GST), YcYc, with high detoxification activity towards AFB1-8,9-epoxide. A cDNA clone (pmusGST Yc) for a murine GST Yc polypeptide has been isolated. Sequencing has shown the cDNA insert of pmusGST Yc to be 922 bp in length, with an open reading frame of 663 bp that encodes a polypeptide of M(r) 25358. The primary structure of the murine GST Yc subunit predicted by pmusGST Yc is in complete agreement with the partial amino acid sequence of the aflatoxin-metabolizing mouse liver GST described previously [McLellan, Kerr, Cronshaw & Hayes (1991) Biochem. J. 276, 461-469]. A plasmid, termed pKK-musGST Yc, which permits the expression of the murine Yc subunit in Escherichia coli, has been constructed. The murine GST expressed in E. coli was purified and found to be catalytically active towards several GST substrates, including AFB1-8,9-epoxide. This enzyme was also found to possess electrophoretic and immunochemical properties closely similar to those of the GST Yc subunit from mouse liver. However, the GST synthesized in E. coli and the constitutive mouse liver Alpha-class GST exhibited small differences in their chromatographic behaviour during reverse-phase h.p.l.c. Automated Edman degradation revealed alanine to be the N-terminal amino acid in the GST Yc subunit expressed in E. coli, whereas the enzyme in mouse liver possesses a blocked N-terminus. Although sequencing showed that the purified Yc subunit from E. coli lacked the initiator methionine, the amino acid sequence obtained over the first eleven N-terminal residues agreed with that predicted from the cDNA clone, pmusGST Yc. Comparison of the deduced amino acid sequence of the mouse Yc polypeptide with the primary structures of the rat Alpha-class GST enzymes revealed that it is more closely related to the ethoxyquin-induced rat liver Yc2 subunit than to the constitutively expressed rat liver Yc1 subunit. The significance of the fact that both mouse Yc and rat Yc2 exhibit high catalytic activity towards AFB1-8,9-epoxide, whereas rat Yc1 possesses little activity towards this compound, is discussed in terms of structure/function.

Aflatoxin B1↗
PubMed1992

Sequential study of the chronic nephrotoxicity induced by dietary administration of ethoxyquin in Fischer 344 rats.

Groups of 3-week-old male and female Fischer 344 rats were administered 0.5% ethoxyquin-containing diet for varying periods of time, ranging from 4 weeks up to 18 months, to assess renal histopathology. The primary lesion observed was renal papillary necrosis in the male rat, commencing as interstitial degeneration of the papillary tip by 4 weeks exposure, and reaching a complete form of papillary necrosis by 24 weeks. The papillary necrosis in male rats was consistently accompanied by active pyelonephritis affecting the cortex, and urothelial hyperplasia in the renal pelvis. A marked sex difference was evident in that female rats developed papillary change at a later stage than males and the lesion never progressed beyond interstitial degeneration. A further sex difference associated with ethoxyquin treatment was the increasing cellular accumulation of lipofuscin-related pigment involving proximal tubules in female rats. Spontaneous chronic progressive nephropathy (CPN) was exacerbated by ethoxyquin in both males and females, but more so in the former. Proximal tubule hyperplasia was most frequently observed in ethoxyquin-treated males at the later sampling times. In all cases, such proliferative lesions were associated either with pyelonephritis or with the most advanced stages of CPN. Contrary to a previous report, there was no evidence that ethoxyquin directly induced preneoplastic renal tubule hyperplasia.

Animals↗
PubMed1992

Effect of dietary protein level on aflatoxin B1 actions in the liver of weanling rats.

The hepatocarcinogenic responses of rats to aflatoxin B1 (AFB1) are believed to depend on microsomal activation of the toxin, followed by macromolecular binding. Dietary protein insufficiency is reported to reduce the level of microsomal metabolism, and therefore would be expected to reduce the AFB1-induced carcinogenicity. Indeed, diminished hepatocarcinogenicity in low-protein diet fed weanling rats that had received AFB1 has been reported. In the present study, carcinogenicity and other toxic effects of AFB1 (0.5 p.p.m.) fed to weanling male Fischer F344 rats on a low-protein diet (5%) or normal-protein (20%) diet for up to 8 weeks were examined. In our study, in contrast with the previous report, all animals that had survived some initial toxicity were found to have developed hepatic tumors or hyperplastic gamma-glutamyltransferase-positive foci a year later. The low-protein diet also produced sub-acute toxicity after AFB1 exposure in the weanling rats, leading to severe histological changes, and the death of about half the animals after 3-4 weeks of exposure. Animals fed an AFB1-containing normal-protein diet also exhibited AFB1-induced hepatocarcinogenicity, but not the sub-acute toxicity. The levels of hepatic enzymes involved in AFB1 metabolism were examined in animals fed the low- or normal-protein diets in the absence of AFB1. The low-protein diet, fed to 3 week weanlings for the subsequent 5 weeks, decreased hepatic cytochrome P450 levels, as well as the in vitro capacity of microsomal fractions to form AFB1-8,9-dihydrodiol, an index of AFB1-8,9-epoxide formation. Rats on a normal-protein diet did not show these changes. This discrepancy between the observed increase in sub-acute toxicity and decrease in microsomal activities in the low-protein fed animals implies that the toxic effects observed in these rats were not directly related to metabolic activation of the toxin. In contrast to the diminished microsomal in vitro AFB1 activation, however, in vivo AFB1-DNA adduct formation ability in rats receiving the low-protein diet in the absence of AFB1 was found to become elevated more rapidly during the 5 week experimental feeding period, compared with animals receiving the normal-protein diet. This was accompanied by a more rapid fall in the levels of AFB1-glutathione S-transferase isozyme activity in the low-protein fed animals. The results of this study on weanling rats support the importance of AFB1-GSH in protecting against the carcinogenic responses to AFB1, and probably also the sub-acute toxicity of the latter.(ABSTRACT TRUNCATED AT 400 WORDS)

Aflatoxin B1↗
PubMed1992

Ethinyl estradiol-induced cell proliferation in rat liver. Involvement of specific populations of hepatocytes.

Hepatocyte proliferation was analyzed in vivo during the time course of continuous administration to rats of the liver tumor promoter ethinyl estradiol (EE) at 10 p.p.m. in the diet. EE-induced acute liver hyperplasia was detected in male and female Sprague-Dawley rats as an increased mitotic index of hepatocytes after 2 days of treatment. 5'-Bromodeoxyuridine (BrdU) labeling showed that proliferating hepatocytes were randomly distributed throughout the hepatic lobule. Subsequently, and still during the first few days of continuous EE treatment, hepatocyte proliferation decreased to control levels, and a transient increase in the incidence of apoptosis in the liver was detected. Although consistent with the concept of liver growth regression after mitogen-induced hyperplasia, these results differ from others reported to date in that, in our experiments, the cessation of cell proliferation and the subsequent growth regression occurred without withdrawal of EE in our experiments. After returning to control levels, hepatocellular proliferation again increased between 3 and 6 months of chronic treatment and remained activated during the following months of continuous treatment, as seen by accumulative BrdU labeling. Proliferating hepatocytes were predominantly located in zone 2 of the hepatic lobule at this time, surrounding a periportal zone of vacuolated hepatocytes, which were also induced by the treatment. Moreover, hyperplasia of basophilic hepatocytes was also seen around some portal spaces. In another set of experiments, chronic EE-induced activation was characterized by flow cytometry on hepatocytes isolated from male Fischer rats. Ploidy analysis of hepatocyte cell suspensions showed that the normal polyploid pattern of hepatocytes was altered by EE, the proportion of diploid hepatocytes rising considerably. The results also showed that these diploid cells were the most susceptible hepatocyte population to EE-induced proliferation, as shown by a combination of BrdU labeling and cell sorting methods. In contrast to Sprague-Dawley rats, no vacuolated cells were found histologically in the livers of these animals and the proliferating hepatocytes were located adjacent to the portal areas. These results taken together support the existence of cell target populations in the liver responding to the effects of tumor promoters. The finding that a subpopulation of diploid hepatocytes was the liver cell class most susceptible to proliferation during chronic EE treatment may explain, at least in part, the behavior of EE as a tumor promoter in hepatocarcinogenesis.

Animals↗
PubMed1991

Ethoxyquin-induced resistance to aflatoxin B1 in the rat is associated with the expression of a novel alpha-class glutathione S-transferase subunit, Yc2, which possesses high catalytic activity for aflatoxin B1-8,9-epoxide.

A purification scheme has been devised for two ethoxyquin-inducible Alpha-class glutathione S-transferases (GSTs) which possess at least 25-fold greater activity towards aflatoxin B1 (AFB1)-8,9-epoxide than that exhibited by the GSTs (i.e. F, L, B and AA) that have been described previously. These two enzymes are both heterodimers and both contain a subunit of Mr 25,800. This subunit has been isolated from both of the GST isoenzymes and, after cleavage with CNBr, it has been subjected to automated amino acid sequencing. The primary structure of the Mr 25,800 subunit revealed that it forms part of a subfamily of Alpha-class GSTs which possess closest identity (about 92%) with the Yc subunit of apparent Mr 27,500, which is encoded by the recombinant cDNA clone pGTB42 [Telakowski-Hopkins, Rodkey, Bennett, Lu & Pickett (1985) J. Biol. Chem. 260, 5820-5825]. As these two GSTs possess less than 70% sequence identity with the Ya1 and Ya2 subunits, both of Mr 25,500, the constitutively expressed Yc subunit of Mr 27,500 has been renamed Yc1 and the ethoxyquin-inducible GST of Mr 25,800 has been designated Yc2. Using this nomenclature, the two GSTs with high activity for AFB1-8,9-epoxide are Ya1Yc2 and Yc1Yc2. Although evidence suggests that induction of Yc2 is responsible for the high detoxification capacity of livers from ethoxyquin-treated rats for AFB1-8,9-epoxide, resistance towards AFB1 may be multifactorial in this instance as dietary ethoxyquin also induces the Ya1, Ya2 and Yc1 subunits about 2.2-, 10.9- and 2.7-fold respectively. Besides the induction of GST by ethoxyquin, activity towards AFB1-8,9-epoxide is also elevated in the livers of neonatal rats and in livers that contain preneoplastic nodules. Western blotting experiments show that Yc2 is not present in hepatic cytosol from adult rats fed on normal diets but is expressed in neonatal rat livers and in the livers of adult rats that contain preneoplastic nodules that have arisen as a consequence of consuming diets contaminated with AFB1.

Aflatoxin B1↗
PubMed1991

Investigation of the assay of AFB1-albumin adducts using proteolysis products in ELISA.

Epidemiological evidence of the involvement of aflatoxins in the aetiology of human liver cancer has led to an increasing interest in the development of appropriate techniques for monitoring human exposure. The assay for aflatoxin adducts in albumin has a better potential for assessing long-term exposure than analyses of urine samples, and several protocols for ELISA of these adducts, following proteolysis of albumin, have been examined. However, there is usually an incomplete release of a major adduct, aflatoxin-lysine, even after prolonged hydrolysis, and the adduct is very unstable under some conditions of proteolysis for unknown reasons. Therefore, before such techniques can be recommended for general application, the significance of such factors in the quantitive estimation of aflatoxin adducts needs to be evaluated. This study has detected the presence of a considerable fraction of aflatoxin-modified material, produced by proteolysis of in vivo aflatoxin-modified rat albumin or in vitro modified bovine albumin, and which is not recognized in ELISA by an anti-aflatoxin polyclonal antibody having a wide spectrum of aflatoxin metabolite detection. This fraction increases in parallel with the proteolysis protocols.

Aflatoxin B1↗
PubMed1991

Contribution of the glutathione S-transferases to the mechanisms of resistance to aflatoxin B1.

The harmful effects of Aflatoxin B1 (AFB1) are a consequence of it being metabolized to AFB1-8,9-epoxide, a compound that serves as an alkylating agent and mutagen. The toxicity of AFB1 towards different cells varies substantially; sensitivity can change significantly during development, can be modulated by treatment with xenobiotics and is decreased markedly in preneoplastic lesions as well as in tumors. Three types of resistance, namely intrinsic, inducible and acquired, can be identified. The potential resistance mechanisms include low capacity to form AFB1-8,9-epoxide, high detoxification activity, increase in AFB1 efflux from cells and high DNA repair capacity. Circumstantial evidence exists that amongst these mechanisms the glutathione S-transferases, through their ability to detoxify AFB1-8,9-epoxide, play a major role in determining the sensitivity of cells to AFB1.

Aflatoxin B1↗
PubMed1991

An examination of the effect of pretreatment of rats with Sacoglottis gabonensis bark extract, a Nigerian palmwine additive, and ethanol on macromolecular binding of aflatoxin B1.

In a previous study (Okoye and Neal, Food and Chemical Toxicology 1988, 26, 679) enhanced ethanol-induced reductions in albumin-bound and unbound serum aflatoxin B1 (AFB1) and increased hepatic DNA-AFB1 binding were observed in rats treated with bark extract of Sacoglottis gabonensis, a Nigerian palmwine additive. The present study was designed to examine further the mechanism of these effects. Male weanling rats were pretreated with the bark extract or ethanol, or both, in drinking-water (at three times the levels used in the previous study) for 8 days before the ip administration of a single dose of [3H]AFB1. [In the previous study the rats were fed all three compounds simultaneously.] In contrast to the results of the previous study, when both the additive and ethanol were administered, there were no significant effects on [3H]AFB1 binding to liver or serum albumin or liver DNA. The levels of DNA-bound aflatoxin were reduced in rats given the additive or ethanol alone.

Aflatoxin B1↗
PubMed1991

The isolation and culture of DHBV-infected embryo and duckling hepatocytes and the effect of aflatoxin B1 or irradiation on these cells.

The preparation of primary cultures of control and DHBV-infected duck hepatocytes from embryos and young ducklings is described. Cultures of both embryo and duckling hepatocytes secreted duck serum proteins. Cultures of hepatocytes established from ducklings maintained initial morphology for up to 3 weeks in culture and also exhibited high levels of metabolism of aflatoxin B1. Embryonic cell cultures rapidly lost ability to metabolise AFB1 and became overgrown by spindle-shaped cells. Both embryo and duckling cell cultures secreted infective DHBV, and had intracellular replicative forms of the virus. No integration of the virus into the duck genome was observed, and attempts to induce viral integration in the duckling hepatocytes using irradiation and aflatoxin B1 toxicity were unsuccessful. The results of the study lend further support to the suggestion that the rarity of liver cancer in DHBV-infected experimental ducks is related to an innate resistance of the hepatocytes to develop DHBV-DNA integration. Another possibility may be related to the lower oncogenic potential of the DHBV strain used for the study. However DHBV infected duckling hepatocytes would appear to offer a suitable material for studying viral replication and mechanisms of aflatoxin B1 toxicity during prolonged cell culture.

Aflatoxin B1↗
PubMed1991

Possible effect of infection with liver fluke (Opisthorchis viverrini) on the monitoring of urine by enzyme-linked immunosorbent assay for human exposure to aflatoxins.

Several laboratories have initiated studies to assess human exposure to aflatoxin at an individual level by measuring aflatoxin metabolites in the urine by immunoassay. The fact that the antibodies recognize a variety of metabolites, albeit with differing affinities, means that any environmental factor that modifies the pattern of urinary metabolites associated with a given exposure could affect quantification in immunoassay. We have examined two such possible effects: (i) the pattern of metabolites after a dose of 14C-aflatoxin B1 in rats and (ii) the pattern of metabolites in hamsters and humans with and without exposure to liver flukes. We found no dose-related effect on the pattern of urinary metabolites over a 250-fold range, but there was a significant increase in the proportion of water-soluble aflatoxin metabolites in hamsters infected with liver fluke over that in uninfected animals. In human urine samples, there also appeared to be a difference in the metabolites in individuals infected with liver fluke from those in uninfected persons. These observations are relevant to both mechanistic and monitoring aspects of research into aflatoxins.

Aflatoxins↗
PubMed1990

The preparation of highly enriched fractions of binucleated rat hepatocytes by centrifugal elutriation and flow cytometry.

A procedure is described for the isolation of highly enriched fractions of binucleated hepatocytes from rat liver. Liver cells isolated by EGTA and collagenase perfusion were initially subjected to centrifugal elutriation and second to flow cytometry coupled with Hoechst 33342 staining. The elutriation step yielded hepatocyte fractions which contained almost entirely mononuclear diploid cells and fractions enriched in binucleate hepatocytes. The fractions with the highest proportion of binucleated hepatocytes contained between 50 and 56% of these cells. Subsequent flow cytometric cell sorting yielded fractions which contained greater than 80% binucleated cells. These cells were viable in culture as demonstrated by the immunohistochemical detection of bromodeoxyuridine incorporation.

Aneuploidy↗
PubMed1990

Preferential over-expression of the class alpha rat Ya2 glutathione S-transferase subunit in livers bearing aflatoxin-induced pre-neoplastic nodules. Comparison of the primary structures of Ya1 and Ya2 with cloned class alpha glutathione S-transferase cDNA sequences.

Normal rat liver expresses Ya (Mr 25,500), Yc (Mr 27,500) and Yk (Mr 25,000) Class Alpha glutathione S-transferase (GST) subunits. The Ya-type subunit can be resolved into two separate polypeptides, designated Ya1 and Ya2, by reverse-phase h.p.l.c. In rat livers that possess aflatoxin B1-induced pre-neoplastic nodules, a marked increase is observed in the expression of Ya1, Ya2, Yc and Yk; of these subunits, Ya2 exhibited the greatest increase in concentration. The Ya1 and Ya2 subunits isolated from nodule-bearing livers were cleaved with CNBr, and the purified peptides were subjected to automated amino-acid-sequence analysis. Differences in the primary structures of the two Ya GST subunits were found at positions 31, 34, 107 and 117. These data demonstrate that Ya1 and Ya2 are distinct polypeptides and are the products of separate genes. The amino acid sequences obtained from Ya1 and Ya2 were compared with the cloned cDNAs pGTB 38 [Pickett, Telakowski-Hopkins, Ding, Argenbright & Lu (1984) J. Biol. Chem. 259, 4112-4115] and pGTR 261 [Lai, Li, Weiss, Reddy & Tu (1984) J. Biol. Chem. 259, 5182-5188], which encode rat Ya-type subunits. From these comparisons it appears probable that Ya1 represents the GST subunit encoded by pGTR 261, whereas Ya2 represents the subunit encoded by pGTB 38. It is likely that the over-expression of Ya1 and Ya2 in nodule-bearing livers is of major significance in the acquired resistance of nodules to aflatoxin B1, since previous work [Coles, Meyer, Ketterer, Stanton & Garner (1985) Carcinogenesis 6, 693-697] has shown that the Ya-type GST subunit has high activity towards aflatoxin B1 8,9-epoxide.

Aflatoxins↗
PubMed1990

Sensitivity of the cell cycle to TGF beta 1 does not correlate with transformation of a rat liver epithelial cell line.

The effects of TGF beta 1 on cell cycle events in a rat liver derived epithelial cell line (BL9) and in two in vitro transformants of this line were studied by flow cytometry. Using either ethidium bromide staining or the incorporation of bromodeoxyuridine to evaluate DNA synthesis it was shown that TGF beta 1 prevented the entry of G0/G1 phase BL9 cells into S phase. TGF beta 1 did not exert its inhibitory effect(s) on DNA synthesis by the modulation of early events in the cell cycle. The tumorigenic transformed BL9 cell lines gave contrasting responses to the effects of TGF beta 1. DNA synthesis in a BL9 cell line derived by transfection with an active N-ras oncogene was unaffected by TFG beta 1 and thus appeared refractory to its growth controlling effects. On the other hand cells from a BL9 cell line derived by in vitro transformation with activated aflatoxin B1 retained their sensitivity to the effects of TGF beta 1. Thus the loss of the inhibitory effect of TGF beta 1 on DNA synthesis is not obligatory for the malignant transformation of rat liver epithelial cells.

Animals↗
PubMed1990

Evidence for involvement of multiple forms of cytochrome P-450 in aflatoxin B1 metabolism in human liver.

Liver cancer is a major cause of premature death in many areas of Africa and Asia and its incidence is strongly correlated with exposure to aflatoxin B1 (AFB1). Because AFB1 requires metabolic activation to achieve a biological response, there is a need for detailed knowledge of the mechanism of activation to assess individual risk. We have carried out an extensive study using a total of 19 human liver samples to determine the individual variability in the metabolism of the toxin to mutagenic or detoxification products and to identify the specific cytochrome P-450 forms involved in these processes. Metabolism to the toxic 8,9-epoxide or to products mutagenic in the Ames test was found to exhibit very large individual variation. The rates of metabolic activation were highly correlated with both the level of proteins of the P450IIIA gene family and with the total cytochrome P-450 content of the microsomes. In agreement with this, antibodies reacting with P450IIIA proteins were strong inhibitors of both the metabolism and mutagenicity in the majority of the samples. However, the inhibition varied between 50% and 100%. The expression of a protein in the P450IIC gene family also correlated with AFB1 metabolism and mutagenicity. This result therefore indicated the involvement of cytochromes other than P450IIIA in the activation of AFB1 by human liver microsomes. This hypothesis was strongly supported by the finding that antibodies to P450IA2 and P450IIA1 were also effective inhibitors of metabolism in many of the samples. These data demonstrate that, although P450IIIA probably plays an important role in AFB1 activation, several other cytochrome P-450 forms have the capacity to activate the toxin. Similar considerations apply to detoxifying metabolism to aflatoxin Q1 and aflatoxin M1. The levels of expression of many of the forms of cytochrome P-450 involved in AFB1 metabolism are known to be highly sensitive to environmental factors. This indicates that such factors will be an important determinant in individual susceptibility to the tumorigenic action of AFB1.

Aflatoxin B1↗
PubMed1990

Glutathione S-transferase localization in aflatoxin B1-treated rat livers.

Overexpression of detoxication enzymes is associated with the development of drug-resistant, preneoplastic nodules in the carcinogen-treated rat liver. The most consistent marker of preneoplasia in many experimental models is increased expression of the pi-class glutathione S-transferase (GST) YfYf. We have confirmed by immunostaining that the pi-class GST is overexpressed in aflatoxin B1-induced preneoplastic nodules and liver tumours in rats. However, pi-class GST YfYf has low activity against aflatoxin B1-8,9-epoxide, and most activity against this cytotoxic and genotoxic metabolite is associated with the alpha-class GSTs YaYa, YaYc and YcYc. We have demonstrated that there is also a consistent increase in the alpha-class GSTs in this model. It seems likely that the overexpression of the Ya and Yc subunits, rather than increased levels of the pi-class GST YfYf, is responsible for the acquisition of a drug-resistant phenotype in rat liver preneoplastic nodules and tumours induced by aflatoxin B1.

Aflatoxin B1↗
PubMed1989

The expression of c-myc related to the proliferation and transformation of rat liver-derived epithelial cells.

The expression of c-myc protein was studied in primary cultures of rat hepatocytes and rat liver-derived epithelial cell lines. The levels of the protein were determined by flow cytometry using a monoclonal antibody to the c-myc protein. Freshly isolated hepatocytes from normal adult male Fischer F344 rats had low but detectable levels of the protein which were similar in the different ploidies. Higher levels were detected in immortalised but untransformed rat liver cell lines, and increased expression was observed during passage through the cell cycle. Following in vitro transformation of one of the immortalised epithelial cell lines by ras genes, similar levels of c-myc expression to those present in the untransformed cells was maintained. Transformation by activated aflatoxin B1 (AFB1) resulted in lower levels of expression. The cell cycle related level of expression was also seen in the transformed cells. Similar results to those observed in the in vitro ras transfected liver-derived cell lines were obtained from in vivo AFB1-induced rat hepatoma cell lines. These results demonstrate that continuously dividing rat liver-derived cell lines have higher levels of expression of c-myc protein than non-dividing, freshly isolated hepatocytes, and that there is no further elevation in the levels observed when these cell lines are transformed. In some cases decreased levels can result from malignant transformation.

Animals↗
PubMed1988

Enhanced ethanol-induced changes in disposition and toxic response to dietary aflatoxin B1 due to Sacoglottis gabonensis bark extract, a Nigerian alcoholic beverage additive.

The disposition of, and toxic response, to, dietary aflatoxin B1 (AFB1) was investigated in rats ingesting small doses of Sacoglottis gabonensis bark extract, ethanol, or both, in the drinking-water. Ingestion of ethanol alone or with the bark extract for 8 days resulted in a significant reduction in the level of AFB1 bound to serum albumin, but the level of unbound aflatoxin in the serum was significantly depressed only by concurrent ingestion of ethanol and the bark extract. In contrast, the bark extract alone or with ethanol significantly enhanced AFB1 binding to hepatic DNA. As with serum aflatoxin, concurrent ingestion of ethanol and the extract caused the most pronounced effect, suggesting synergism. All three treatments interfered with both the daily excretion pattern, and level, of aflatoxin in the urine. All three treatments enhanced AFB1-induction of liver gamma-glutamyltranspeptidase activity, suggesting potentiation of toxic response to AFB1. These data suggest that addition of the bark extract to alcoholic beverages may affect the biological response to dietary AFB1.

Aflatoxin B1↗