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PubMed1985

Characterization of water-soluble glucuronide and sulphate conjugates of aflatoxin B1. 2. Studies in primary cultures of rat hepatocytes.

Aflatoxin B1 and some of its metabolites were released from water-soluble aflatoxin conjugates isolated from rat primary hepatocyte cultures and hydrolysed by enzymes (beta-glucuronidase and sulphatase), by acid or by a combination of both treatments. The presence of AFB1 in the hydrolysates was detected on TLC plates, or indicated indirectly by the Ames mutagenicity assay. The aflatoxin conjugates were not mutagenic to Salmonella typhimurium strain TA98 in the presence of rat-liver S-9 mix. However, following enzymatic hydrolysis, the chloroform extract of the hydrolysate was highly mutagenic to the bacteria, indicating the presence of mutagenic AFB1. The conjugates AFB1-glucuronide and AFB1-sulphate are therefore produced from AFB1 in primary cultures of rat hepatocytes.

Aflatoxin B1↗
PubMed1988

Modification of protein synthetic components by aflatoxin B1.

Molecular sites of perturbation by the hepatocarcinogen aflatoxin B1 (AFB1) in the protein synthesis initiation complex were assessed using isolated hepatocytes and a cell-free activating system containing microsomes and cytoplasmic ribonucleoprotein complexes (cRPC). Ribosomal proteins showed no detectable modification by the toxin in either system. With hepatocytes, initiation factors demonstrated only slight modification by AFB1. RNAs from both hepatocytes and the cell-free system with microsomes and cRPC were modified, with poly(A)-containing RNA exhibiting at least a 5-fold higher modification than poly(A)-lacking RNA. The poly(A)-lacking RNAs were modified in the order 28S rRNA greater than 18S rRNA greater than 5-6S rRNA greater than 4S tRNA. Guanine was the target base of AFB1, but only 10% of the AFB1-GMP adducts were on guanines located in a poly(G) region. These results suggest that guanine modification in RNAs may be responsible for the observed inhibition of translational initiation by AFB1 to a greater extent than modification of either ribosomal intrinsic or associated proteins.

Aflatoxin B1↗
PubMed1984

Prophage induction by liver microsomal metabolites of aflatoxin B1 in lysogenic Pseudomonas aeruginosa.

Microsomal metabolites of aflatoxin B1 (AFB1) causing induction of prophage in lysogenic strain of Pseudomonas aeruginosa SM was studied. Reduction of culture turbidity was determined at various concentrations of toxin. The effect of the toxin was also studied on deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and protein synthesis. AFB1 at the concentration of 50 micrograms/ml reduced initial turbidity to approximately 90% in 4 h. DNA synthesis stopped completely in the first hour but reappeared due to induction of the temperate phage. Soon after induction both RNA and protein synthesis continued but later little or no net synthesis of these macromolecules occurred. Plaque forming units (pfu) were increased approximately 90 times at 2 h as compared to the control. Testing of the effect of AFB1 on the non-lysogenic, sensitive strain demonstrated that although there was no significant decrease in culture turbidity at 50 micrograms/ml concentration of AFB1, DNA synthesis stopped completely within 1 h, while RNA and protein synthesis were increasing throughout the test interval. It has been concluded that the liver microsomal fraction of AFB1 caused induction of prophage in lysogenic cells and inhibited DNA synthesis significantly in non-lysogenic cells.

Aflatoxin B1↗
PubMed1979

Extraction, cleanup, and quantitative determination of aflatoxins B1 ANd M1 in beef liver.

A method for the determination of aflatoxin B1 in eggs was applicable for aflatoxin B1 in liver, but ineffective for aflatoxin M1 in liver because of poor recovery of added aflatoxin and interferences in thin layer chromatography. The method was modified by the addition of citric acid to the extracting solvent and ammonium sulfate to the extract solution for removing protein. The elution system for silica gel column cleanup was also changed by substituting methanol for acetone, and adding a step for confirmation of aflatoxin M1 identity. The method has been used successfully for survey and research on aflatoxin residues in animal tissues.

Aflatoxins↗
PubMed1985

Studies on the detoxication of microsomally-activated aflatoxin B1 by glutathione and glutathione transferases in vitro.

Aflatoxin B1 (AFB1)-8,9-oxide, the proposed ultimate carcinogen is conjugated enzymically with glutathione (GSH) to give 8-(S-glutathionyl)-9-hydroxy-8,9-dihydro AFB1 (AFB1-SG). The GSH conjugate isolated from rat bile was shown, on the basis of 1H n.m.r. to be identical to AFB1-SG. Of the seven soluble rat liver GSH transferases tested, namely GSH transferases 1-1, 1-2, 2-2, 3-3, 3-4, 4-4 and 5-5 (see reference 1 for the new system of nomenclature), only the first three were active with microsomally generated AFB1-8,9-oxide, their rates of conjugation being 1.1, 0.61 and 0.64 nmol/min/mg enzyme, respectively. AFB1-SG is a thioacetal, but it was not formed from the incubation of the hemiacetal, AFB1-8,9-dihydrodiol, with GSH or GSH plus GSH transferase 1-1 plus 1-2. The covalent binding of in vitro microsomally activated AFB1 to DNA and the formation of AFB1-SG were linearly related to AFB1 concentration in the range of 0.2-2 micrograms/ml. DNA binding was decreased by 38% by the competing formation of AFB1-SG throughout this range of concentrations. These results are in accord with the observation of Scott Appleton et al. (Cancer Res., 42, 3659-3662) that, in the rat in vivo, there is no evident threshold for the binding of AFB1 to DNA. These findings are also consistent with the further observation, reported in this paper that GSH and GSH transferases have no effect on the mutagenicity of microsomally activated AFB1 to Salmonella typhimurium TA 100.

Aflatoxin B1↗
PubMed1992

Modulation of aflatoxin B1 biotransformation in rabbit pulmonary and hepatic microsomes.

Aflatoxin B1 (AFB1) is a carcinogenic mycotoxin that requires activation to the corresponding 8,9-epoxide for activity. In addition to being present in foodstuffs, AFB1 can contaminate respirable grain dusts and thus the respiratory system is a potential target for carcinogenesis. In the present study, we have investigated the role of polycyclic aromatic hydrocarbon-inducible forms of cytochrome P-450 in the pulmonary and hepatic microsomal activation ([3H]AFB1-DNA binding) and detoxification ([3H]AFM1 and [3H]AFQ1 formation) of [3H]AFB1. In rabbit lung microsomes, the apparent Vmax for [3H]AFM1 formation was increased significantly when values were expressed per mg microsomal protein or per nmol P-450 present. In liver microsomes, the apparent Vmax for DNA binding and [3H]AFM1 formation were increased by beta-naphthoflavone (BNF) treatment (to 2.3 and 3.3 times control, respectively) when expressed per mg protein, but when expressed per nmol P-450, only AFM1 formation was significantly increased. The apparent Km values for both these reactions were unaffected. The apparent Vmax for [3H]AFQ1 formation was not affected by BNF treatment, but the apparent Km was increased to 4.5 times control. Boiling of microsomes or omitting the NADPH-generating system decreased DNA binding, AFM1 formation and AFQ1 formation by 89-97%, while addition of 1.0 mM SKF-525A inhibited these reactions by 46-57%. Addition of 1.0 mM alpha-naphthoflavone (ANF) had no effect on the biotransformation of [3H]AFB1 in lung microsomes of control rabbits, but significantly decreased AFM1 formation (by 31%) in lung microsomes from BNF-treated animals (other reactions were unaffected). In liver microsomes from BNF treated rabbits, 1.0 mM ANF inhibited DNA binding of [3H]AFB1 by 68%, while there was no effect in control microsomes. ANF significantly inhibited AFM1 formation in liver microsomes from both control and BNF-treated animals (by 87-97% and 67-78% at 1.0 mM and 2.0 microM, respectively), but had no effect on AFQ1 formation in liver microsomes from animals in either treatment group. These results indicate an important role for the 1A subclass of P-450 isozymes in the biotransformation of AFB1 to AFM1 in rabbit lung and liver, and a minor role in AFB1 activation in liver.

Aflatoxin B1↗
PubMed1987

Metabolic basis for the protective effect of the antioxidant ethoxyquin on aflatoxin B1 hepatocarcinogenesis in the rat.

The effect of dietary administration of 0.5% ethoxyquin (EQ) on the in vivo induction of enzymes and effect on aflatoxin B1 (AFB1)-DNA binding in liver and the consequent in vitro metabolism of AFB1 by male Fischer F344 rat liver-derived fractions have been examined. EQ increased microsomal cytochrome P-450s, in particular those isozymes classed as phenobarbital inducible, and the in vitro rate of metabolism of AFB1. The formation of the presumed detoxified metabolites, aflatoxins M1 and Q1, was enhanced to a greater extent than was the formation of the active metabolite, aflatoxin B1-8,9 epoxide (assessed by the level of aflatoxin B1-8,9-dihydrodiol). Prolonged feeding with EQ was accompanied eventually by a reduction in the initially elevated cytochrome P-450 content, but this was not reflected in any significant decrease in the rate of AFB1 metabolism in vitro. EQ increased the glutathione S-transferase activity of the liver cytosol fractions as assessed with the model substrate 1-chloro-2,4-dinitrobenzene. The capacity of these fractions specifically to catalyze the conjugation of AFB1 with glutathione was induced to a far greater extent than was the conjugation of 1-chloro-2,4-dinitrobenzene. gamma-Glutamyl transpeptidase was induced in the periportal areas of the liver lobule. Reduced in vivo binding of [3H]AFB1 to DNA of liver and kidney was found to result from EQ treatment. It is concluded that the reduced hepatocarcinogenesis which results from feeding EQ simultaneously with AFB1 is due to the reduction in DNA-adduct formation which in turn is due at least in part to increased detoxifying metabolism in the microsomal, cytosolic, and plasma membrane compartments of the liver cells.

Aflatoxin B1↗
PubMed2000

Aflatoxin B1 residues in eggs of laying hens fed a diet containing different levels of the mycotoxin.

The present study was carried out to evaluate the excretion of aflatoxin B1 residues in eggs of young laying hens fed aflatoxin B1-contaminated rations for 8 weeks. To this end, 96 twenty-week-old hens were randomly distributed into four experimental groups (24 birds per group) and given rations containing either 0 (controls), 100 micrograms, 300 micrograms or 500 micrograms aflatoxin B1/kg feed. Egg aflatoxin B1 residues were determined by thin layer chromatography; two samples per treatment per week were used for analysis. Egg production and average egg weights were not affected (p < 0.05) in the groups receiving aflatoxin B1-contaminated rations. Residues of aflatoxin B1 were detected only in the eggs of hens given 500 micrograms/kg feed, at levels that ranged from 0.05 to 0.16 microgram/kg (average: 0.10 microgram/kg). The results indicate that the feed to eggs aflatoxin B1 transmission ratio was approximately 5000:1, emphasizing the importance of controlling aflatoxin levels in rations for laying hens.

Aflatoxin B1↗
PubMed1980

Hormonal influences on chemical carcinogenesis: studies with the aflatoxin B1 hepatocarcinoma model in the rat.

The role of adrenocorticotropin, cortisol, and corticosterone on chemical carcinogenesis was investigated using the rat aflatoxin B1 hepatocarcinoma model. The animals were divided into untreated controls and various experimental groups receiving the carcinogen alone or the carcinogen with a hormone. Animals lost during the treatment period died mostly of massive hepatic necrosis. The results following 65 weeks of observation show that: (1) hormones decrease the toxicity of aflatoxin B1; (2) adrenocorticotropin possibly exerts its influence on aflatoxin B1 hepatocarcinogenesis through adrenal stimulation, and (3) in aflatoxin B1-adrenocorticotropin treated animals, hepatocellular carcinoma, cholangiocarcinoma, and malignant lymphoma may be observed.

Adenoma, Bile Duct↗
PubMed2004

Natural occurrence of moulds and aflatoxin B1 in melon seeds from markets in Nigeria.

Shelled melon seeds (Colocynthis citrullus L.) were purchased from markets in randomly selected villages and towns in three states in each of the rain forest (Ogun, Oyo and Osun) and Northern guinea savanna (Kaduna, Niger and Bauchi) zones of Nigeria. The seed samples were analysed for incidence of visibly diseased seeds, moisture content, moulds and aflatoxin B1 contamination. The incidence of diseased seeds ranged from 6.4% to 50.4% in the forest, and 4.3% to 34.3% in the savanna, and the moisture content was 5.6% to 12.6% and 4.5% to 10.3%, respectively. Mould evaluation revealed that Aspergillus was the most frequent genus, followed by Penicillium, Botryodiplodia, Cladosporium and Rhizopus in decreasing sequential order. Aspergillus flavus had the highest individual count in melon seed from both zones. Aflatoxin B1 was detected at levels above 5 microg/kg in 32.2% of samples, while only 3.5% of the samples contained the toxin above the 20 microg/kg Nigerian tolerance level in food. The percentage of samples contaminated with aflatoxin B1 was statistically comparable for the pooled data of villages and towns. The median level of aflatoxin B1 was less than 5 microg/kg in the seed samples, while the mean aflatoxin B1 levels was 14.1 microg/kg in the forest and 13.0 microg/kg in the savanna samples.

Aflatoxin B1↗
PubMedDate not supplied

Determination of aflatoxin B1 levels in peanut butter using an immunoaffinity column clean-up procedure: inter-laboratory study.

Ten United Kingdom laboratories participated in an evaluation of an immunoaffinity column sample preparation procedure used to prepare aflatoxin B1 containing extracts obtained from peanut butters contaminated by aflatoxins. Each laboratory was sent seven randomly numbered samples of roasted peanut butter which included two sets of undisclosed triplicates. These two peanut butters were naturally contaminated with aflatoxin B1 at levels of about 12 and 35 micrograms/kg. The other sample was a nominal blank peanut butter containing approximately 2 micrograms/kg of aflatoxin B1 which was also employed by participants for recovery experiments. Participating laboratories were instructed to follow a protocol regarding the use of the immunoaffinity columns for extract preparation, but were allowed a free choice of instrumental technique for quantification of aflatoxin levels. Mean recovery for spikes was 72%. Coefficients of variation for the results from the 10 participants for the two contaminated roasted peanut butters were, respectively, 45% (on a mean of 13.6 micrograms/kg) and 36% (on a mean of 37.2 micrograms/kg).

Aflatoxin B1↗
PubMed1997

ATP-dependent transport of aflatoxin B1 and its glutathione conjugates by the product of the multidrug resistance protein (MRP) gene.

Glutathione-S-transferase-catalyzed conjugation of glutathione (GSH) to aflatoxin B1-8,9-epoxide plays an important role in preventing binding of this ultimate carcinogen to target macromolecules. Once formed, the aflatoxin B1-epoxide-GSH conjugates are actively extruded from the cell by an unidentified ATP-dependent export pump or pumps. Two possible candidates for this GSH conjugate pump are the 190-kDa multidrug resistance protein (MRP) and the 170-kDa P-glycoprotein. Both proteins belong to the ATP-binding cassette superfamily of transmembrane transport proteins and confer resistance to a similar spectrum of natural-product drugs. Using membrane vesicles from MRP-transfected cells, we found that MRP transports GSH conjugates of both the endo-isomers and exo-isomers of aflatoxin B1-8,9-epoxide in an ATP-dependent, osmotically sensitive manner (V(max) = 180 pmol/mg/min, K(m) = 189 nM). Membrane vesicles from P-glycoprotein-overexpressing cells showed very low levels of transport. MRP-mediated transport was inhibited by an MRP-specific monoclonal antibody and by a variety of GSH derivatives and cholestatic steroid glucuronides. ATP-dependent transport of unmodified aflatoxin B1 by MRP-enriched membrane vesicles was low but markedly enhanced in the presence of 5 mM GSH, even though GSH conjugates of aflatoxin B1 were not formed by the vesicles. These data demonstrate that MRP is capable of energy-dependent transport of aflatoxin B1 and its GSH conjugates and suggest a potential protective role for MRP in mammalian chemical carcinogenesis.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

The kinetics of aflatoxin B1 oxidation by human cDNA-expressed and human liver microsomal cytochromes P450 1A2 and 3A4.

The combined presence of CYP1A2 and 3A4, both of which oxidize aflatoxin B1 (AFB1) to the reactive aflatoxin B1-8,9-epoxide (AFBO) and to hydroxylated inactivation products aflatoxin M1 (AFM1) and aflatoxin Q1 (AFQ1), substantially complicates the kinetic analysis of AFB1 oxidation in human liver microsomes. In the present study, we examine the reaction kinetics of AFB1 oxidation in human liver microsomes (HLMs, N = 3) and in human CYP3A4 and CYP1A2 cDNA-expressed lymphoblastoid microsomes for the purpose of identifying the CYP isoform(s) responsible for AFB1 oxidation at low substrate concentrations approaching those potentially encountered in the diet. AFBO formation by cDNA-expressed human CYP1A2 followed Michaelis-Menten kinetics (Km = 41 microM, Vmax = 2.63 nmol/min/nmol P450). Furthermore, the portion of AFBO formed in HLMs which was eliminated by furafylline, a specific mechanism-based inhibitor of CYP1A2, also followed Michaelis-Menten kinetics (Km = 32-47 microM, Vmax = 0.36-0.69 nmol/min/nmol P450). The formation of AFBO (activation product) and AFQ1 (detoxification product) in cDNA-expressed human CYP3A4 microsomes was sigmoidal and consistent with the kinetics of substrate activation. Accordingly, application of a sigmoid Vmax model equivalent to the Hill equation produced excellent fits to the cDNA-expressed CYP3A4 data and also to the data from HLMs pretreated with furafylline to remove CYP1A2. The Hill model predicted that two substrate binding sites are involved in CYP3A4-mediated AFB1 catalysis and that the average affinity of AFB1 for the two sites was 140-180 microM. Vmax values for AFQ1 formation were 10-fold greater than those for AFBO, and total substrate turnover to both was 67 nmol/min/nmol CYP3A4. Using the derived kinetic parameters for CYP1A2 and 3A4 to model the in vitro rates of AFB activation at low substrate concentrations, it was predicted that CYP1A2 contributes to over 95% of AFB activation in human liver microsomes at 0.1 microM AFB. The important role of CYP1A2 in the in vitro activation of AFB at low substrate concentrations was supported by DNA binding studies. AFB1-DNA binding in control HLMs (reflecting the contribution of CYP1A2 and CYP3A4) and furafylline-pretreated microsomes (reflecting the contribution of CYP3A4 only) catalyzed the binding of 1.71 and 0.085 pmol equivalents of AFB1 to DNA, respectively, indicating that CYP1A2 was responsible for 95% of AFB1-DNA adduct formation at 0.133 microM AFB. These results demonstrate that CYP1A2 dominates the activation of AFB in human liver microsomes in vitro at submicromolar concentrations and support the hypothesis that CYP1A2 is the predominant enzyme responsible for AFBO activation in human liver in vivo at the relatively low dietary concentrations encountered in the human diet, even in high AFB exposure regions of the world. However, because the actual concentrations of AFB in liver in vivo following dietary exposures are uncertain, additional studies in exposed human populations are needed. Quantitative data on the relative rates of AFM1 and AFQ1 excretion (potential biomarkers for CYP1A2 and 3A4 activity, respectively) in humans would be useful to validate the actual contributions of these two enzymes to AFB1 oxidation in vivo.

Adult↗
PubMed1990

Intercellular variation in levels of adducts of aflatoxin B1 and G1 in DNA from rat tissues: a quantitative immunocytochemical study.

Adducts between aflatoxin B1 and G1 and DNA have been visualised and quantified in various rat tissues by a sensitive immunocytochemical approach. The quantitative validity of this assay has been examined by comparison with experiments using radioactively labelled aflatoxin. Rats were exposed to single and multiple doses of aflatoxin and a marked intercellular variation in adduct levels was observed in kidney and lung, in contrast to the liver, where binding was more homogeneous. No adducts were detected in the oesophagus, forestomach, colon, spleen or testes (detection limit approximately 300 pg aflatoxin/mg DNA). The DNA adduct data are discussed in relation to the carcinogenicity of aflatoxin B1 and G1.

Aflatoxin B1↗
PubMedDate not supplied

[Various aspects of the effect of nutritional factors on the metabolism and biological action of aflatoxin B1 in the rat liver].

Interrelationships between the quality of nutrition, oxidative hydroxylation of aflatoxin B1 and lipid peroxidation were studied in biomembranes of hepatocyte endoplasmic reticulum of growing male rats of the WAG strain. Activity of the liver microsomal monooxygenase, lipid peroxidation as well as metabolism of aflatoxin B1 were shown to depend on presence of three essential amino acids (lysine, methionine and threonine) and vitamins A, E and C. Deficiency of these compounds altered the aflatoxin metabolism causing formation of highly reactive metabolites, which might accelerate the carcinogenic effect of the xenobiotic. However, formation of free toxic metabolites of aflatoxin was stimulated under conditions of balanced nutrition as a result of which its toxic effect might be increased.

Aflatoxin B1↗
PubMed1979

The influence of vitamin A status on the response of chickens to aflatoxin B1 and changes in liver lipid metabolism associated with aflatoxicosis.

1 A series of experiments were conducted to investigate the effects of dietary retinol status on chickens ingesting aflatoxin B1. The effects of dietary supplementation with biotin and alpha-tocopherol were also examined. 2. Aflatoxin B1 levels greater than 1 mg/kg diet had a detrimental effect on 'liveability', body-weight gain, food intake and food conversion efficiency. When fed for more than 2 weeks aflatoxin increased relative liver weight and liver lipid concentration. These effects were less pronounced with avitaminotic A chickens. 3. A synergistic effect on hydropericardium development was observed between aflatoxin B1 and retinol. This effect was not observed when the dietary level of alpha-tocopherol was increased tenfold. 4. The specific activities of certain hepatic lipogenic and amino acid-metabolizing enzymes were influenced by aflatoxin ingestion. A reduction in lipogenic enzyme activity was observed before a reduction in the activities of amino acid-metabolizing enzymes. 5. Liver fatty acid composition was significantly influenced by aflatoxin B1. The extent of these changes was reduced by the inclusion of additional dietary biotin.

Aflatoxins↗
PubMed1995

Evaluation of the generation of genotoxic and cytotoxic metabolites of benzo[a]pyrene, aflatoxin B1, naphthalene and tamoxifen using human liver microsomes and human lymphocytes.

1. The ability of model stable epoxides and metabolites generated by human liver microsomes from benzo[a]pyrene, aflatoxin B1, naphthalene and tamoxifen to produce cytotoxicity and genotoxicity in human peripheral lymphocytes has been investigated. 2. The stable epoxides 1,1,1 trichloropropene-2,3-oxide (100 microM) and trans stilbene oxide (100 microM) as well as metabolites generated from aflatoxin B1 (30 microM) and naphthalene (100 microM) by an extracellular metabolising system were toxic to isolated resting mononuclear leucocytes (MNLs), whereas glycidol (100 microM), benzo[a]pyrene (100 microM) and tamoxifen (50 microM) were not. 3. The stable epoxides 1,1,1 trichloropropene-2,3-oxide (100 microM) and trans stilbene oxide (100 microM) but not glycidol (100 microM) were toxic to dividing lymphocytes only after a 72-h exposure. Tamoxifen (30 microM), aflatoxin B1 (30 microM) and their metabolites were also toxic to dividing lymphocytes. Benzo[a]pyrene (100 microM) and naphthalene (100 microM) were not toxic either in the absence or presence of the extracellular metabolising system. 4. Benzo[a]pyrene (100 microM) and aflatoxin B1 (30 microM) were directly genotoxic to lymphocytes, this genotoxicity was significantly enhanced by the presence of the extracellular metabolising system. This indicates that both intracellular and extracellular bioactivation of these two compounds can produce genotoxicity. In contrast, naphthalene and tamoxifen were non-genotoxic.

1-Propanol↗
PubMedDate not supplied

Selenium effect on the growth of carcinogenic fungi and cytotoxic action of aflatoxin B1 on lymphocyte culture and on embryonal development of Xenopus laevis.

The authors report the results of investigations on the protective effect of selenium against teratogenic and cytotoxic action of aflatoxin B1 and the inhibitory action of this element on the growth of fungi producing carcinogenic aflatoxins. Sodium selenate inhibited the growth of cultures of such fungi belonging to the class Fungi imperfecti as Aspergillus flavus, Aspergillus fumigatus, Penicillium meleagrinum and Penicillium rougolosum. Added to cell cultures of lymphocytes sodium selenate inhibited the cytotoxic action of aflatoxin B1 evidenced by inhibition of PHA-stimulated blastic transformation of these cells and reduction in the number of mitoses. Sodium selenate added to the medium in the culture of Xenopus laevis larvae poisoned with aflatoxin B1 reduced significantly the early mortality of embryos and counteracted the teratogenic action of aflatoxin B1. This action was observed, however, only in early phase of morulation. The authors discuss the importance of their observations for the studies on the role of bioelements deficiency in the environment for induction of malignant transformation.

Aflatoxins↗