Subclinical doses of T-2 toxin impair acquired immune response and liver cytochrome P450 in pigs.

This study was designed to investigate the effect of subclinical doses of T-2 toxin on liver drug-metabolizing enzymes and the immune response. Pigs were offered over a 28-day period either a control diet or diets contaminated with 540, 1324 or 2102microg pure T-2toxin/kg feed. Pigs were immunized with ovalbumin and subsequent humoral and cellular immune responses measured. Monooxygenase and transferase enzyme activities and protein expression were investigated in liver tissue samples. Pigs fed 1324 or 2102microg T-2toxin/kg feed exhibited reduced anti-ovalbumin antibody production without significant alteration to specific lymphocyte proliferation. The livers of pigs exposed to T-2 toxin presented normal cytochrome P450 content, UGT 1A and P450 2B, 2C or 3A protein expression, and glutathione- and UDP glucuronosyl-transferase activities. However, P450 1A related activities (ethoxyresorufin O-deethylation and benzo-(a)-pyrene hydroxylation) were reduced for all pigs given T-2 toxin, with P450 1A protein expression decreased in pigs fed the highest dose. In addition T-2 toxin exposure reduced certain N-demethylase activities. The results of this study confirm the immunotoxic properties of T-2 toxin, in particular toward the humoral immune response. The reduction of monooxygenase activities, even though the liver presented no tissue lesion or lipid peroxidation, suggests possible deleterious interactions of T-2 toxin with these enzymes.

Surface effects on exciton diffusion in non polar ZnO/ZnMgO heterostructures.

The diffusion of excitons injected in ZnO/Zn0.92Mg0.08O quantum well heterostructures grown by metal-organic-vapor-phase-epitaxy on non-polar ZnO substrates is investigated at room temperature. Cathodoluminescence linescans in a field-emission-gun scanning-electron-microscope are performed across cleaved cross-sections. A 55 nm diffusion length is assessed for excitons in bulk ZnMgO. When prepared as small angle bevels using focused ion beam (FIB), the effective diffusion length of excitons is shown to decrease down to 8 nm in the thinner part of the slab. This effect is attributed to non-radiative surface recombinations, with a 7 × 104 cm s-1 recombination velocity estimated at the FIB-machined ZnMgO surface. The strong reduction of the diffusion extent in such thin lamellae usually used for transmission electron microscopy could be use improve the spatial resolution of cathodoluminescence images, often limited by diffusion processes.

Effect of various doses of deoxynivalenol on liver xenobiotic metabolizing enzymes in mice.

DON is one of the major mycotoxic contaminant of cereal grains throughout the world. The purpose of this investigation was to characterize the effects of a range of environmentally relevant doses of DON in mice exposed through a subchronic toxicological assay. Animals received 3 days per week for 4 weeks, 0.014, 0.071, 0.355 or 1.774 mg of toxin/kg b.w. All doses, except 0.014 mg/kg, provoked increases in plasma immunoglobulin A whereas there was no change in plasma biochemical parameters such as alkaline phosphatase, electrolytes or other immunoglobulins. Administration of 0.071 or 0.355 mg/kg doses led to increased liver microsomal pentoxyresorufin depentylase and cytosolic glutathione transferase activities. Examining protein modulation, western blot analyses liver fractions from mice receiving these doses revealed increased levels in both P450 2b, GST alpha and pi isoenzymes without any change in P450 1a expression. A significant competitive inhibition of deoxynivalenol on CDNB conjugation in vitro suggests that the mycotoxin is a putative substrate for glutathione S-transferases. These changes in liver xenobiotic metabolizing enzymes are discussed by considering the structural nature of deoxynivalenol and previous reports on similar effects exerted by other trichothecenes. These results suggest that a subchronic exposure to low doses of deoxynivalenol causes changes in the normal liver metabolism of xenobiotics.

Individual and combined effects of low oral doses of deoxynivalenol and nivalenol in mice.

Deoxynivalenol (DON) and nivalenol (NIV) are toxic Fusarium secondary trichothecene metabolites that often co-occur regularly in cereal grains. These compounds were compared for their toxicity towards C57BL/6 mice on several parameters including alteration in plasma biochemistry, immune system reactivity and hepatic drug metabolism capacity. Mice received individual or combined oral doses of each toxin: 0.071 or 0.355 mg/kg of body weight, administrated three days a week for 4 weeks. Food consumption was altered by the single administration of 0.355 mg/kg of NIV, although no noticeable change of body and organ weights or liver protein contents was detected. NIV administration did cause also significant changes in total CO2 and uric acid concentrations in plasma. Individual toxin exposures led to increases in plasma IgA without no detectable change in the ex vivo production of cytokine by splenocytes. The liver ethoxyresorufin O-deealkylase, pentoxyresorufin O-depenthylase and glutathione S-transferase activities were increased in concert with cytochrome P4501a and P4502b subfamily expression. Administration of combinations of DON and NIV resulted in responses similar to that observed using individual doses of each toxin. However, depending on the ratio of toxin doses and biochemical parameters, some responses could be also additive (plasma IgA and hepatic DCNB conjugation) or synergistic (plasma uric acid).

Differential inhibition of rat hepatic glutathione S-transferase isoenzymes in the course of fascioliasis.

The effects of a subclinical fascioliasis at various stages of its development (at week 3, 6 and 9 after infection by oral administration of 20 metacercariae of Fasciola hepatica) in rats were determined on the activity of enzymes involved in liver metabolism of glutathione and on the subunit pattern of cytosolic glutathione S-transferase. The parasitic pathology was ascertained by clinical observation of the rats and at autopsy. Hepatic microsomal cytochrome P-450 content was significantly decreased in infected rats by week 3 and 6 post-infection. Not correlatively, the catalytic activities of glutathione S-transferase towards 1-chloro-2,4-dinitrobenzene and 1,2-dichloro-4-nitrobenzene were significantly lowered in last stages of the experimental fascioliasis (by week 6 and 9 post-infection). These decreases were correlated to that of subunit 1 as determined by means of high-performance liquid chromatography of cytosolic proteins whereas subunit 6 could also be decreased. Fascioliasis did not alter cytosolic glutathione, glutathione reductase and glutathione peroxidase activities or plasma glutathione S-transferase activity accepting 1-chloro-2,4-dinitrobenzene as the substrate.

Purification of a sheep liver cytochrome P-450 from the P450IIIA gene subfamily. Its contribution to the N-dealkylation of veterinary drugs.

Oral administration of troleandomycin at a dose of 100 mg/kg/day for 6 days to three adult male Lacaune sheep produced a 1.6-fold increase in specific content of liver microsomal cytochrome P-450. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis, microsomal preparations from treated animals exhibited a strong band in the zone of electrophoretic mobility of cytochromes P-450. This band corresponded to a cytochrome P-450 which cross-reacted with rabbit P450IIIA6 antibodies, as demonstrated by immunoblotting. The ovine isozyme was purified to electrophoretic homogeneity by means of successive DEAE cellulose, CM cellulose and hydroxylapatite chromatographic separations. This hemoprotein had an apparent molecular weight of 52 kD as determined by calibrated sodium dodecyl sulfate-polyacrylamide gel electrophoresis and was characterized in terms of spectral data, NH2-terminal amino acid sequence, immunologic and catalytic properties. This study revealed some interspecies differences with the orthologous rabbit isozyme. The contribution of this form to the N-demethylation of erythromycin and of three veterinary drugs: chlorpromazine, chlorpheniramine and bromhexine was demonstrated from inhibition by TAO, from immunoinhibition studies, using polyclonal antibodies raised in rabbit and from the existence of significant correlations between its microsomal level and these N-demethylase activities. In contrast, the results suggest that ovine P450IIIA could not be predominantly involved in the N-dealkylation of benzphetamine, ephedrine, ivermectine or spiramycin.

Inducing effect of oxfendazole on cytochrome P450IA2 in rabbit liver. Consequences on cytochrome P450 dependent monooxygenases.

Male New Zealand rabbits were dosed with either 0.9, 4.5 or 22.5 mg/kg/day of oxfendazole by gastric intubation for 10 days. Oxfendazole administered at the therapeutic dose (4.5 mg/kg) and at the highest dose (22.5 mg/kg) increased 1.54- and 2.36-fold the total liver microsomal cytochrome P450 and more particularly the isoenzyme P450IA2 (95 and 184% increases) as demonstrated by western blotting. Increases in ethoxyresorufin O-deethylation and hydroxylations of benzopyrene and acetanilide occurred in livers of the same animals without any change in N-demethylation of aminopyrine, benzphetamine or erythromycin. Because of the unchanged level of mRNA specific to cytochrome P450IA2, as shown by northern blot analysis of poly mRNA, an enzyme stabilization rather than a transcriptional activation of IA2 genes should be involved in the P450IA2 regulation mechanisms. Oxfendazole bound strongly to cytochrome P450, giving rise to a type II spectrum, and inhibited noncompetitively the ethoxyresorufin O-deethylase and acetanilide hydroxylase activities, this confirmed that oxfendazole interacts only with the P450IA2 family. On the basis of a comparison of the enzymatic activities induced by various imidazole drugs, it was concluded that oxfendazole, like omeprazole and albendazole, behaved as a 3-methylcholanthrene-type inducer. These three benzimidazoles did not all belong to the same category of cytochrome P450 inducers as the antifungal drugs miconazole, clotrimazole and ketoconazole.

Comparative effects of cytokines on constitutive and inducible expression of the gene encoding for the cytochrome P450 3A6 isoenzyme in cultured rabbit hepatocytes: consequences on progesterone 6beta-hydroxylation.

Cultured rabbit hepatocytes were used to compare the relative activities of cytokines to inhibit the constitutive or rifampicin (RIF)-induced expression of the cytochrome P450 3A6 gene (CYP3A6). Human recombinant cytokines tested were interleukin-1beta (IL-1beta) (2 U/mL), interleukin-2 (IL-2) (5,000 U/mL) and interferon-gamma (IFN-gamma) (50 U/mL). Hepatocytes were cultured in the presence or absence of 25 microM RIF for 24 hr, with or without cytokines alone or in combination. All these cytokines inhibited RIF-induced P4503A6 expression without apparent cellular toxicity. By contrast, only IFN-gamma treatment provided a significant decrease (41%) in the constitutive P4503A6 protein level. Moreover, cytokines differed in their ability to repress RIF-dependent transcriptional induction of CYP3A6: IL-1beta and IL-2 were approximately equipotent, causing an almost 40-50% suppression of CYP3A6 mRNA and protein levels, whereas IFN-gamma exerted repressive effects only on P4503A6-related erythromycin N-demethylase activity and inducible protein expression. In fact, although strongly reducing P4503A6 protein content (an approximate 70% decrease), IFN-gamma did not exhibit any influence on CYP3A6 mRNAs with the exception of its association with interleukins. All these results suggest that IL-1beta and IL-2 mainly promote a transcriptional repression mechanism, given the absence of effect of these cytokines on the basal P4503A6 level, whereas IFN-gamma exerts a post-transcriptional suppressive action on both induced and constitutive P4503A6 expression. Consequently, P4503A6-dependent progesterone 6beta-hydroxylase activity also presented a cytokine-specific pattern of inhibition, with a much greater sensitivity than P4503A6 immunoreactive protein to IL-1beta and IL-2 + IFN-gamma treatments. Thus, this study underlines the significant impact of inflammation on steroid metabolism.

Comparison of hepatic and extrahepatic drug-metabolizing enzyme activities in rats given single or multiple challenge infections with Fasciola hepatica.

The activity of drug-metabolizing enzymes was compared in liver, kidneys and lungs of rats given single or repetitive fluke infections. Fascioliasis was induced by oral administration of 20 metacercariae of F. hepatica to rats, either 6, or 12 and 6, or 12, 9 and 6 weeks before sacrifice. In the liver of mono-infected rats, significant reductions (24-67%) were observed in microsomal content of cytochrome P450 and all P450-dependent monooxygenases investigated. Conjugations to glutathione or acetate were lowered by 34-50% in these animals. In multiply infected animals, a majority of specific enzymatic activities were unchanged, while some monooxygenase activities such as aminopyrine demethylation or benzo(a)pyrene hydroxylation were increased by 26-76% in the liver of tri-infected rats. A renal compensatory process occurred in all infected groups, since cytochrome P450, benzphetamine demethylation and glutathione conjugation were significantly increased. By contrast, dealkylation of benzphetamine and pentoxyresorufin were decreased in the lungs of monoinfected rats. The development of parasite resistance would account for the recovery of liver drug metabolizing capabilities in multi-infected animals.

Comparison of hepatic and renal drug-metabolising enzyme activities in sheep given single or two-fold challenge infections with Fasciola hepatica.

The activity of drug-metabolising enzymes was compared in liver and kidneys of adult sheep given single or two-fold fluke infection. Fascioliasis was induced by oral administration of 200 metacercariae of Fasciola hepatica to female sheep either 10 or 20 weeks (mono-infections) or 10 and 20 weeks (bi-infection) before killing. The parasitic pathology was ascertained at autopsy and by clinical observation of animals. In the liver of both mono- and bi-infected animals, significant decreases (P<0.05) (17-44%) were observed in the microsomal content of cytochrome P450 and in the two measured P450-dependent monooxygenase activities, benzphetamine and ethylmorphine N-demethylations. Moreover, Western blot analysis of microsomes demonstrated a decrease in the expression of cytochrome P4503A subfamily correlative with that of its presumed corresponding activity ethylmorphine N-demethylase. By contrast, the conjugation of chloro-dinitrobenzene to glutathione remained unchanged in liver cytosolic fractions prepared from all these animals. In kidneys, a significant decrease (P<0.05) (30%) in microsomal cytochrome P450 level of 10-week mono-infected sheep was observed whereas there was no change in the other groups of animals. The inflammatory origin and the consequences in terms of pathology and animal productivity of the fascioliasis-induced decreases in tissue-oxidative drug metabolism are discussed, particularly in the case of adult sheep suffering repetitive infections.

Ontogenic development of liver progesterone metabolism in female sheep. Contribution of cytochrome P4502B and P4503A subfamilies.

Age-related changes in progesterone hepatic metabolism were measured in Lacaune ewes in the foetal, neonatal (1 and 4 weeks), growing (7 months), pregnant (11 months) and adult (6 years) stages. 6 beta-Hydroxylation and 20 alpha-reduction were found to be the most efficient metabolic process in ovine microsomes. These activities were detected in 3-month-old foetuses and they increased rapidly during the first month of life, in a similar manner to the developmental expression of the cytochrome P4503A subfamily. 16 alpha- and 21-hydroxylation of progesterone were characterized by low, constant turn over in sheep liver microsomes during development. The hepatic ovine P4502B isozyme was purified to electrophoretic homogeneity by means of successive DEAE cellulose, hydroxylapatite and CM cellulose chromatographic separations. This hemoprotein had an apparent molecular weight of 51 kDa and was characterized by spectral data, NH2-terminal amino-acid sequence, immunological and catalytic properties. The relative contribution of this form and of the previously purified ovine P4503A subfamily was investigated in liver progesterone metabolism by immunoinhibition studies using polyclonal antibodies raised in rabbits and from the existence of induction and of significant correlations between microsomal activity and specific P450 content. In sheep liver microsomes, it would appear that cytochrome P4502B is involved in progesterone 21-hydroxylation whereas P4503A participates in the 6 beta- and 16 alpha-hydroxylation and possibly in the reductive conversion of progesterone in its 20 alpha-hydroxy derivative.

Consequences of challenge infections with Fasciola hepatica on rat liver P450-dependent metabolism of sex hormones.

The effect of single or repetitive fluke-infections on rat liver steroid hormone metabolism was studied. Fascioliasis was induced by oral administration of 20 metacercariae of Fasciola hepatica to rats, by week-6 (mono-infected) or 12 and 6 (bi-infected), or 12, 9 and 6 (tri-infected) before killing. Total microsomal cytochrome P450 and P450 isoenzymes were measured spectrophotometrically and by Western-blot analysis, respectively. Progesterone and testosterone metabolism were quantified by normal phase high performance liquid chromatography. In control rats, progesterone and testosterone were mainly converted to 2 alpha- and 16 alpha-hydroxymetabolites. In the liver of mono-infected rats, hepatic cytochrome P450 was significantly decreased by 36-64% whereas the expression of all investigated isoenzymes was decreased by 36-82% with the exception of the unchanged P4502E1. 16 alpha- and 2 alpha-hydroxylations of progesterone and testosterone were significantly decreased by 50-90%, these decreases were correlated with those of P4502B1/2 and P4502C11 isoenzymes, respectively. In bi- and tri-infected rats, steroid hormones were metabolized similarly to control rats. The return of steroid drug metabolizing enzyme activities to control level could be related to the immune response associated to the development of the animal resistance to the parasitic infection.

Dose-related effect of aflatoxin B1 on liver drug metabolizing enzymes in rabbit.

The effects of chronic administration of aflatoxin B1 (AFB1) on liver drug metabolism enzymes were measured in New Zealand rabbits divided into three groups of 5 animals, each receiving over 5 days either arabic gum or AFB1 in arabic gum at a daily oral dose of 0.05 or 0.10 mg/kg. These treatments did not lead to any lethality in any of the treated groups, but the body weight gain was altered. Biochemical exploration of plasma components revealed a dose-dependent hepatotoxicity characterized by cytolysis and cholestasis. At 0.10 mg/kd/day of AFB1, significant decreases were observed in total liver microsomal cytochrome P450, several P450-dependent monooxygenase activities, all individual P450 isoenzymes levels analysed by Western-blotting and glutathione S-transferase activities. By contrast, at 0.05 mg/kg/day of AFB1, even though total cytochrome P450 was decreased by 30%, only P450 1A1 and 3A6 isoenzymes, and aniline hydroxylation, pentoxyresorufin O-depentylation, aminopyrine, erythromycin, ethylmorphine and dimethylnitrosamine N-demethylations were affected. In the same animal group, the only glutathione S-transferase accepting CDNB (1-chloro-2,4-dinitrobenzene) as substrate was decreased by 22%. UDP-glucuronyltransferase accepting p-nitrophenol as substrate was increased in both groups of animals (33-62%). The mechanisms that could contribute to the observed changes in drug metabolizing enzymes are discussed.

Reduced cytochrome P450 and increased heme oxygenase in liver during rabbit aflatoxicosis.

The administration of aflatoxin B1 (AFB1) in New Zealand rabbit for 5 days at a daily oral dose of 0.05 or 0.1 mg/kg decreased microsomal hepatic cytochrome P450 whereas a dose-dependent increase in the reduced microsomal 420 nm absorption occurred. The nature of such an absorption was then investigated. Either in vitro incubation of control microsomal proteins with AFB1 up to 800 microM and NADPH, or primary rabbit hepatocyte cultures exposure to AFB1 up to 30 microM for 24 to 72 h, failed to produce any 420 nm absorbing species, suggesting that the 420 nm absorption observed in vivo was due to an hemoprotein increase. Chemical reductions of microsomal proteins from AFB1-treated rabbits confirmed this hypothesis. Enzyme activity determinations revealed an increase in both microsomal heme oxygenase and NADPH-cytochrome c reductase activities in AFB1 treated rabbits, suggesting that the 420 nm absorption observed in vivo was related to a particular increase in heme oxygenase.

Identification of human and rabbit cytochromes P450 1A2 as major isoforms involved in thiabendazole 5-hydroxylation.

This report characterized one of the major cytochrome P450 isozyme involved in thiabendazole metabolism. This study was undertaken by using both cultured rabbit hepatocytes treated or not with drugs known to specifically induced various cytochromes P450 isoenzymes (i.e., P450 1A1/2 by beta-naphthoflavone, P450 2B4 by phenobarbital, P450 3A6 by rifampicine and P450 4A by clofibrate) and human liver (THLE-5) and bronchial (BEAS-2B) epithelial cells expressing or not the major constitutive human cytochromes P450 (i.e., CYP1A2, 2A6, 2B6, 2C9, 2D6, 2E1 or 3A4). Only hepatocytes exposed to beta-naphthoflavone and clofibrate significantly metabolized thiabendazole to 5-hydroxythiabendazole. Extensive biotransformation of this anthelmintic only occurred in human cells expressing CYP1A2. Moreover, experiments performed on rabbit preparations showed good correlations between thiabendazole 5-hydroxylase activity and both ethoxyresorufin and methoxyresorufin O-dealkylase activities. Thus, CYP1A2 is a major isoenzyme involved in thiabendazole 5-hydroxylation.

In vitro interaction of AFB1 with rabbit liver monooxygenase activities.

The purpose of this study was to determine the influence of aflatoxin B1 (AFB1), incubated in vitro with rabbit liver microsomes, on some cytochrome P450-dependent monooxygenases activities. A strong competitive inhibition of the mycotoxin on aniline hydroxylation was observed. The concentration which provoked a 50% inhibition (IC50) was around 20 microM, whereas a Ki of 3 microM was determined. In contrast, only weak inhibitions of both pentoxyresorufin and ethoxyresorufin O-dealkylases (PROD and EROD) activities were obtained. They were characterized by respective IC50 of 200 and 260 microM. The inhibition was 'non competitive' for PROD activity and 'mixed' for EROD. The Ki of the reactions were respectively 177 and 510 microM. Considering the fact that AFB1 has been previously reported to decrease microsomal hepatic cytochrome P450 expression, the results obtained in this study strengthen the hypothesis that the normal metabolism of xenobiotics by the liver could be altered in AFB1 exposure.

Evidence for cytochrome P4501A2-mediated protein covalent binding of thiabendazole and for its passive intestinal transport: use of human and rabbit derived cells.

Thiabendazole (TBZ), an anthelmintic and fungicide benzimidazole, was recently demonstrated to be extensively metabolized by cytochrome P450 (CYP) 1A2 in man and rabbit, yielding 5-hydroxythiabendazole (5OH-TBZ), the major metabolite furtherly conjugated, and two minor unidentified metabolites (M1 and M2). In this study, exposure of rabbit and human cells to 14C-TBZ was also shown to be associated with the appearance of radioactivity irreversibly bound to proteins. The nature of CYP isoforms involved in this covalent binding was investigated by using cultured rabbit hepatocytes treated or not with various CYP inducers (CYP1A1/2 by beta-naphthoflavone, CYP2B4 by phenobarbital, CYP3A6 by rifampicine, CYP4A by clofibrate) and human liver and bronchial CYP-expressing cells. The covalent binding to proteins was particularly increased in beta-naphthoflavone-treated rabbit cells (2- to 4-fold over control) and human cells expressing CYP1A2 (22- to 42-fold over control). Thus, CYP1A2 is a major isoenzyme involved in the formation of TBZ-derived residues bound to protein. Furthermore, according to the good correlation between covalent binding and M1 or 5OH-TBZ production, TBZ would be firstly metabolized to 5OH-TBZ and subsequently converted to a chemically reactive metabolic intermediate binding to proteins. This metabolic activation could take place preferentially in liver and lung, the main biotransformation organs, rather than in intestines where TBZ was shown to be not metabolized. Moreover, TBZ was rapidly transported by passive diffusion through the human intestinal cells by comparison with the protein-bound residues which were not able to cross the intestinal barrier. Consequently, the absence of toxicity measured in intestines could be related to the low degree of TBZ metabolism and the lack of absorption of protein adducts. Nevertheless, caution is necessary in the use of TBZ concurrently with other drugs able to regulate CYP1A2, particularly in respect to liver and lung tissues, recognised as sites of covalent-binding.

Incidence of experimental ochratoxicosis on hepatic disposition of [3H]tetracycline and chloramphenicol in rats.

[3H]Tetracycline or chloramphenicol were injected i.v. into anaesthetized controls and 12-day ochratoxin A-administered rats. The biliary excretion and hepatic levels of [3H]tetracycline were decreased whereas bile flow did not vary and plasma bioavailability of radioactivity increased in comparison with control rats. Ochratoxicosis induced also lower biliary excretion of glucuronide conjugated form of chloramphenicol without any change in its plasma or liver concentration.

Dose-related increase in liver heme catabolism during rabbit aflatoxicosis.

Aflatoxin B1 (AFB1) has been reported to decrease microsomal hepatic cytochrome P450 (P450) content and increase both total plasma bilirubin concentration and liver heme oxygenase activity. The purposes of this study were to determine whether liver hemoproteins contents and heme catabolizing enzymes were affected by the mycotoxin and whether these alterations were linked to hyperbilirubinemia. Male New Zealand rabbits were divided into three groups of five animals, each receiving for 5 days either arabic gum as vehicle or AFB1 at a daily oral dose of 0.05 or 0.10 mg/kg. These treatments affected neither cytochrome b5 content nor NADPH-cytochrome reductase activity. A linear dose-dependent decrease in cytochrome P450 content and increases in both heme oxygenase and biliverdin reductase activities were observed. Bilirubin UDP-glucuronyltransferase activity was dramatically decreased at both doses, whereas cholestasis occurred only at 0.10 mg/kg. An exponential dose-dependent increase in plasma bilirubin concentration was also observed. Both the simultaneous exponential increase in bilirubinemia associated to a reduced bilirubin UDP-glucuronyltransferase activity and the absence of cholestasis at 0.05 mg/kg, suggested that the hyperbilirubinemia is more probably related to an increased heme catabolism than to an altered bile duct permeability.

Effect of low doses of a trichothecene mycotoxin (diacetoxyscirpenol) on rat gastric glycoproteins: a histochemical study.

A histochemical study was carried out to evaluate the changes occurring in the glycoproteins of the stomach of the rat following short-term treatment with the trichothecene mycotoxin, diacetoxyscirpenol (DAS). Staining with alcian blue methods for detecting complex carbohydrates and with lectin conjugates (Con A, LTA, PNA, SBA and WGA) showed an increased alcianophilia at pH 2.6 and pH 1.0 for various parts of the fundic glands. With respect to lectin staining, DAS intoxication was characterized by enhanced labelling with LTA and SBA in the surface epithelium and in the foveolae, while WGA binding appeared in the lower mucous neck cells. These data suggest that the contents of the mucus-producing cells of the fundic glands of the rat stomach could be affected by low doses of diacetoxyscirpenol even following only 2 days of treatment.