Microsomal Mixed Function Oxidase System Research Articles

Methoxol's Impact on the Hepatic Microsomal Mixed Function Oxidase System Induced by Phenobarbital and Pyrene in Rats

Insecticides like methomyl (Lannate) are commonly used to keep pests at bay in vineyards. The mixed-function oxidase system undergoes dramatic change after being exposed to methomyl. This research set out to determine if methomyl inhibits phenobarbital-induced CYP 2B1, 2B2, and 3A, as well as benzo[a]pyrene-induced CYP 2D6 (CYP 1A1). There were a total of eight groups, each including six adult male rats. Calcium precipitation was used to separate the microsomes. Extinction coefficients were used to quantify the amounts of the electron transport components cytochrome P450, cytochrome B5, and cytochrome c-reductase. Drug metabolizing enzymes were tested for their efficacy. Mixed function oxidase was significantly elevated in rats when exposed to inducers like phenobarbital and benzo[a]pyrene. Inducer-(Phenobarbital, benzop [a] pyrene) pretreated rats given 4mg/kg methomyl had significantly lower levels of electron transport components and drug-metabolizing enzyme activity compared to inducer treatment alone. The enzymes involved in mixed-function oxidation were likewise affected by methomyl's influence on the induction of phenobarbital. The levels of electron transport components and drug metabolizing enzymes in methomyl-pretreated rats treated with benzo[a]pyrene were much lower than in rats treated with benzo[a]pyrene alone. These findings show that phenobarbital and benzo[a]pyrene increased cytochrome P450 isoform susceptibility to methomyl (CYP 2B1, 2B2, 3A; and CYP 1A1) and the induction pattern of some inducers with respect to CYP 450 isoforms are both modified by methomyl

Role of Cytochrome P450 and Oxidative Stress in Alcohol-Induced Liver Injury

Alcohol-induced liver injury is a significant global health problem. The mechanisms by which alcohol causes cell injury are still not clear. Many of the hepatic toxic effects of ethanol have been linked to its metabolism in the liver and shown to correlate with cytochrome P450 2E1 (CYP2E1) levels, lipid peroxidation, and elevated formation of reactive oxygen species (ROS). CYP2E1 is induced under a variety of pathophysiological conditions, by drugs, and by alcohol. The goal of this review is to describe and characterize the liver cytochrome P450 microsomal mixed function oxidase system including the generation of ROS. The review then discusses biochemical and toxicological properties of CYP2E1 and its contribution to ethanol-elevated oxidant stress and liver pathology.

Induction of hepatic microsomal drug-metabolizing enzymes by inhibitors of 5-lipoxygenase (5-LO): studies in rats and 5-LO knockout mice.

The effect of 5-lipoxygenase (5-LO) inhibitors on the hepatic microsomal mixed-function oxidase (MFO) system of rodents was investigated. After establishing the relative in vitro and in vivo potencies of the 3 test compounds, male Crl:CD (SD) BR rats received CJ-11,802 (0, 10, 50, or 200 mg/kg/day), zileuton (0, 10, 60, or 300 mg/kg/day) or ZD2138 (0 or 200 mg/kg/day) once daily by oral gavage for 14 (zileuton and ZD2138) or 30 (CJ-11,802) consecutive days. Controls were given an equivalent volume of 0.5% methylcellulose vehicle. At necropsy, all livers were weighed, and sections from representative animals (control and highest dose for each compound) were utilized to prepare hepatic microsomal fractions, which were assayed for cytochrome P-450 (CYP) content and the activities of cytochrome c reductase (CRed), para-nitroanisole O-demethylase (p-NOD), ethoxyresorufin O-deethylase (EROD), and pentoxyresorufin O-dealkylase (PROD). A dose-related increase in liver weight occurred in rats given CJ-11,802 and zileuton, while animals administered ZD2138 were unaffected. Rats given CJ-11,802 (200 mg/kg/day) and zileuton (300 mg/kg/day) had increases in CYP, EROD, PROD, CRed and p-NOD compared to corresponding controls, while only the latter two activities were elevated in animals administered ZD2138. To determine if induction of the hepatic microsomal MFO system was related to 5-LO inhibition, male DBA wild-type and 5-LO knockout mice were administered either CJ-11,802 (200 mg/kg/day) or vehicle by oral gavage for 14 consecutive days. At necropsy, liver weight, CYP content, and CRed activity were measured and all were increased similarly in the treated wild-type and knockout mice compared to corresponding controls, indicating that induction was not related to inhibiting 5-LO.

Membrane stabilising effects of natural polyphenols and flavonoids from Sempervivum tectorum on hepatic microsomal mixed-function oxidase system in hyperlipidemic rats

The extensive role of the microsomal mixed-function oxidase (MFO) system in the oxidation of endo-and xenobiotics, in the detoxication, in the generation of reactive free radicals and in the decomposition of the end products of lipid peroxides is well documented in the literature. Steatotic liver is a very frequent damage with different etiology. Drug metabolising reactions are suppressed in fatty liver, in which pathologically increased production of reactive oxygen intermediates may lead to the peroxidation of microsomal membrane lipids and to the change of membrane bound enzyme activities because of overwhelmed protective mechanisms. The subnormal activity of the MFO system may diminish the non specific resistance of the organism. Therefore we have studied the effects of natural flavonoids and polyphenolic compounds on the mixed-function oxidases. Antioxidant, O 2 − and OH scavenger properties of Sempervivum tectorum extract (STF1) were proved by EPR spectroscopic and chemiluminometric techniques. Potential bioactive constituents were determined by chromatography (HPLC, TLC) and spectrometric (UV, UV–VIS) methods. In the present study we reflect on the membrane stabilising, antioxidant and lipid metabolism modifying effects of this extract. It was established that activities of NAD(P)H reductase and content of cytochrome P450 were normalised in liver microsomes of hyperlipidemic rats, if the animals were treated with STF1 (2 g/bwkg for 9 days in drinking water parallel with fat-rich diet feeding). Fatty acid composition, examined by HRGLC analysis, was changed beneficially. NADPH induced lipid peroxidation was also decreased in microsomes in in vivo and in vitro experiments. At the same time the STF1 had no significant influence on MFO system in normolipidemic animals and on cytochrome b5 concentration of microsome fractions of hyperlipidemic rats.

The aminopyrine breath test (ABT) in a rat model of incomplete stenosis of the common bile duct

The hepatic cytochrome P-450 microsomal mixed function oxidase system that plays a major role in the metabolism of many endogenous and foreign compounds is one of the several liver functions impaired in total bile duct obstruction. However, no information existed concerning to the function of this system in incomplete bile duct stenosis, as seen in man in chronic pancreatitis, early stages of tumorous lesions of the common bile duct or in primary sclerosing cholangitis, in which the clinical features could be poor for a long time. In the present study, the microsomal mixed-function oxidase activity was tested in rats with incomplete mild stenosis of the common bile duct, by following weekly the aminopyrine breath test up to three weeks of evolution. The bile duct stenosis was evident from the increase of the biliary pressure, upstream dilatation of the bile duct, and ductular proliferation. Thus leaving the conduct intact, this model simulates a compression or constriction of the bile duct at early stages. The results showed a decrease in the peak of the exhalation and a lengthening of the half time of elimination of 14CO 2 from the metabolized 14C-aminopyrine that was injected, which were restored by the third week. This pattern was rather similar to that of serum bilirubin, which after an initial increase then returned to basal values. The study suggested that aminopyrine breath test, considered a measurement of the demethylase activity of the microsomal mixed function oxidase system, may be impaired in the incomplete stenosis of the bile duct. Likewise hepatic adaptive changes could support its recuperation.

The microsomal mixed function oxidase system of amphibians and reptiles: components, activities and induction

This article reviews current research in amphibian and reptilian cytochromes P450, important to the overall understanding of xenobiotic metabolism in the ecosystem and the evolution of P450s. Amphibians and reptilians contain the normal mixed function oxidase system (MFO). In general the MFO content and activities are less than those found in mammals, but only a few of the known activities have been examined in these vertebrate classes. Research to date has focused on two families of cytochromes P450, CYP1 and 2. The isoforms examined catalyze the classic activities but there have been notable absences. The total number of isoforms present and the breadth of substrates metabolized are yet unknown. Induction by foreign compounds (xenobiotics) is lengthier and yields lower levels of induced activity than is typically found in mammals. When these animals are pretreated with 3-methylcholanthrene (3MC) and β-naphthaflavone (BNF), which are known to induce the same isoform in mammals, multiple isoforms are induced with different activities. Phenobarbital-pretreatment in turtles and alligators induces cytochromes P450 and suggestive data indicates induction in the lizard Agama lizard and the newt Pleurodeles waltl. In amphibians and reptiles a CYP2B protein does appear to be present along with constitutive activities associated with the 2 family of cytochromes P450. The markedly different response to classic inducers combined with lower or absent activities alters the view of how amphibians and reptilians respond to xenobiotic challenges.

Spectral analysis and catalytic activities of the microsomal mixed-function oxidase system of the sea anemone (phylum: Cnidaria)

Cnidarians are primarily marine organisms with a wide and diverse habitat worldwide. Previous studies from our laboratory demonstrated the presence of proteins in the molecular mass range of 50–60 KDa that were recognized by several antibodies raised against fish cytochromes P450 of the CYP 1, 2, and 3 families in microsomes prepared from the columnar regions of 5 species of sea anemones (Heffernan et al. Mar Environ Res 1996;42:353–357). Pursuant to those studies we report herein results of spectral analyses, NAD(P)H-oxidoreductase and ethoxyresorufin O-dealkylase (EROD) of sea anemone microsomal fractions. The predominant feature in the difference spectrum of dithionite (DTN)-reduced, CO-liganded anemone microsomes was a peak with λ max of approximately 418 nm, which slowly increased for about 20 min and decreased after about 40 min. A relatively lower amplitude 450 nm peak was attained within 5 min of CO addition and was stable for up to 90 min. The 450 nm peak did not increase concomitant to the decrease in the 418 nm peak suggesting that the latter is not denatured P450. A significantly larger 450 nm peak was attained in CO-difference spectra when DTN was added prior to CO. NADPH-dependent cytochrome c ( P450) reductase of the sea anemones was 1.8–3.9 nmol/min/mg protein, which is at the lower end of the range observed in invertebrates. NADH-cytochrome c reductase was 9–25 nmol/min/mg protein, while the NADH-ferricyanide ( b 5) reductase ranged from 73–232 nmol/min/mg protein. When microsomal EROD activity was measured under conditions in which the reaction was linear with respect to protein concentration, a decrease in fluorescence was typically observed for the initial 15 min of the time course and then increased linearly for up to 90 min; initial velocities were determined from the increasing linear region. NADPH was the preferred cofactor for EROD activity and the NAD(P)H-EROD activity was higher in Anthopleura elegantissima than Anthopleura xanthogrammica. The Bunodosoma cavernata NADPH-EROD activity was barely noted at the detection limit of the assay and NADH-EROD activity was not detected. These results are consistent with a functional P450-dependent MFO system in cnidarians, with characteristics both similar to and unique from other marine invertebrates.

Effect of Dietary Ascorbic Acid on the Hepatic Microsomal Mixed Function Oxidase System in Liver of Chicks Treated with Escherichia coli Lipopolysaccharide

We determined whether dietary ascorbic acid (0.3 or 3 g/kg diet) modulates hepatic microsomal mixed function oxidase (MFO) system and plasma alpha 1 acid glycoprotein (AGP) concentration in chicks treated with Escherichia coli lipopolysaccharide (LPS). Injection of LPS (250 μg/kg body weight every other day) intraperitoneally for 14 days decreased cytochromes P450 and b 5 content and NADPH-cytochrome c reductase activity in hepatic microsomes in male broilers. Content of cytochromes P450 and b 5 was negatively correlated with plasma AGP concentration. Feeding ascorbic acid partly alleviated the reduction of cytochromes P450 and b 5 in males. Plasma AGP concentration also increased with the LPS injection and was partly lowered by feeding ascorbic acid. The results indicate that dietary ascorbic acid modulates the responses of the microsomal MFO system and of plasma AGP concentration against repeated injection of LPS in male broiler chicks.

Studies of the hepatic mitochondrial and microsomal mixed-function oxidase system during Plasmodium yoelii infection and inducer treatment in Swiss albino mice.

Plasmodium yoelii infection resulted in depression of hepatic mitochondrial and microsomal mixed-function oxidase system indices, e.g. cytochrome P-450, cytochrome b5 and phase II detoxification enzyme glutathione-S-transferase, while heam and haemozoin registered a marked increase in Swiss albino mice. Phenobarbitone (inducer) treatment showed induced levels of hepatic mitochondrial and microsomal cytochrome P-450 and glutathione-S-transferase in normal as well as in infected mice. The induced cytochrome P-450 and glutathione-S-transferase activities were similar in normal and infected mice. The findings were further supported by the isoenzymic profile and drug-binding properties of the terminal monoxygenase, cytochrome P-450.

Effect of sulfamethazine on phenobarbital and benzo[a]pyrene induced hepatic microsomal mixed function oxidase system in rats

Administration of sulfamethazine (300 mg/kg, i.p., single dose) to phenobarbital (80 mg/kg, i.p., 3 days) pretreated rats showed significant decrease in microsomal protein, electron transport components and drug metabolizing enzyme activities, compared with phenobarbital administration alone. Induction of mixed function oxidase enzymes due to phenobarbital was not affected by the pretreatment of sulfamethazine. Sulfamethazine administration to benzo[a]-pyrene (20 mg/kg, i.p., 2 days in oil) pretreated rats showed no significant change, but there was a slight decrease in cytochrome P450 and aminopyrine N-demethylase activity, compared with benzo[a]pyrene administration alone. A significant inhibition was observed in aminopyrine N-demethylase activity due to in vitro addition of sulfamethazine (3.5 mM) to microsomal incubations from untreated, sulfamethazine, phenobarbital and benzo[a]pyrene-treated rats. The results indicate that the phenobarbital induced cytochrome P450 is more susceptible to sulfamethazine than benzo[a]pyrene induced cytochrome P450.

Observations on vitamin K deficiency in the fetus and newborn: has nature made a mistake?

The microsomal mixed function oxidase system metabolizes xenobiotics (Phase I) to products that, if not activated and conjugated for excretion (Phase II), are capable of forming conjugates with cellular macromolecules, including DNA, resulting in toxic, mutagenic, or carcinogenic events. Benzo(a)pyrene (BP), a polycyclic aromatic hydrocarbon, is a model carcinogen for this system. Vitamin K1 (phylloquinone) is a regulator of BP metabolism. These studies demonstrate that K1 is capable of increasing Phase I metabolism and decreasing glutathione transferase activity (Phase II) in chick embryo liver; that deprivation of K1 reduces BP/DNA adducts in mouse liver and reduces tumor formation in mice given intraperitoneal BP; and that K1 supplementation increases BP induced tumor formation in mice. However, epidemiologic studies indicate that children of mothers who smoke during pregnancy may not be at increased risk of cancer. It is known that the placentas from these pregnancies exhibit markedly increased levels of arylhydrocarbon hydroxylase induced by the polycyclic aromatic hydrocarbons in tobacco smoke, but there is no corresponding increase in this enzyme activity in the fetus in such pregnancies. We suggest that the low vitamin K level is a secondary protective mechanism for xenobiotics, such as BP, that may escape the primary placental screen. The recently described role of vitamin K-dependent Gla protein as ligands for receptor tyrosine kinases, also establishes K as a link in cell growth and transformation. It is proposed that the small total body pool of K1 in the adult, which is sufficient only to meet continuing needs, and the even smaller pool in the fetus are protective. This protective effect of low K1 levels is particularly important in the presence of the high mitotic rates and rapid cell turnover in the avian embryo and mammalian fetus.

Effects of overfeeding of protein and energy by force feeding on hepatic microsomal mixed function oxidase system in broiler chickens

Two experiments were undertaken to determine the effects of excess intake of protein and energy on hepatic microsomal mixed function oxidase (MFO) system in male broiler chickens. Two levels of protein (100 or 117% of ad libitum feeding) and energy (100 or 114% of ad libitum feeding) intake in factorial arrangements of treatments were used in experiment 1. Chicks (38 days of age) were provided the dietary treatments by tube-feeding for 8 days. In experiment 2, chicks were fed a control diet (23% protein and 3.2 Mcal metabolizable energy/kg diet) or a high protein and high energy (32% protein and 3.4 Mcal metabolizable energy/kg diet) ad libitum for 11 days. Energy intake over ad libitum feeding resulted in a reduction of cytochromes P-450 and b5 content. Excess intake of protein did not overcome the reduction of the cytochromes by overfeeding of energy. Feeding high protein diet with high energy content resulted in a reduction of the MFO system in the liver compared with feeding a control diet in the ad libitum condition. The results suggest that energy intake in broilers is the predominate modifier of hepatic microsomal MFO rather than protein intake under overfeeding conditions.

Development of hepatic microsomal mixed function oxidase system in male broilers fed a high or low protein diet

This experiment was undertaken to determine the changes in the mixed function oxidase system (MFO) in hepatic microsomes of male broiler chicks fed a 15% crude protein (LP) or 23% crude protein (HP) diet at different ages. The cytochromes P-450 and b5 content per unit of microsomal protein increased with age, while those per unit of body weight reached a maximum at 6 weeks of age, regardless of dietary protein levels. The activity of the MFO in chicks fed the HP diet was greater than those in chicks fed the LP diet during the first 9 weeks after hatching. At 4 weeks of age, cytochromes P-450 and 65, and NADPH-cytochrome c reductase were reduced by feeding the HP diet, but not by the LP diet.

Phenobarbital treatment enhances insulin-mediated glucose metabolism and improves lipid metabolism in the diabetic rat

Previous studies with healthy volunteers and non-insulin-dependent diabetic (NIDDM) patients have shown a strong association between overall glucose metabolism and hepatic microsomal enzyme activity. In this study, the effects of 10-day oral administration of phenobarbital (PB), a potent inducer of the hepatic microsomal mixed-function oxidase system, on carbohydrate and lipid metabolism in the basal state and on glucose kinetics during submaximal hyperinsulinemic (5 mU · kg −1 · min −1 insulin) clamps were investigated in nondiabetic rats and in rats made diabetic by the intravenous (IV) administration of either low-dose (40 mg/kg) or high-dose (55 mg/kg) streptozocin (STZ). In control rats receiving PB in drinking water (0.5 mg/mL), serum insulin and triglyceride levels were diminished without any change in glucose and cholesterol concentrations in the fed state. Administration of PB in drinking water (0.25 mg/mL) to both groups of diabetic rats decreased their water intake and serum triglyceride levels in the absence of an effect on glucose, insulin, and cholesterol concentrations in the fed state. However, fasting serum glucose levels and basal glucose turnover rates were lower in both groups of diabetic rats receiving PB. PB treatment increased the heparin-releasable lipoprotein lipase (LPL) activity of epididymal fat in both control and low-dose diabetic groups; this was not assessed in the high-dose diabetic group. Neither peripheral glucose utilization nor hepatic glucose production during submaximal insulin clamps was modified by PB treatment in nondiabetic rats. In contrast, PB administration enhanced insulin-mediated peripheral glucose utilization, as well as suppression of hepatic glucose production, in both low-dose and high-dose diabetic groups. The stimulatory effect of PB on insulin-mediated glucose utilization in low-dose diabetic rats was confirmed by increased incorporation of (3- 3H)glucose into glycogen in the rectus muscle measured at the end of the clamp. In conclusion, (1) PB administration decreased fasting serum glucose levels and augmented insulin-mediated glucose metabolism in insulin-deficient diabetic rats, and (2) the triglyceride-lowering effect of PB in both nondiabetic and diabetic rats may be in part due to increased clearance by adipose tissue LPL.

Liver Microsomal Mixed-Function Oxidases in Response to Dietary n-3 Fatty Acid Levels in Rats

Phenobarbital (PB)-induced activities of the liver microsomal mixed-function oxidase (MFO) system in response to dietary levels of n-3 fatty acids were investigated in rats. The MFO activities were assessed by the contents of cytochromes P-450 and b5, and the activities of NADPH-cytochrome c reductase, aminopyrine N-demethylase and aniline hydroxylase. A linoleic acid (C18:2, n-6; LA) diet (2.0 energy % as LA) and n-3 fatty acid diets (0.3, 1.0, 1.9 or 4.8 energy % as n-3 fatty acids) were fed to rats for 16 days. The activities of MFOs except that of NADPH-cytochrome c reductase increased, as compared with the LA diet, with increasing the dietary n-3 fatty acid level, concomitant with the increase in n-3 fatty acids and decrease in n-6 fatty acids in liver microsomal lipids. The dietary LA over 1.8 energy % up to 13.8% did not increase the activities of PB-induced MFOs. Consequently, dietary n-3 fatty acids further elevated the PB-induced MFO activities effectively. These results suggest a differential response of dietary n-6 and n-3 fatty acids to the PB-induced MFO activities.

Liver microsomal mixed-function oxidases in response to polyunsaturated/saturated and n-6/n-3 fatty acid ratios of dietary lipids in rats.

The effects of various polyunsaturated/saturated (P/S; 0.29-2.74) and n-6/n-3 (0.49-11.21) ratios of dietary fatty acids and of phenobarbital (PB) stimulation on the activity of liver microsomal mixed-function oxidase (MFO) system were studied in rats using a combination of palm oil, safflower oil and fish oil concentrate. When the n-6/n-3 ratio was kept constant (4.6-4.9) without induction by PB, the highest P/S ratio (2.74) tended to increase the basal PB-uninduced MFO activities; while the PB-induced MFO activities were elevated as the dietary P/S ratio increased. This definitely indicates the role of both n-6 and n-3 polyunsaturated fatty acids (PUFAs) in the elevation of MFO activities with and without PB stimulation. Whereas the n-6/n-3 ratio was varied while maintaining a constant P/S ratio (1.3), the PB-induced MFO activities were significantly elevated by decreasing the n-6/n-3 ratio although the MFO activities were not affected without PB stimulation. The MFO activities induced by PB were directly related to the n-3 PUFA content and inversely related to the n-6 PUFA content of the diets with n-6/n-3 ratios less than 4.55. These results obtained herein suggest that there are significant differences in the effects of n-6 and n-3 PUFAs on liver microsomal MFO activities, especially in relation to the induction of MFOs by PB.

Dehydroepiandrosterone pretreatment protects rats against the pro-oxidant and necrogenic effects of carbon tetrachloride

A single intraperitoneal injection of dehydroepiandrosterone (3β-hydroxy-5-androsten-17-one, DHEA) 17 hr before carbon tetrachloride (CCl 4) poisoning protects rats against liver injury induced by the haloalkane. In liver homogenates, both the increase in malondialdehyde production and the formation of fluorescent lipid peroxidation products are significantly reduced. Also, liver microsomes obtained from DHEA-pretreated rats incubated in vitro with CCl 4 are less susceptible to lipid peroxidation than microsomes from normal animals. The release of liver enzymes into the blood is much reduced in DHEA-pretreated rats, confirming a cause-effect relationship between lipid peroxidation and hepatocyte death. Treatment with DHEA inhibits neither glucose-6-phosphate dehydrogenase activity in the cytosol, nor the microsomal mixed function oxidase system (cytochrome P450 content, aminopyrine demethylase and ethoxycoumarine de-ethylase activities). In animals treated with DHEA, the liver content of total glutathione and vitamin E is not modified. These results support the hypothesis that DHEA protects against CCL 4-induced liver injury through its own antioxidant activity, rather than by interfering with the metabolism of the toxin or with the tissue level of primary antioxidants.

Sex-related differences of hepatic microsomal mixed function oxidase system and antibody production in broilers implanted with corticosterone and/or fed ascorbic acid

1. Most of the components of the mixed function oxidase (MFO) in hepatic microsomes were reduced by corticosterone implants, and the degree of the reduction in females and at an older age was greater than those in males and at a younger age. 2. Ascorbic acid (AA) prevented the reduction in the MFO caused by corticosterone implants. 3. The activities of aniline hydroxylase and aminopyrine N-demethylase were enhanced by corticosterone implants regardless of AA supplementation. 4. The activity of NADPH-cytochrome c reductase in male broiler was greater than that in females under normal conditions. 5. Corticosterone implants and dietary AA had less influence on the antibody production, especially to T-cell dependent antigen.

Effect of anti-basic liver protein antibody-induced liver injury on hepatic drug-metabolizing enzymes in C57 BL/6J mice.

We attempted to produce a model mouse with a liver injury resulting from an immunological mechanism in C57BL/6J mice, and the effect of hepatitis on the hepatic microsomal mixed-function oxidase system was studied. An experimental immunological liver injury model was caused by the intravenous injection of an anti-basic liver protein (BLP) antibody in mice which had been previously immunized with normal rabbit IgG (RGG) and complete Freund's adjuvant. C57BL/6J strain mice showed the highest susceptibility to the immunological liver injury. Typical histopathological changes in the liver included submassive hepatocellular necrosis and infiltration of lymphocytes into the portal tract and sinusoid area in a necrotic lesion. The liver injury in this model was markedly inhibited by the administration of prednisolone (20 mg/kg, p.o.), cyclophosphamide (15 mg/kg, i.p.), levamisole (10 mg/kg, p.o.), glycyrrhizin (50 mg/kg, i.p.) and cepharanthine (10 mg/kg, i.p.), which act on the immune system. Twenty-four hours after the injection of anti-BLP antibody, the activities of aminopyrine N-demethylase, aniline hydroxylase and NADPH-cytochrome c reductase and the content of cytochrome P-450 were mostly reduced, whereas cytochrome b5 and NADH-ferricyanide reductase were not. These results suggest that the experimental liver injury model in C57BL/6J mice is useful as a model of liver injury model, and its hepatitis was shown to inhibit the cytochrome P-450-dependent biotransformation of drugs in the mouse.

The effects of direct and microsomal activated aflatoxin B 1 on chicken peritoneal macrophages in vitro

Sephadex-elicited peritoneal exudate cells were cultured on glass coverslips in order to determine the effects of aflatoxin B 1 (AFB 1) on chicken macrophages. Adherent macrophage monolayers were exposed for 1 h to 5, 10, and 20 μg ml −1 of AFB 1, directly or to 0.01, 0.1, 0.5, 1, and 5 μg ml −1 of AFB 1 in the presence of a chicken microsomal mixed function oxidase system (MFO). After exposure, the macrophage cultures were washed and allowed to recover for 2 h in fresh culture medium. Parameters measured at 2 h post recovery period were the substrate adherence potential, morphological alterations, phagocytic ability, and number of sheep red blood cells (SRBC) internalized per phagocytic macrophage. Direct in vitro exposure to AFB 1 resulted in a dose-dependent decrease in macrophage adherence potential, and an increase in cell damage as determined by nuclear disintegration and cytoplasmic blebbing, but no detrimental effects were observed on percent phagocytic cells or the number of internalized SRBC. However, significant reductions in adherence potential, increased morphological alterations, and reduced phagocytosis and internalization of SRBC were observed when MFOs were added to cultures treated with much lower doses of AFB 1. Addition of piperonyl butoxide (a P-450 inhibitor) abrogated AFB 1-MFO induced alterations. This study suggests that microsomal activated AFB 1 causes significant alterations in chicken macrophage functions.