Liver Monooxygenase Activities Research Articles

HYPOTENSIVE DRUGS EFFECT AND LIVER MONOOXIGENASE FUNCTION IN ARTERIAL HYPERTENSION PATIENTS AFTER ADRENAL HYPERFUNCTION CORRECTION

Hypotensive drug tolerance and liver monooxygenase activity were investigated in 24 refractory arterial hypertension patients before and after surgical suppression of adrenal hyperfunction. Liver monooxygenase activity was studied using antipyrine test. It was found that hypotensive drug tolerance was decreased after one and two side operations on adrenal glands. In parallels halftime of antipyrine elimination was shown to be prolonged by 88.5% in 3 months - 3 years after suppression of adrenal hyperfunction. Our findings suggest that the hypotensive drug tolerance diminution may be the consequence of liver monooxygenase activity reduction. This assumption is in accordance with well known the hypotensive drug metabolism by microsomal liver monooxygenases

Plasmodium berghei (ANKA): Infection induces CYP2A5 and 2E1 while depressing other CYP isoforms in the mouse liver

It has been reported that malaria infection impairs hepatic drug clearance and causes a down-regulation of CYP-mediated monooxygenase activities in rodents and humans. In the present study, we investigated the effects of Plasmodium berghei infection on the activity of liver monooxygenases in female DBA/2 and C57BL/6 mice. In both mouse strains, P. berghei infection decreased activities mediated by CYP1A (EROD: DBA/2 65.3%, C57BL/6 44.7%) and 2B (BROD: DBA/2 64.3%, C57BL/6 49.8%) subfamily isoforms and increased activities mediated by 2A5 (COH: DBA/2 182.4%, C57BL/6 148.5%) and 2E1 (PNPH: DBA/2 177.8%, C57BL/6 128.5%) isoforms as compared to non-infected controls. Since malaria infection also produced an increase in ALT (273.1%) and AST (354.1%) activities in the blood serum, our findings are consistent with the view that CYP2A5 activity is induced by liver injury. An almost generalized depression of CYP-mediated activities has been found with numerous infections and inflammatory stimuli but an induction of CYP2A5 had been previously noted only in some viral hepatitis and trematode (liver fluke) infections.

Toxicological evaluation of an ethanolic extract from Chiococca alba roots

The roots of Chiococca alba have been employed to treat rheumatic disorders and for other therapeutic purposes in Brazil and elsewhere. This study was undertaken to evaluate the toxicological properties of an ethanolic extract from Chiococca alba roots (EE), including mutagenicity in the Salmonella assay and acute and subacute toxicity to mice. Single oral doses of EE caused hypoactivity, but no deaths were noted up to the highest dose tested (2000 mg/kg). EE (500 mg/kg p.o.) reduced mouse locomotion in the open field test. EE was markedly more toxic when given by intraperitoneal (i.p.) and subcutaneous (s.c.) routes. Acute approximate lethal doses (ALD) were 125 mg/kg (males) and 250 mg/kg (females) and 250 mg/kg (both sexes) by i.p. and s.c. routes, respectively. Deaths after single doses were preceded by hypoactivity, ataxia and lethargy. Repeated administration of EE by gavage for 14 days caused no deaths. Activity of liver monooxygenases (pentoxy- and ethoxyresorufin- O-dealkylases) was not altered by repeated treatment with EE (2000 mg/kg/day p.o.). Administration of EE by the i.p. route for 14 days decreased weight gain and caused anemia, neutrophilia and deaths. The no-observed-adverse-effect level (NOAEL) for subacute treatment by the i.p. route was as low as 15.6 mg of EE/kg body weight (wt)/day. EE was not mutagenic in the Salmonella/microsome assay with TA100, TA98, TA97a and TA1535 strains. In summary, EE was not mutagenic and presented a low acute and subacute toxicity by the oral route. Toxicities by parenteral routes, however, were more pronounced.

HEPATOPROTECTOR PROPERTIES OF ERYXIN IN ANIMALS WITH ACUTE DRUG-INDUCED HEPATITIS MODEL

A considerable incidence of side effects caused by drug toxicity and the high lethal outcome of such cases make drug-induced hepatitis an important current problem [1]. Prophylaxis and elimination of liver disorders developed in the course of drug administration can be provided by widely used hepatoprotectors [2 – 4]. Unfortunately, the assortment of modern hepatoprotectors is very restricted [5]. In recent years, public health institutions of the Republic of Uzbekistan widely use the domestic drug eryxin (eriksin) developed at the Institute of the Chemistry of Plant Substances (Academy of Sciences of the Republic of Uzbekistan, Tashkent). This drug represents a highly purified, deprotonated 1% aqueous hydrolysate prepared from the biomass of snakes of the Eryx genus (sand boas). The parent substance contains a complex of biologically active low-molecular-weight compounds, peptides, free amino acids, trace elements (Ca, Mg, K, Fe, S), compounds containing SH groups, etc. [6]. Eryxin exhibits no antigen properties and is administered in the form of intravenous injections in a dose of 1–2m l (1 –2 ampules) per day or via dropper in a dose of 2 – 3 ampules dissolved in 250 ml of a 5% glucose solution or isotonic NaCl solution. Eryxin is administered in cases of immunodeficient states, chronic inflammatory disorders, rheumatological diseases, tuberculosis, brucellosis, acute obstructive or chronic bronchitis, dermatosclerosis, and for the treatment of neoplasms [6]. It should be noted that pathogenesis of acute drug-induced hepatitis always includes inflammatory-dystrophic and necrotic phenomena, with a monooxygenase system (representing predominantly the genetically determined isoforms of cytochrome P-450 [1, 7, 8]) involved in the biotransformation of xenobiotics [9, 10]. Taking this into account, investigation into the hepatoprotector properties of eryxin is a promising direction of research. In this context, we aimed at a comparative study of the effects of eryxin and legalon on the activity of liver monooxygenases and some biochemical characteristics of blood plasma in experimental animals with model acute drug-induced hepatitis. We selected legalon as the reference drug because this preparation possesses pronounced hepatoprotector activity and is widely used in hepatology for the treatment of both acute and chronic hepatitis of various genesis [2, 8, 10].

Effect of immobilization, cold and cold-restraint stress on liver monooxygenase activity and lipid peroxidation of influenza virus-infected mice.

The present study provides a direct experimental evidence that the combination of influenza A/Aichi/2/68 (H3N2) infection with different models of "oxidative stress", such as immobilization, cold and cold-restraint, is associated with graduated oxidative disturbances in the liver of mice, despite the absence of virus and inflammation in this tissue. It was found that experimental influenza virus infection is accompanied with a significant increase of lipid peroxidation products, a decrease of natural antioxidants (vitamin E, glutathione) and cytochrome P-450, an inhibition of cytochrome c reductase and liver monooxygenases (analgin- N-demethylase and amidopyrine- N-demethylase). Immobilization and cold stress, applied separately or in combination (cold-restraint), did not influence significantly any of the analysed parameters compared to those of the control group of non-infected mice. Preliminary exposure of mice to immobilization or cold stress and subsequent inoculation of influenza virus resulted in a significant increase of lipid peroxidation products and a significant decrease of vitamin E and reduced glutathione, compared with levels in control (non-infected) animals. Compared to influenza virus-infected and non-stressed animals, the changes in all these parameters were negligible. Immobilization or cold stress, applied in combination with influenza virus infection, partially prevented the suppressive effect of influenza virus on cytochrome P-450 and liver monooxygenases. A tendency towards normalization of these parameters to the control levels was observed. However, after application of cold-restraint plus influenza virus infection, the level of cytochrome P-450 and activity of cytochrome c reductase stayed markedly lower than in infected and non-stressed animals. The activities of liver monooxygenases were slightly increased compared with those of infected and non-stressed animals, but stayed relatively low compared to control (non-infected) mice. Combination of cold-restraint and influenza virus infection resulted in a greater synergistic increase of lipid peroxidation products and a greater synergistic decrease of vitamin E and reduced glutathione compared to controls, as well as to influenza virus-infected and non-stressed animals.

Effect of long-term multiple nifedipine administration on the antinociceptive activity of acetaminophen.

The influence of long-term nifedipine administration on the antinociceptive activity of acetaminophen on hexobarbital sleeping time and liver monooxygenase and synthetase activities was studied in male albino mice. Nifedipine was administered orally at a dose of 25 mg/kg daily for 14 and 21 days. The nociceptive response was determined by the acetic acid writhing test. There was no significant difference in the antinociceptive effect of acetaminophen after treatment with nifedipine for 14 days. Nifedipine caused enzyme induction, which was demonstrated by shortened hexobarbital sleeping time, enhanced ethylmorphine-N-demethylase (EMND), aniline-4-hydroxylase (AH), ethoxycoumarine-O-deethylase (ECOD), UDP-glucuronyl transferase (UDPGT), glutathione-S-transferase (GST) and NADPH-cytochrome c reductase activity and increased content of cytochrome P450 and cytochrome b5. It is assumed that this effect of nifedipine on acetaminophen analgesia is associated with the changes (acceleration) in acetaminophen metabolism in the liver after repeated administration of the drug.

Mixed-function oxygenases, oxidative stress, and chromosomal damage measured in lesser scaup wintering on the Indiana Harbor Canal.

During the winter of 1993-1994, male lesser scaup (Aythya affinis) were collected on the heavily polluted Indiana Harbor Canal, East Chicago, Indiana, and examined for several bioindicators of chemical exposure. Livers were analyzed for activities of three cytochrome P450-associated monooxygenases and four measures of oxidative stress. Blood and spleen were analyzed by flow cytometry for chromosomal damage. In a concurrent study, scaup tissues were analyzed for organic and inorganic contaminants. Ethoxyresorufin-O-dealkylase (EROD) activity in livers of scaup collected in January 1994 was significantly higher than in livers of scaup collected in March 1994 or in livers of reference birds. Three hepatic monooxygenase activities were each significantly correlated with polycyclic aromatic hydrocarbon (PAH) concentrations in scaup carcasses. Thiobarbituric acid (TBA) activity in scaup livers was positively correlated with iron, boron, and lead concentrations in livers and polychlorinated biphenyl concentrations in carcasses. TBA activity was negatively correlated with protein-bound thiol activity and mercury concentrations in livers. The coefficient of variation of DNA content in scaup blood cells was correlated with PAH concentrations in scaup carcasses. This is the first field study with birds to demonstrate a correlation between liver monooxygenase activity and carcass PAH concentrations and to show a direct correlation between PAH concentrations in tissues and somatic chromosomal damage in blood.

Combined effect of propranolol with nifedipine or with diltiazem on rat liver monooxygenase activities

The effects of two Ca 2+ antagonists nifedipine (NF) and diltiazem (DL) and of the nonselective β-adrenergic blocking agent propranolol (PR) on the hexobarbital (HB) sleeping time and on the activity of some liver drug-metabolizyng enzyme systems in male Wistar rats were studied. Two h after single oral administaration PR (50 mg/kg) did not change HB sleeping time, while NF (50 mg/kg) and DL (30 mg/kg) prolonged it by 171.2 and 99.6%, respectively. Coadmistration of PR with DL or with NF significantly prolonged HB sleep by 240.7 and 129%, respectively. Only NF increased aniline 4-hidroxylase (AH) activity (by 92%) and the total P-450 content (by 24%). PR and NF increased cytochrome b5 content and this effect was also observed with the combinations PR+NF (by 109%) and PR+DL (by 102%). The NADPH cytochrome P-450 reductase activity was significantly decreased by NF and DL and after their combination with PR. The ethymorphine- N-demethylase (EMND) and amidopyrine- N-demethylase (APND) activities were not changed. The effects of PR, NF and DL administrated alone or in combination on liver oxidative metabolism are considered as possible mechanisms of drug interactions.

Determination of processes of lipid peroxidation and liver monooxygenase activity in white mice after treatment with different doses of alpha-tocopheryl-acetate

Determination of processes of lipid peroxidation and liver monooxygenase activity in white mice after treatment with different doses of alpha-tocopheryl-acetate

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 (IC 50) was around 20 μM, whereas a K i of 3 μM 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 IC 50 of 200 and 260 μM. The inhibition was `non competitive' for PROD activity and `mixed' for EROD. The K i of the reactions were respectively 177 and 510 μM. 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.

Multiresponse biomarker evaluation of interactions between methylmercury and Arochlor 1260 in quail

The single and combined effects of methylmercury and Arochlor 1260 were investigated in experimental quail treated chronically with the two compounds at low and high doses. A series of metabolic and biochemical biomarkers were evaluated together with mercury and PCB accumulation to pinpoint the effects of treatment with one or both chemicals. Methylmercury alone was associated with a decrease in serum cholesterol. Less PCBs were accumulated in tissues when Arochlor 1260 was combined with methylmercury than when the former was administered alone. Liver monooxygenase (MFO) activity was depressed 50% more in the presence of methylmercury than with Arochlor 1260 alone. Single or combined treatment with high doses of the two compounds resulted in similar degrees of DNA damage. This approach was found to provide a good picture of the interaction between environmental contaminants.

Activity of liver monooxygenase system in rats with low and high resistance to hypoxia

Rats with low and high resistance to hypoxia are shown to differ in terms of the baseline activity of liver monooxygenases bothin vivo andin vitro. Low-resistance animals are characterized by a significantly higher rate of elimination of antipyrine, hexenal, and nifedipine, as evidenced by shorter half-elimination period and higher urinary concentration of metabolites. The concentration of microsomal cytochromes P-450 and b5 as well as the rates of N-demethylation of amidopyrine, p-hydroxylation of aniline, and hydroxylation of diazepam are considerably higher in rats with low resistance to hypoxia.

PCB levels in bird blood and relationship to MFO responses

A non destructive methods of risk evaluation using blood is proposed for birds. Japanese quail ( Coturnix coturnixjaponica ) were fed different doses of Arochlor 1260 for 25 days to evaluate chemical stress in relation to accumulation, compartmentation and the release of PCBs into blood circulation. Total PCBs were determined in blood and liver. EROD, BROD, PROD, aldrin epoxidase and cytochrome P-450 were measured in the liver microsomal fraction, and the somatic liver index was calculated. In blood and liver, the principal congeners found (153, 138, 180 and 170) were the most persistent ones. Statistically significant correlations were found between liver monooxygenase activity, PCB levels in blood and dose. Evaluation of PCBs in blood can be proposed as a tool to predict induction of liver monooxygenases.

540 Activity of liver monooxygenases in pediatric oncological patients

Liver monooxygenases (LMO) metabolize most antitumor drugs and LMO activity is a factor determining their efficacy. For example, anticancer agents are less active and more toxic in patients (pts) with concomitant hepatic damages which result in inhibition of LMO activity. The question is how many pts have low LMO activity. We examined 146 pediatrie oncological pts without hepatic pathology by determining half life-time of antipyrin (Tl/2 AP). Only 22% pts had high LMO activity, the same as in healthy (Tl/2 AP is 5h and less). 46% pts had moderate LMO activity (Tl/2 AP is 5–10h) and 32%—low LMO activity (Tl/2 AP is more than 10h). Among 36 pts with concomitant hepatic damages the latter group included 63% pts. So about 1/3 of all pts and 2/3 of the pts with hepatic damages cannot achieve optimal effect of chemotherapy regardless of tumor sensitivity. We believe to optimize the drug efficacy LMO inhibited activity should be stimulated to the normal level before chemotherapy and we have already had positive results of the approach.

Liver enzyme activities after multiple administration of nifedipine in mice.

The effect of multiple nifedipine administration on hexobarbital sleeping time, liver monooxygenase and synthetase activities, lipid peroxidation and microsomal membrane fluidity were studied in male albino mice. The drug was administered orally at a dose of 25 mg/kg daily for 14 and 21 days. Nifedipine caused enzyme induction, demonstrated by shortened hexobarbital sleeping time, enhanced ethylmorphine N-demethylase, aniline 4-hydroxylase, ethoxycoumarine O-deethylase, UDP-glucuronyl transferase, glutathione S-transferase and NADPH-cytochrome c reductase activities and increased content of cytochrome P450 and cytochrome b5. This effect persisted until the 7th day after the last dose of nifedipine. There were no changes in lipid peroxidation and fluidity of the microsomal membranes after 14-day nifedipine administration. The increased cytochrome P450 content and drug metabolizing enzyme activities could be not associated with changes in these liver microsomal membrane properties.

Differences in hepatic microsomal cytochrome P-450 isoenzyme induction by pyrazole, chronic ethanol, 3-methylcholanthrene, and phenobarbital in high alcohol sensitivity (HAS) and low alcohol sensitivity (LAS) rats.

High and low alcohol sensitivity (HAS and LAS) rats have been selected for their differences in ethanol-induced sleep time. Liver monooxygenase activities were studied in HAS and LAS rats before and after treatments with known inducers such as chronic ethanol, pyrazole, 3-methylcholanthrene (3-MC) and phenobarbital (PB) to determine whether the selection procedure also selected for differences in the cytochrome P-450 (P-450) inducibility. This previously has been shown with long sleep (LS) and short sleep (SS) mice, which were selected using a similar criterion. 3-MC and PB, in conjunction with chronic ethanol treatment, were used in order to evaluate the interactions of ethanol with these inducers. Prior to treatment, total P-450 content was slightly lower in LAS than in HAS rats. However, both lines displayed the same microsomal monooxygenase activities related to different P-450 isozymes. This was demonstrated by ethoxyresorufin deethylation (EROD) for cytochrome P-450 1A1 (CYP1A1), acetanilide hydroxylation (ACET) for CYP1A2, pentoxyresorufin dealkylation (PROD) for CYP2B, 1-butanol oxidation (BUTAN) and N-nitrosodimethylamine demethylation (NDMA) for CYP2E1. After the different treatments, HAS rats did not differ from LAS rats in their CYP2E1 inducibility. However, pyrazole, PB and 3-MC treatment led to differences in CYP1A and CYP2B monooxygenase activities between the two lines. The enhancement of PROD by pyrazole treatment was less prominent in LAS (1.7-fold of the control value) than in HAS rats (3.8-fold).(ABSTRACT TRUNCATED AT 250 WORDS)

Caloric Restriction Affects Liver Microsomal Monooxygenases Differentially in Aging Male Rats

Caloric restriction (CR) extends life span and retards the onset of physiological changes and pathologies associated with aging, but the underlying mechanisms remain unresolved. This study demonstrates that CR postpones the documented age-related declines in and/or enhances the activity and microsomal concentration of several liver monooxygenases in male rats, i.e., NADPH cytochrome P-450 reductase, total cytochromes P-450. However, the relative concentration of cytochrome P-450b+C did not exhibit statistically significant changes, whereas another isozyme, the male specific P-450h, declined significantly in both ad libitum-fed and CR rats as a function of increasing age. While CR appears to retard age-associated changes in certain liver enzymes, this effect is by no means universal. The hepatic monooxygenases constitute a well-characterized enzyme system in which to examine the perturbation of the aging process by CR.

Inhibition of rat liver monooxygenase activities by 2-methyl-1,4-naphthoquinone (menadione)

In rat liver microsomes, 2-methyl-1,4-naphthoquinone (menadione) inhibits cytochrome P450 (cyt P450)-mediated aniline-p-hydroxylation and aminopyrine-N-demethylation with K i values of 12 and 14.5 μ m, respectively. The inhibitions of aniline-p-hydroxylation and aminopyrine-N-demethylation are mixed uncompetitive-noncompetitive and mixed competitive-noncompetitive, respectively. NADP antagonizes the inhibitory effect of menadione on aniline- p-hydroxylase activity but not that on aminopyrine- N-demethylase activity. Menadione does not give rise to any spectral change of cyt P450, but modifies the type I binding spectrum induced by aminopyrine. In contrast, menadione does not change the type II binding spectrum induced by aniline. These results indicate that menadione may inhibit aniline- p-hydroxylase activity by acting as a substrate for NADPH-cyt P450 reductase in the place of cyt P450 and inhibit aminopyrine- N-demethylase activity by impairing the binding of aminopyrine to cyt P450.

Flavonoids as inhibitors of rat liver monooxygenase activities

Flavanone and six hydroxylated derivatives, and cianidanol and eight ethers and esters thereof, were investigated as inhibitors of cytochrome P-450 mediated reactions in rat liver microsomes. The IC 50 values towards aminopyrine N-demethylation varied over a 20-fold range and were shown to depend on the pattern of hydroxylation (flavanone derivatives) and on lipophilicity (cianidanol derivatives). In the latter case, a bilinear relationship exists, the optimal log P being 2.92. Using selected compounds, IC 50, K m and V max values were determined for aminopyrine N-demethylation, biphenyl 4-hydroxylation, and biphenyl 2-hydroxylation. Depending on the inhibitor and on the activity examined, non-competitive, competitive, or mixed inhibition was seen. Interaction with cytochrome P-450 was also studied spectrally and was always found to result in a modified type II difference spectrum (ligand binding). A dual binding mode is postulated, involving electrostatic and lipophilic interactions.

A correlation between serum mebendazole concentrations and the aminopyrine breath test. Implications in the treatment of hydatid disease.

In 25 patients an [14C]-aminopyrine breath test (ABT) was performed immediately before the oral administration of 1.5-2 g of mebendazole three times daily. The concentration of mebendazole in serum was measured 2 h after each drug intake. A significant correlation was found between the results of ABT and the serum drug concentrations obtained after the second and third intake, as well as the highest concentration value. The ABT was repeated in six patients during a continuous treatment with mebendazole. In all of them this test indicated an increase in 14CO2 production with continued treatment. The results support the view that mebendazole is metabolized by the liver monooxygenase activity and behaves as an enzyme inducer.