[Inhibitory effect of ortho-aminoazotoluene on diethylnirtosamine hepatocarcinogenesis in suckling mice. Phenomenon and possible mechanism].

The modifying effect of the one compound on carcinogenicity of the other in the combined application is attributed usually to some changes in the carcinogen metabolism, i.e. its activation or inactivation. In this paper, when used separately, diethylnitrosamine (DENA) induced 4-6 times more neoplastic lesions in the liver of suckling mice than ortho-aminoazotoluene (OAT) did. However, after combined treatment with both carcinogens the total number of hepatic lesions was significantly lower than that in mice treated with DENA only. Similar effect was observed when OAT was administered 3 days before or 3 days after DENA injection. The observed protective effect is not mediated at metabolic level, because OAT has no effect on metabolism of DENA in mouse liver. Our findings can be unequivocally explained by the competition of the carcinogens for target protein molecules, presumably transcription factors, participating in hepatocyte differentiation, which differently interact with and are diversely impaired by different compounds.

[Age-related changes in protein and lipid oxidation in the liver of prematurely aging rats OXYS]. / Vozrastnye izmeneniia okislennosti belkov i lipidov v pecheni prezhdevremenno stareiushchikh krys OXYS.

Age-dependent variations in products of lipid peroxidation products (LPO) and oxidative damage of proteins have been studied in the liver mitochondria and microsomes of premature aging OXYS rats. Characteristics of oxidative processes in OXYS rats were compared with parameters in Wistar rats. Changes in lipid peroxidation products content and oxidative damage of proteins in rat liver mitochondria and microsomes of both strains rats were nonlinear and had opposite direction during the first year of life. The level of protein oxidative damage in OXYS rat liver mitochondria and cytosol was higher than in Wistar at 12 months. The content of primary and end lipid peroxidation products in OXYS rat liver microsomes was significantly decreased in 12 months, but content of conjugated dienes was increased in mitochondria.

[Bilirubin as an endogenous intermediary in the activation of CYP1A1 expression upon exposure to ultrasound]. / Bilirubin kak éndogennyi posrednik v aktivatsii ékspressii CYP1A1 pod deistviem ul'trazvuka.

The induction of cytochrome P4501A1 (CYP1A1) enzyme activity reflects the increased ligand-dependent transcriptional activity of the cognate CYP1A1 gene. The list of ligands includes various xenobotics such as polycyclic and halogenated aromatic hydrocarbons. Until recently, similar role for endogenous compounds was unknown. In the present study the ability of the endogenous heme metabolite, bilirubin, to regulate CYP1A1 activity was examined. The following parameters were investigated: expression of CYP1A1 in rat liver at a level mRNA, protein and functional activity under at the experimental rising of blood bilirubin level. The influence of local ultrasound contact treatment of rats hepatic area in vivo (the intensity 0.4 W/cm2 and duration time of 10 minutes) on blood unconjugated bilirubin concentration and parameters of CYP1A1 transcriptional activity was also investigated. The ultrasound contact action on rat hepatic are increased blood unconjugated bilirubin concentration. The rise of bilirubin levels of in rat blood after intravenous administration of bilirubin as well as after ultrasound treatment was accompanied by increased mRNA CYP1A1, protein and functional activity of CYP1A1. The comparison of these data with that of time-dependent changes of parameters of CYP1A1 transcriptional activity under ultrasound action and experimental rising of blood bilirubin level suggest that induces CYP1A1 and may be an intermediate in the activation of CYP1A1 expression under ultrasound action.

[The effect of low-intensity physical therapeutic factors on the microsomal oxidative systems of the liver in an experiment]. / Vliianie nizkointensivnykh fizicheskikh lechebnykh faktorov na mikrosomal'nye okislitel'nye sistemy pecheni v éksperimente.

The authors' rat experiments have shown that inhibition of pro-oxidant reactions in hepatocyte microsomal fraction in response to hepatic exposure to low-intensive IR-laser radiation and low-intensity ultrasound combines with multidirectional action of these factors on the basic enzymes of the other oxidant system of hepatocyte microsomes--cytochrome P-450-dependent monooxigenase system.

[Change in activity of microsomal cytochrome P-450-dependent monooxygenases from rat liver exposed to chronic low doses of radiation]. / Izmenenie aktivnosti mikrosomal'nykh tsitokhrom-P-450-zavisimykh monoksigenaz pecheni krys pod vliianiem khonicheskogo vozdeistviia malykh doz radiatsii.

The activity changes of cytochrome P-450-dependent monooxygenases of hepatic microsomal fraction were studied in, experimental animals after prolonged application (1 month) of low radiation doses (0.258 mkl/kg). The obtained results show the increase in catalytic activities of main forms of cytochrome P-450, participating in steroid hydroxylation, as well as the decrease in total content of cytochrome P-450 in hepatic microsomal fraction and the lowering of its demethylase activity.

[Oxidative phosphorylation activity, F0F1-ATPase and level of liver mitochondrial cytochromes in rats with congenitally increased ability for free radical formation]. / Aktivnost' okislitel'nogo fosforilirovaniia, F0F1-ATPazy i soderzhanie tsitokhromov mitokhondrii pecheni krys s vrozhdennym povysheniem sposobnosti radikaloobrazovaniia.

The rates of oxygen consumption in liver mitochondria of strain S rats (2-3- and 10-12-months-old) with inherited free radical hyperproduction during oxidation of three types of substrates (glutamate+maleate, succinate+rotenone and ascorbate+TMPD) as well as cytochrome a level in the respiratory chain are lowered in comparison with Wistar controls. In liver mitochondria of 10-12-months-old rats these changes are more pronounced and manifest themselves as decreased ADP/O, phosphorylation rates and F0F1-ATPase activity. The phosphorylation potential, ATP content and adenine nucleotide pool in rat liver are also reduced. The experimental results give a better insight into the pathogenetic mechanisms of morbid states (e.g., degenerative diseases) in human beings and shed additional light on the origin of short lifespan and premature in strain S rats.

[Induction of cytochrome P-450 1A1 in rat liver by ultrasound]. / Induktsiia tsitokhorma P-450 1A1 v pecheni krys ultrazvukom.

Rat liver monooxygenase activities, such as androstenedione (AD)-hydroxylase, pentoxyresorufin (PR)- and ethoxyresorufin (ER)-O-deethylases have been studied under contact application of ultrasound (US). In the livers of US-treated rats the AD-hydroxylase activity did not differ from the control, thus suggesting that CYP2A1, CYP2B1, CYP2C11, CYP3A1 were not induced. The rate of ER-deethylation increased from 100 in control up to 300 pmol/min/mg in US-treated rats. Western blot analysis revealed also the CYP1A1 induction in US-treated rats which was absent in untreated animals. The mRNA level for CYP1A1 in the livers of US-treated rats increased from 0.5 up to 6.0 fmol mRNA/total RNA but did not change for CYP1A2. The results obtained provide evidence for the nonchemical induction of CYP4501A1 which is known to be induced by polycyclic aromatic compounds as well as by some other compounds.

[The characteristics of the effect of centimeter-range microwaves on drug pharmacokinetics in the body of experimental animals]. / Osobennosti vliianiia mikrovoln santimetrovogo diapazona na farmakokinetiku medikamentov v organizme éksperimental'nykh zhivotnykh.

The experiments on 130 rat males have shown that the exposure of the animals' liver to centimeter microwaves enhances catalytic activity of P-450p cytochrome, an enzyme of drug microsomal metabolism. However, changes in pharmacokinetic parameters of elimination from the blood of the drugs based on microsomal substrates of hepatic enzymatic system are more dependent on the microwaves' impact on physiological factors modifying drug pharmacokinetics. This implies the necessity of pharmacokinetic investigations in each individual case of combining drugs with microwaves.

[Induction of cytochromes P-4501A and 2B in various rat organs, subjected to hexachlorobenzene and aroclor 1254]. / Induktsiia tsitokhormov P-4501A i 2B v raznykh organakh krys, poluchavshikh geksakhlorbenzol i arokhlor 1254.

The activity and content of CYP1A1, CYP1A2, CYP2B1 and CYP2B in the liver, lung and kidney of Wistar rats treated with hexachlorobenzene (HCB), Aroclor 1254 (AR), methylcholanthrene (MC) and phenobarbital (PB) were studied. Administration of MC and AR caused an increase in the ethoxyresorufin (ER) and methoxyresorufin (MR)-O-dealkylase activities in all organs. The effect of HCB on lung and kidney monooxygenases was considerably lower. The penthoxyresorufin (PR)-O-dealkylase activity in extrahepatic organs was at the same level for all treatments used in this study. Western blot analysis using monoclonal antibodies against CYP1A and CYP2B also revealed a tissue-specific expression of these proteins during different inductions. Whereas in the liver during MC, AR and HCB inductions one revealed immunologically identical CYP1A1 and CYP1A2, in MC lung only CYP1A1 was observed. In the lung of AR and HCB microsomes both CYP1A1 and CYP1A2 were found. In the kidney after treatment with AR or HCB only CYP1A1 was induced. These findings suggest that inducers of mixed type cause coordinated synthesis of CYP1A1 and CYP1A2 in the lung unobserved during MC induction. After treatment of rats with PB both CYP2B1 and CYP2B2 were observed in the liver, while only the former was found in the lung and kidney. HCB treatment did not significantly affect the induction picture. In the liver and lung of AR-treated rats, besides CYP2B1 and CYP2B2, one more P-450 was revealed whose nature is under discussion now. The data obtained thus suggest that induction of different P-450s is not only tissue-specific but also depends on the inducer type.

[Interaction of perfluoroctylbromide with liver microsomal monooxygenase]. / Vzaimodeistvie perftorktilbromida s mikrosamal'noi monoksigenazoi pecheni.

Perfluorooctylbromide (PFOB), a constituent component of gas-transporting fluorocarbon emulsions, liberates bromide ions when PFOB undergoes NADPH-dependent metabolism by liver microsomal monooxygenase. The PFOB emulsion injected to rats decreases the liver microsomal cytochrome P-450 level down to 80% of control. Induction of the "phenobarbital" isoforms of cytochrome P-450 (cytochrome P-450 II B1/B2) after administration of PFOB is much weaker than that after administration of the perfluorodecalin emulsion. It is suggested that the anomalous cytochrome P-450-inductive properties of PFOB may be associated with its ability to be metabolized by liver microsomal monooxygenase. In these terms, the generally accepted viewpoint about the biological inertness and unchangeability within the organism of perfluorochemicals containing heteroatoms (N, O, H and others) and double bonds, needs further verification and experiment.

[The effect of tetrahydrofuran on the microsomal monooxygenase system in vitro and in vivo]. / Vliianie tetragidrofurana na mikrosomnuiu mooksigenaznuiu sistemu in vitro i in vivo.

The effects of tetrahydrofuran (THF) on rat liver microsomes in vitro and in vivo were opposite. In vitro THF inhibited the p-nitrophenol (PNP) hydroxylase activity of microsomes from control rats and from rats treated with PB, acetone, and isoniazide--by 50, 20, 60, and 80%, respectively. THF inhibited dimethylnitrosamine (NDMA) demethylation in control and induced microsomes in a lesser degree. THF increased the total cytochrome P-450 content as well as the contents of cytochromes P-450IIE1 and P-450IIB1/B2. The activities of PNP-hydroxylation and NDMA-demethylation increased also, whereas the PR-dealkylation activity was unchanged. An increase in the THF dose caused inhibition of the rat liver microsomal monooxygenase system.

[The effect of pyridine and pyridine-N-oxide on the monooxygenase system of rat liver microsomes]. / Vliianie piridina i piridin-N-oksida monoksigenaznuiu sistemu mikrosom pecheni krys.

Effects of pyridine and pyridine-N-oxide on the monooxygenase system of rat liver microsomes have been studied. Pyridine (200 mg/kg) increased total cytochrome P-450 content and activated metabolism of some specific substrates 24 hours after injection. There was an increase in the degree of p-nitrophenol and chlorzoxazone hydroxylation due to increasing ethanol-induced cytochrome P-450IIE1 content. Pyridine was also able to induce cytochrome P-450IIB1 in rat microsomes; this reaction was accompanied by acceleration of 7-pentoxyresorufin 0-dealkylation. Cytochrome P-450IA1 appearance in liver microsomes was associated with increasing content of cytochrome P-450IA2. Dealkylation rates for specific substrates (7-ethoxyresorufin and 7-methoxyresorufin) were also increased. Similar to pyridine, pyridine-7-oxide induced cytochromes P-450IIE1, P-450IIB1/B2, and P-450IA1/A2, resulting in activation of specific substrate metabolism. Hence, pyridine and its derivative pyridine-N-oxide can be regarded as effective inducers of cytochrome P-450.

[Mechanism of inhibiting the cytochrome P-450-dependent monooxygenase system in liver with fluorocarbons]. / Mekhanizm ingibirovaniia tsitokhrom P-450-zavisimoi monooksigenaznoi sistemy pecheni ftoruglerodami.

The inducer of the liver monooxygenase system perfluorodecalin added to microsomes as a submicron emulsion forms an enzyme-substrate complex with cytochrome P-450. The K(app) values for the perfluorodecalin binding to cytochrome P-450 in microsomes isolated from the livers of control and phenobarbital-treated rats are 5 x 10(-5) M and 2.3 x 10(-6) M, respectively. Perfluorodecalin competitively inhibits the binding of substrates to cytochrome P-450 and decreases the rates of monooxygenase reactions. Perfluorodecalin extrusion from the active center of cytochrome P-450 occurs when an excess of perfluorocarbons non-interacting with cytochrome P-450 is added to microsomes. There is a significant vagueness in the rates of various monooxygenase reactions because of simultaneous induction and inhibition of monooxygenase enzymes after perfluorodecalin administration to rats. The data obtained are consistent with the hypothesis that constitutive forms of cytochrome P-450 are primary receptors for xenobiotic-inducers of phenobarbital-type cytochrome P-450 isoforms.

[Activity of cytochromes P-450p and P-450h in liver microsomes and blood corticosteroid levels in experimental animals under the action of physical factors]. / Aktivnost' tsitokhromov P-450p i P-450h mikrosom pecheni i uroven' kortikosteroidov v krovi éksperimental'nykh zhivotnykh v usloviiakh vozdeistviia fizicheskimi faktorami.

In experiments on male Wistar rats it has been found that physical factors applied in medicine (laser radiation of low intensity with wave length 0.89 microns, microwaves of centimeter range of 2450 MHz, and ultrasound of low intensity 880 KHz) changed catalytic activity of liver microsomal and rostenedione 16 alpha- and 6 beta-hydroxylating cytochromes P-450h and P-450p and blood corticosteroids level. Activities of these two steroid-metabolizing cytochromes decreased under ultrasonic skin application on liver region and increased under microwave and laser action. Contents of physiologically inactive form of corticosterone were not changed by the physical factors action while level of active hormone was increased under ultrasonic and microwave action. These findings suggest association of the activity of liver steroid-metabolizing cytochromes P-450 and level of physiologically active form of corticosterone in blood under physical factors skin application on liver region.

[Benzonal--a phenobarbital-type of inducer of the mono-oxygenase system]. / Benzonal--induktor monooksigenaznoi sistemy fenobarbitalovogo tipa.

It has been found that the Soviet anticonvulsant drug Benzonal is an inducer of the liver cytochrome P-450 of the phenobarbital type. The drug causes formation of the cytochrome P-450 form which is immunologically identical to the phenobarbital inducible form of the hemoprotein with identical molecular mass determined with the SDS-gel electrophoresis method in PAAG. The microsomes, obtained from the rats treated with Benzonal display increased rates of metabolism of 7-pentoxiresorufin and 16 beta-hydroxylation of androstenedione which are specific substrates for the cytochrome P-450b.

[Theophylline metabolism by rat liver microsomal monooxygenases]. / Metabolizm teofillina mikrosomnymi monooksigenazami pecheni krys.

Theophylline metabolism has been studied in a reconstituted monooxygenase system with purified forms of cytochrome P-450: P-450a, P-450b, P-450d and P-450k as well as in liver microsomes of control and 3-methylcholanthrene-induced rats. Cytochrome P-450 isoforms, P-450a and P-450b, had no effect on theophylline metabolism, whereas forms P-450d and P-450k induced the synthesis of 1.3-dimethyluric acid (1.3-DMA) at the rates of 900 and 330 pmol/min/nmol of protein, respectively. The catalytic activity of these isoforms was fully inhibited by homologous monospecific antibodies. P-450c catalyzed the formation of a nonidentified metabolite. In microsomes of control animals antibodies specifically directed to cytochrome P-450k suppressed the rate of 1.3-DMA synthesis by 73%, whereas antibodies specifically raised against P-450c+d--by 11%. In microsomes of methylcholanthrene-induced animals the rate of 1.3-DMA synthesis was increased two-fold. This activity was inhibited by 61% by antibodies to cytochrome P-450k and by 18% by anti-P-450c+d antibodies.

[Diazepam metabolism by multiple forms of cytochrome P-450 in rat liver microsomes]. / Metabolizm diazepama mnozhestvennymi formami tsitokhroma P-450 mikrosom pecheni krys.

The synthesis of pharmacologically active diazepam metabolites (oxazepam, 4-hydroxydiazepam, N-demethyldiazepam) in liver microsomes of intact and phenobarbital-, 3-methylcholanthrene- and dexamethasone-induced male and female Wistar rats as well as in a reconstituted system with isolated forms of cytochrome P-450 (P-450a, P-450b, P-450c, P-450d and P-450k according to the Ryan nomenclature) was studied. Marked sex-dependent differences in the rates of diazepam metabolism in liver microsomes of intact and induced animals were revealed. The changes in the spectrum of diazepam metabolites in liver microsomes of induced rats (as compared to control animals) were revealed. In a reconstituted system only phenobarbital-induced cytochromes P-450b and P-450k were found to be active participants of diazepam N-demethylation; none of the isoenzymes tested were shown to be involved in diazepam hydroxylation.

[Induction of cytochrome P-450 forms by prolonged administration of nifedipine]. / Induktsiia form tsitokhroma P-450 pri dlitel'nom vvedenii nifedipina.

In experiments on male Wistar rats it has been found that nifedipine applied in a dose of 10 mg/kg body weight i.p. daily for 20 days did not significantly increase the total amount of cytochrome P-450 but markedly increased the 7 alpha-, 16 beta- and 6 beta-hydroxylation of androstenedione in liver microsomes, suggesting the induction of cytochromes P-450a, P-450b and P-450p respectively. The induction of cytochrome P-450b was also confirmed immunochemically with polyclonal antibodies against cytochrome P-450b/e.