Microwave frequency comb Doppler reflectometer applying fast digital data acquisition system in LHD

We succeeded in increasing the radial observation points of the microwave frequency comb Doppler reflectometer system from 8 to 20 (or especially up to 45) using the high sampling rate of 40 GS/s digital signal processing. For a new acquisition system, the estimation scheme of the Doppler shifted frequency is constructed and compared with the conventional technique. Also, the fine radial profile of perpendicular velocity is obtained, and it is found that the perpendicular velocity profile is consistent with the E × B drift velocity one.

Association of habitual long-distance running with the thickness of skeletal muscles and subcutaneous fat in the body extremities and trunk in middle-aged men

AIM

We investigated the association of habitual long-distance running with the thickness of skeletal muscles and subcutaneous fat in the body extremities and trunk in middle-aged men using ultrasonography.

METHODS

Three groups of healthy middle-aged men [mean (SD), 62.1 (2.8) years] took part in this investigation: a high-level group of 11 master runners who had competed in a 42.195 km race and run 51.6 (21.7) km every week, an intermediary-level group of 10 master runners who had competed in a 5-20 km race and run 9.3 (4.9) km every week, and a low-level group of 7 untrained men who continued to do no systematic training. The muscle thickness at 8 sites and the subcutaneous fat thickness at 10 sites were measured by B-mode ultrasonography, and were compared among the 3 groups.

RESULTS

The high-level group had 10.0(-1)5.2% higher values for muscle thickness at the erector spinae, hamstrings, tibialis anterior, and triceps surae, compared with the intermediary-level and the low-level groups (p<0.05-0.001). The thickness of the subcutaneous fat about the rectus abdominis and external oblique was lower in the high-level group than in the intermediary-level and the low-level groups (p<0.05).

CONCLUSIONS

Middle-aged male master athletes who habitually run at a high level have more muscle thickness in the lower extremities and trunk, and less subcutaneous fat thickness in the central regions of the body than do middle-aged men who habitually run at an intermediary level or do not run at all.

Simultaneous expression of guinea pig UDP-glucuronosyltransferase 2B21 and 2B22 in COS-7 cells enhances UDP-glucuronosyltransferase 2B21-catalyzed morphine-6-glucuronide formation

Although UDP-glucuronosyltransferases (UGTs) act as an important detoxification system for many endogenous and exogenous compounds, they are also involved in the metabolic activation of morphine to form morphine-6-glucuronide (M-6-G). The cDNAs encoding guinea pig liver UGT2B21 and UGT2B22, which are intimately involved in M-6-G formation, have been cloned and characterized. Although some evidence suggests that UGTs may function as oligomers, it is not known whether hetero-oligomer formation leads to differences in substrate specificity. In this work, evidence for a functional hetero-oligomer between UGT2B21 and UGT2B22 is provided by studies on the glucuronidation of morphine in transfected COS-7 cells. Cells transfected with UGT2B21 cDNA catalyzed mainly morphine-3-glucuronide formation although M-6-G was also formed to some extent. In contrast, cells transfected with UGT2B22 cDNA did not show any significant activity toward morphine. When UGT2B21 and UGT2B22 were expressed simultaneously in different ratios in COS-7 cells, extensive M-6-G formation was observed. This stimulation of M-6-G formation was not observed, however, when microsomes containing UGT2B21were mixed with those containing UGT2B22 in the presence of detergent. Furthermore, this effect was not very marked when human UGT1A1 and UGT2B21 were coexpressed in COS-7 cells. This is the first report suggesting that UGT hetero-oligomer formation leads to altered substrate specificity.

Identification of the core protein carrying the Tn antigen in mouse brain: specific expression on syndecan-3

We isolated glycoproteins carrying the Tn antigen, which was expressed spatiotemporally in the developing mouse brain. The Tn antigen was expressed on two molecular species with a molecular weight from 200 to 350 kDa and 110 to 160 kDa, as judged on SDS-PAGE. Although the two glycoproteins showed different susceptibilities to heparitinase I and solubilities in a salt solution, after treatment with V8 protease they showed the same mobility corresponding to a molecular weight of 90 kDa on SDS-PAGE, suggesting that these two molecules shared a common core protein. Partial N-terminal sequences of the glycoproteins were determined, i.e. AQRXRNENFERPV and ALAAPXAPAMLP, which were identified as the sequences of the N-terminal and central portions of syndecan-3, respectively. Both glycoproteins were reactive to anti-mouse syndecan-3 antibody. These results suggest that one is a soluble syndecan-3 cleaved between mucin-like domain and transmembrane domain, and the other is a membrane-bound syndecan-3 lacking N-terminal glycosaminoglycan attachment sites, and that both glycoproteins have a mucin-like domain characteristic of syndecan-3, in which the Tn antigen may be expressed.

Developmental expression of a unique carbohydrate antigen, Tn antigen, in mouse central nervous tissues

Using an anti-Tn monoclonal antibody, the Tn antigen was detected immunohistochemically in prenatal and early postnatal central nervous tissues. On embryonic day 9 (E9), the antigen was distributed throughout the single neuroepithelial layer in the neocortex and then became more prominent in the preplate than in the ventricular zone along with formation of the preplate. Following division of the preplate and concomitant formation of the cortical plate, distinct labeling of the neocortex occurred in the marginal, subplate and intermediate zones, whereas in the cortical plate and ventricular zone were virtually not immunostained. It is notable that thalamocortical afferent fibers were also immunostained specifically on E14. After birth, the localization of the antigen became less noticeable and by 3 weeks after birth, the antigen had substantially disappeared. In the developing cerebellum, prominent labeling was also observed in the molecular layer and outskirts of the cerebellar nuclei on early postnatal days. To characterize the glycoprotein bearing the Tn antigen biochemically, immunoblot analysis was performed. The glycoprotein, most of which was extracted with a salt solution, migrated as a broad smeared band corresponding to a molecular weight of about 250 kDa on SDS-PAGE. Among the various tissues examined, this glycoprotein was only detected in the brain and its amount increased until an early postnatal stage with a peak on postnatal day 3 (P3), and then decreased gradually with age. This spatially and developmentally regulated expression of the Tn antigen suggests that this antigen plays a significant role in brain development.

[Suppression of stress proteins, GRP78, GRP94, calreticulin and calnexin in liver endoplasmic reticulum of rat treated with a highly toxic coplanar PCB]

The present study was addressed on the effect of 3,3',4,4',5-pentachlorobiphenyl (PenCB) to the expression of molecular chaperon proteins, glucose regulated protein (GRP) 78, GRP94, calreticulin and calnexin in liver endoplasmic reticulum of rat by treatment with acute exposure. Male Wistar rats received PenCB in corn oil at once a dose of 10 mg/kg i.p., then at 5 days after treatment the microsomes were prepared. Free-fed and pair-fed control groups were given the vehicle. The microsomal proteins were separated on SDS-PAGE, transferred to membrane and blotted using antibody towards respective chaperone proteins. The protein levels of GRP78, GRP94, calreticulin and calnexin were significantly decreased with the acute exposure. In addition, albumin level in the microsomes was also significantly reduced by the PenCB treatment. The transferrin level was significantly higher than pair-fed but not from free-fed group. These chaperone proteins have important physiological functions against synthesized and/or denatured proteins, which include assembling, folding of proteins. PenCB-treatment may alter the extent of biosynthesis of secretory protein such as albumin through the decreasing levels of chaperone proteins in endoplasmic reticulum. Interestingly, reduced GRP78 protein level by PenCB was not due to decreased mRNA level. Our results suggested that a part of the toxicity of PenCB is associated to significant decrease of the chaperone proteins in the endoplasmic reticulum.

Effects of a highly toxic coplanar polychlorinated biphenyl, 3,3',4,4',5-pentachlorobiphenyl on intermediary metabolism: reduced triose phosphate content in rat liver cytosol

The effects of a highly toxic coplanar polychlorinated biphenyl, 3,3',4,4',5-pentachlorobiphenyl (PenCB), on triose phosphate metabolizing enzymes were studied. Male Wistar rats received 25 mg/kg PenCB, i.p. At this dose the compound provokes a wasting syndrome. The activity of triose phosphate metabolizing enzymes, glyceraldehyde-3-phosphate dehydrogenase, triose phosphate isomerase, glycerokinase, transaldolase and transketolase were significantly reduced by PenCB treatment to 50%, 60%, 50%, 70% and 40% of free-fed controls, respectively. An inhibition study with pyrazol, a specific inhibitor of alcohol dehydrogenase (ADH), showed that ADH makes about a 30% contribution to the formation of glycerol-3-phosphate from glyceraldehyde-3-phosphate. Our current study revealed that PenCB suppresses ADH at the protein expression level. The reduced formation of glycerol-3-phosphate from glyceraldehyde dehydrogenase by PenCB could be due to the suppression of ADH. The triose phosphate content in the liver cytosol of PenCB-treated rats was significantly lower than in free-fed controls. The suppression of triose phosphate metabolism could be a cause of the wasting syndrome provoked by highly toxic coplanar PCB.

Sequence analyses of CYP2B genes and catalytic profiles for P450s in Qdj:Sprague-dawley rats that lack response to the phenobarbital-mediated induction of CYP2B2

The Qdj:Sprague-Dawley (SD) rat is a mutant strain lacking in phenobarbital (PB)-mediated induction of CYP2B2. The presence of interindividual differences in the hepatic content of CYP2B proteins and testosterone 16beta-hydroxylase activity demonstrated that the breeding colony of Qdj:SD rats involves normal (+/+) and intermediate (+/-) phenotypes as well as mutant (-/-)-type rats. Although PB-treated Qdj:SD (-/-) rats expressed CYP2B1 normally, testosterone 16beta-hydroxylase activity in these rats was quite low. Analysis of regioselective metabolism of testosterone and 4-hydroxybiphenyl glucuronidation demonstrated normal catalytic activities associated with other forms of cytochrome P450s, including CYP2A, -2C, and -3A, as well as PB-inducible UDP-glucuronosyltransferase in Qdj:SD (-/-) rats. There were no serious mutations in the exons of the CYP2B1 gene in Qdj:SD (-/-) rats, demonstrating that this gene codes a functional CYP2B1. These observations suggest that CYP2B1 needs the interaction with CYP2B2 to exert the full function. The CYP2B2 gene in Qdj:SD (-/-) rats was the same as that in wild-type (+/+) rats in its length of the region containing all exon/introns and 5'-upstream up to -2.3 kilobase pairs. Malignant mutation such as stop codon formation was not observed in the exons, and no mutation was detected in the region containing the PB-responsive unit. These results strongly suggest that impaired induction of CYP2B2 in Qdj:SD (-/-) rats is attributable either to mutation at the region different from PB-responsive unit and exons or to absence or lowered expression of trans-acting factor(s) necessary for gene regulation.

Suppression of the expression of the CYP2B1/2 gene by retinoic acids

The effects of 5alpha-androsten-3alpha-ol (ASE), and retinoic acids (RAs) and their precursors on the phenobarbital (PB)-mediated induction of CYP2B1 and 2B2 were examined in cultured rat hepatocytes. Two isomers of RA, 9-cis- and all-trans-RA, suppressed markedly the effect of PB on CYP2B1/2 expression, while ASE had no suppressive effect. The effect of 9-cis-RA appeared at a lower concentration than the all-trans-isomer, indicating the dominant action of the former isomer. Suppression with 9-cis-retinal was also observed, but all-trans-retinol and -retinal were without effect. These results suggest that: (1) ASE, an inverse agonist for the constitutive androstane receptor (CAR), does not play a major role in the suppression of the CYP2B; (2) 9-cis-RA suppresses CYP2B induction by reducing ligand-free retinoid X-receptors (RXR) available for dimerization with the CAR; and (3) enzymes responsible for RA formation play an important role in the mechanism governing CYP2B regulation.

Characteristic glucuronidation pattern of physiologic concentration of morphine in rat brain

Formation of conjugated metabolites from morphine at a very low level in brain was studied in vitro in rats. Incubation of a low concentration of 3H-morphine with brain homogenate followed by two successive high-performance liquid chromatographic analyses showed that endogenous morphine is converted by brain enzymes to its 3- and 6-glucuronides (M-3-G and M-6-G), and codeine glucuronide (Cod-G). However, the formation of morphine-6-sulfate was likely to be low if it was produced at all. All of the cerebral hemisphere, brain stem and cerebellum were capable of producing M-3-G, M-6-G and Cod-G, although there were differences in selectivity. The capacity of the brain for glucuronide formation was far less than that of the liver, but UDP-glucuronosyltransferase in brain was much more selective in forming M-6-G and Cod-G than liver enzymes.

Suppression of carbonic anhydrase III in rat liver by a dioxin-related toxic compound, coplanar polychlorinated biphenyl, 3, 3',4,4',5-pentachlorobiphenyl

A coplanar polychlorinated biphenyl, 3,3',4,4',5-pentachlorobiphenyl (PenCB), significantly suppresses the expression of rat liver carbonic anhydrase III (CAIII), an enzyme which has recently been suggested to prevent from H(2)O(2)-inducible apoptosis. Marked changes in the CAIII levels of liver cytosol were observed in rats following doses of PenCB ranging from 0.5 to 25 mg/kg body weight and maximum suppression was observed at a dose of 10 mg/kg. Northern analysis revealed that the level of CAIII mRNA in rat liver was dramatically reduced by PenCB treatment while only weak suppression was observed in pair-fed controls. Two AU-rich elements, considered as a destabilizing signal of mRNA, were found in the 3'-untranslated region of CAIII sequenced after reverse transcription-PCR and 3'-rapid amplification of the cDNA end. Dramatic decrease of CAIII in rat liver by PenCB could account for the suppression of the defense system for oxidative stress.

Interaction between cytochrome P450 and other drug-metabolizing enzymes: evidence for an association of CYP1A1 with microsomal epoxide hydrolase and UDP-glucuronosyltransferase

Protein-protein interactions between cytochrome P450 (P450) and other drug-metabolizing enzymes were studied by affinity chromatography using CYP1A1-, glycine-, and bovine serum albumin (BSA)-conjugated Sepharose 4B columns. Sodium cholate-solubilized microsomes from phenobarbital-treated rat liver were applied to the columns and the material eluted with buffer containing NaCl was analyzed by immunoblotting. Microsomal epoxide hydrolase (mEH) and UDP-glucuronosyltransferases (UGTs), as well as NADPH-P450 reductase, were efficiently trapped by the CYP1A1 column. Glycine and BSA columns exhibited no ability to retain these proteins. Protein disulfide isomerase and calnexin, non-drug-metabolizing enzymes expressed in the endoplasmic reticulum, were unable to associate with the CYP1A1 column. These results suggest that CYP1A1 interacts with mEH and UGT to facilitate a series of multistep drug metabolic conversions.

Simple and practical sandwich-type enzyme immunoassay for human oxidatively modified low density lipoprotein using antioxidized phosphatidylcholine monoclonal antibody and antihuman apolipoprotein-B antibody

OBJECTIVES

To develop a simple and practical enzyme immunoassay (EIA) for oxidatively modified low density lipoprotein (Ox-LDL) in human blood, a biological marker of atherogenesis.

DESIGN AND METHODS

A sandwich EIA suitable for the measurement of human Ox-LDL was developed using the mouse monoclonal antibody FOH1a/DLH3. This antibody, specific for oxidized phosphatidylcholine, was used as the capture antibody, and a horseradish peroxidase (HRP)-labeled goat anti-human apolipoprotein-B (Apo-B) IgG was used for detection. Copper-oxidized human LDL, prepared under controlled conditions, was used as a standard and the results of the EIA were expressed in arbitrary units (U/mL).

RESULTS

This EIA meets all the requirements for use in routine clinical assays in terms of sensitivity (detection limit: 1 U/mL), reproducibility (total CV: 2.3-7.7%), accuracy (recovery: 90.6-103.8%), simplicity and rapidity (<4 h). Clinical performance of the assay was assessed by measurement of the Ox-LDL in the plasma of normal subjects (10.8 +/- 2.8 U/mL, mean +/- SD) and patients with coronary heart disease (CHD) (19.7 +/- 10.2). The present EIA had a sensitivity of 79% and a specificity of 75% for CHD.

CONCLUSIONS

We have developed a new assay, suitable for the measurement of Ox-LDL in human blood, which meets the requirements for routine clinical assay.

Participation of syndecan 2 in the induction of stress fiber formation in cooperation with integrin alpha5beta1: structural characteristics of heparan sulfate chains with avidity to COOH-terminal heparin-binding domain of fibronectin

The present study provides direct evidence that syndecan 2 participates selectively in the induction of stress fiber formation in cooperation with integrin alpha5beta1 through specific binding of its heparan sulfate side chains to the fibronectin substrate. Our previous study with Lewis lung carcinoma-derived P29 cells demonstrated that the cell surface heparan sulfate proteoglycan, which binds to fibronectin, is syndecan 2 (N. Itano et al., 1996, Biochem. J. 315, 925-930). We here report that in vitro treatment of the cells by antisense oligonucleotide for syndecan 2 resulted in a failure to form stress fibers on fibronectin substrate in association with specific suppression of its cell surface expression. Instead, localization of actin filaments in the cytoplasmic cortex occurred. A similar response of the cells was observed when the cells were treated to eliminate functions of cell surface heparan sulfates, including exogenous addition of heparin and pretreatment with anti-heparan sulfate antibody, F58-10E4, and with proteinase-free heparitinase I. Size- and structure-defined oligosaccharides prepared from heparin and chemically modified heparins were utilized as competitive inhibitors to examine the structural characteristics of the cell surface heparan sulfates involved in organization of the actin cytoskeleton. Their affinity chromatography on a column linked with a recombinant H-271 peptide containing a C-terminal heparin-binding domain of fibronectin demonstrated that 2-O-sulfated iduronates were essential for the binding. Inhibition studies revealed that a heparin-derived dodecasaccharide sample enriched with an IdoA(2OS)-GlcNS(6OS) disaccharide completely blocked binding of the syndecan 2 ectodomain to immobilized H-271 peptide. Finally, the dodecasaccharide sample was shown to inhibit stress fiber formation, triggered by adhesion of P29 cells to a CH-271 polypeptide consisting of both the RGD cell-binding and the C-terminal heparin-binding domains of fibronectin in a fused form. All these results consistently suggest that syndecan 2 proteoglycan interacts with the C-terminal heparin-binding domain of fibronectin at the highly sulfated cluster(s), such as [IdoA(2OS)-GlcNS(6OS)](6) present in its heparan sulfate chains, to result in the induction of stress fiber formation in cooperation with integrin alpha5beta1.

A highly toxic coplanar polychlorinated biphenyl compound suppresses Delta5 and Delta6 desaturase activities which play key roles in arachidonic acid synthesis in rat liver

The effect of 3,3',4,4',5-pentachlorobiphenyl (PenCB) on the synthesis of unsaturated fatty acids was studied in male Wistar rats. The arachidonic acid (20:4) content in the total lipids of liver homogenates was significantly reduced on day 5 of PenCB administration, while those of linoleic acid (18:2) and bishomo-gamma-linolenic acid (20:3) were increased. These changes in the total lipids of liver homogenates were observed following doses of PenCB ranging from 0.5 to 25 mg/kg of body weight. The same changes in these fatty acids were seen with four subtypes of microsomal glycerophospholipids in the liver. The marked reduction in the molar ratio of 20:4 to 18:2 in the lipids suggests alteration of the activity of the enzymes responsible for the synthesis of unsaturated fatty acids. The activity of Delta5 and Delta6 desaturases (arachidonic acid synthetase) in the liver microsomes was 17 and 13% of that of pair-fed control animals, whereas the activity of 1-acylglycerophosphorylcholine or 1-acylglycerophosphate acyltransferase, which transfers 20:4 or 18:2 to phospholipids, was not affected by the treatment. Thus, the reduction in the level of 20:4 that was observed can be explained by a reduction in desaturase activity. These results are evidence that the coplanar PenCB has a significant effect on the reduced synthesis of physiologically essential long-chain unsaturated fatty acids.

Effect of a ligand selective for peripheral benzodiazepine receptors on the expression of rat hepatic P-450 cytochromes: assessment of the effect in vivo and in a hepatocyte culture system

The peripheral benzodiazepine receptor plays a role in the translocation of cholesterol into mitochondria where steroidogenesis occurs. Sterols have been suggested to be involved in the regulation of the cytochrome P-450 (CYP)2B subfamily as the endogenous suppressor of this CYP. To investigate the role of cholesterol metabolites on the expression of CYPs, the effect of PK11195, a specific ligand of the peripheral benzodiazepine receptor and a stimulator of cholesterol transportation, on CYP expression was examined in rats in vivo and in cultured hepatocytes. As judged by the change in testosterone metabolic activity catalyzed by liver microsomes, i.p. injection of PK11195 into rats increased the CYP2B subfamily significantly. A trend in the induction of the CYP2A1, 2C11, and 3A isozymes was also observed. When PK11195 was given to rats together with phenobarbital, an additive effect of these compounds on testosterone metabolic activity was observed. In cultured hepatocytes, PK11195 exhibited the same effect on CYP expression as seen in vivo, but the magnitude of the effect was much greater than that observed in vivo. The inductive effect of PK11195 toward the CYP2B and 3A subfamilies was 2.3- and 6.5-fold greater, respectively, than that with phenobarbital. The inductive effect of PK11195 was confirmed by immunoblotting with antibodies against CYP2A, 2B, 2C, and 3A proteins. These results indicate that PK11195 has an inductive effect on several subfamilies of CYPs by directly acting on liver cells and has no ability to suppress the expression of these CYPs. This observation suggests that, if certain sterols play a role in the suppressive control of the CYP2B subfamily, they are produced in organelles other than the mitochondria.

[Suppression of stress proteins in endoplasmic reticulum in liver cytosol of rats treated with a highly toxic coplanar PCB]

The present study was addressed on the effect of 3,3',4,4',5-pentachlorobiphenyl (PenCB) to the expression of glucose regulated protein (GRP) 78 and GRP94 in liver endoplasmic reticulum of rat by treatment with the schedule after acute or subacute exposure. In the acute exposure, male Wistar rats received PenCB in corn oil at once a dose of 25 mg/kg i.p., then at 5 days after treatment the microsomes were prepared. Free- and pair-fed control groups were given the vehicle. The microsomal proteins were separated on SDS-PAGE, transferred to membrane and blotted using anti-sera to the GRPs. The reduction of GRP78 and GRP94 was associated significantly with the acute exposure. In subacute exposure, the rats received PenCB in corn oil at once a dose of 0.1 or 1.0 mg/kg i.p. At 4 weeks after treatment, liver microsomes were obtained. The expression level of GRP78 and GRP94 are also decreased at 1.0 mg PenCB/kg treatment as similar as the acute exposure. But the reduction was not notable at 0.1 mg PenCB/kg treatment. GRP78 and GRP94 are a member of GRPs and the expression is regulated by glucose in cells as stress proteins. GRP78 and GRP94 have also the function for chaperone protein. Chaperone proteins have important physiological functions against synthesized and/or denatured proteins, which include assembling, folding of proteins. Our results suggested that a part of the toxicity of PenCB is associated to significant decrease of the chaperone proteins in the endoplasmic reticulum.

[Induction of molecular chaperones HSP70 and HSP90 in rat liver cytosol by a highly toxic coplanar PCB]

We report here that a highly toxic coplanar polychlorinated biphenyl (PCB), 3,3',4,4',5-pentachlorobiphenyl (PenCB) induces molecular chaperones, HSP70 and HSP90 in liver cytosol of rats. Male Wistar rats received PenCB in corn oil once at a dose of 25 mg/kg i.p. Pair-fed control groups were treated with the vehicle and given the amount of chow matched with that taken by the PenCB-treated animals, and free-fed controls were given the vehicle. The liver cytosolic HSP70 level in rats treated with PenCB was 5-fold higher than those in free-fed controls, though that for pair-fed controls was approximately 2-fold higher than that in free-fed controls. The liver cytosolic HSP90 alpha and HSP90 beta levels were also higher in PenCB-treated rats than in both control groups, but the induction extent was lesser than that for HSP70. Inductive effect on the chaperones was examined with a single different dose of PenCB 0, 0.5, 1.0, 5.0, 10 and 25 mg/kg. Marked induction of the HSP70 level was observed with a minimum dose of PenCB 0.5 mg/kg. The HSP90 alpha level was induced with PenCB-dose dependent manner although the HSP90 beta induction was greatest with a dose of PenCB 5.0 mg/kg. HSP70 and HSP90 are essential for cells under normal conditions and act as molecular chaperones. HSP90 is well known to modulate the function of sex steroid hormone or aromatic hydrocarbon receptors while HSP70 is required for receptor-HSP90 heterocomplex assembly. The role of molecular chaperones may be involved in the endocrine disrupting properties of coplanar PCB and dioxins.

Induction of a cytosolic 54 kDa protein in rat liver that is highly homologous to selenium-binding protein

We have previously shown that a 54 kDa protein in rat liver is highly homologous to selenium-binding protein (SeBP) or acetaminophen-binding protein (APBP) in mice and is highly inducible by treatment with 3,3',4,4',5-pentachlorobiphenyl or 3-methylcholanthrene. In this study, we examine the effect of six typical inducers, 3-methylcholanthrene (MC), isosafrole (ISO), phenobarbital (PB), dexamethasone (DEX), clofibrate (CLO), pyrazole (PYR) and butylated hydroxytoluene (BHT), on the expression level of this 54 kDa protein. Male Wistar rats were given each inducer following a predetermined schedule. Among these inducers, the 54 kDa protein was inducible by MC and BHT. The response to MC and BHT was compared with that of NAD(P)H: quinone oxidoreductase and ethoxyresorufin O-deethylase activities. The induction mechanisms and physiological role of the 54 kDa protein are discussed in the light of our results.

Induction of rat hepatic cytochromes P450 by toxic ingredients in plants: lack of correlation between toxicity and inductive activity

"Animal-Plant Warfare" is one of the hypotheses for the evolution of drug-metabolizing P450s. To address the validity of this hypothesis, we examined the induction of xenobiotic-metabolizing P450s by 12 plant toxins in rats, using hepatic activity for testosterone metabolism as the index. The compounds tested were aconitine, morphine, tubocurarine, physostigmine, pilocarpine, muscarine, cocaine, atropine, amygdalin, digitonin, nicotine and solanine. Drinking water containing a test compound was given to rats for 4 days, and the hepatic activity of testosterone metabolism was determined together with monitoring body weight gain and liver weight as the indices of toxicity. The results showed that while cocaine and nicotine have a minor ability to increase testosterone 16 beta-hydroxylase activity, a marker activity for the CYP2B1 and 2, all other compounds did not have any such effect. No correlation was observed between a change in 16 beta-hydroxylase and toxicity caused by toxins. Therefore, these results did not support the idea that the inducibility of the CYP2B subfamily in animals is acquired through "Animal-Plant Warfare". Several compounds examined here increased or decreased hepatic activities of testosterone 2 alpha-, 6 beta-, 7 alpha- and 16 alpha-hydroxylation and 17-oxidation, indicating a possible effect on the CYP2A, 2C and 3A subfamily. Of these effects, a moderate correlation (r < 0.49) was observed in the changes in the activities of 2 alpha-/16 alpha-hydroxylation and 17-oxidation vs. that in toxicity. It is therefore suggested that inhibition or suppression of the expression of CYP2C11 is one of the mechanisms in the toxicity of plant toxins for rats, although it comes from an examination using limited numbers of compounds.

Phenobarbital-mediated induction of the CYP2B subfamily is not antagonized by picrotoxin, a potent antagonist of barbiturates in the central nervous system

Our previous study indicated that picrotoxin competes with phenobarbital (PB) for the binding to liver microsomes, although the target of binding and the physiological role were not determined (unpublished observation). To seek information on the target site of PB, reflecting the induction of hepatic enzymes, we examined here the effect of picrotoxin on PB-mediated induction of hepatic cytochrome P450 and UDP-glucuronosyltransferase in vivo in rats. The induction of the CYP2B1/2 was estimated by immunoblot analysis and by measuring the activity of testosterone 16beta-hydroxylation. Intraperitoneal injection of picrotoxin alone slightly increased CYP2B1/2 protein. An experiment on co-treatment of picrotoxin and PB showed that picrotoxin enhanced rather than antagonized the inducing effect of PB. The results suggest two possibilities: that 1) picrotoxin increases the CYP2B subfamily by binding to the same site as PB; or 2) the site in microsomes for the competition between PB and picrotoxin does not reflect the induction of P450.

Activation of macrophages by crude polysaccharide fractions obtained from shoots of Glycyrrhiza glabra and hairy roots of Glycyrrhiza uralensis in vitro

Many plant polysaccharide fractions have been reported as immunomodulatory agents. However, sometimes the possibility of contamination with bacterial lipopolysaccharide (LPS), a potent B cell mitogen and immune modulator, is discussed. In the present paper, we investigated the effects of crude polysaccharide fractions obtained from the shoot and hairy root of Glycyrrhizae sp. on murine peritoneal macrophage function, in order to clarify whether plants grown under aseptic conditions produce immunomodulatory polysaccharides. All crude polysaccharide fractions induced nitric oxide production by murine peritoneal macrophages in vitro. Chemical analysis revealed that LPS-like molecules were not present in all preparations. These results suggested that shoot and hairy root biosynthesized polysaccharides that could stimulate macrophages de novo.

Metabolism of 2,3',4',5-tetrachlorobiphenyl by cytochrome P450 from rats, guinea pigs and hamsters

The metabolism of 2,3',4',5-tetrachlorobiphenyl (TCB) was compared using liver microsomes and six isoforms of cytochrome P450 purified from rats, guinea pigs and hamsters. In microsomal study, the following species differences were observed: 1) Untreated guinea pigs and hamsters but not rats can metabolize this TCB to 3-hydroxy- or 4-hydroxy-2,3',4',5-TCB, 2) Guinea pig microsomes showed only 3-hydroxylating activity, whereas hamster microsomes showed higher activity of 4-hydroxylation than that of 3-hydroxylation. In common with three species, the 3-hydroxylation was accelerated by phenobarbital. The 4-hydroxylation in rats and hamsters was increased by pretreatment with 3-methylcholanthrene and 3,3',4,4',5-pentachlorobiphenyl. The hydroxylation activities of liver microsomes from the three species could be explained by an involvement of different isoforms of cytochrome P450. In addition, it is apparent that hamster CYP1A2 as well as hamster CYP2A8 is involved in the 4-hydroxylation of 2,3',4',5-TCB although it has no activity for 2,2',5,5'-TCB.

A new screening method for amphetamine and methamphetamine using dansyl chloride derivatization and cartridge fluorescence

A new screening method for amphetamines was developed. It consists of derivatization with dansyl chloride, extraction of the derivative using a Sep-Pak C18 or a Bond Elut C18, solid phase extraction columns, and visualization of the fluorescence of the cartridge. A control test using drug-free urine showed no fluorescence. Amphetamine, methamphetamine and the methylenedioxy derivatives exhibited strong fluorescence, while related compounds, such as N-ethylamphetamine and fenetylline, were negative or weakly positive. The disadvantage of the present method is that it is a multi-step procedure and 20-30 min is required for screening. However, since it has a different specificity from the widely used immunochemical technique, it is suggested to be a useful screen for amphetamines.

Highly toxic coplanar PCB126 reduces liver peroxisomal enzyme activities in rats

The effect of the highly toxic coplanar PCB congener, 3,4,5,3',4'-pentachlorobiphenyl (PCB126) on hepatic peroxisomes was studied in rats. The aim of this study was to investigate whether a toxic dose of the dioxin-like coplanar PCB modifies enzyme activities in peroxisomes where plays an important role in lipid metabolism. Treatment with PCB126, at a single i.p. administration of 25 mg/kg which evokes clear suppression of body weight gain, resulted in marked reduction (to about 40-50%) of catalase activity and peroxisomal fatty acyl-CoA β-oxidizing system. Immunoblotting showed that expression of catalase was greatly reduced by the treatment in parallel with the activity. Light microscopy revealed a drastic reduction in granules possessing peroxidase activity, while electron microscopy demonstrated that no apparent morphological changes had taken place. Thus the reduction in catalase activity caused by PCB126 could be attributable to suppression of protein expression. The marked reduction of these peroxisomal enzyme activities might be related to hyperlipidemia caused by dioxin-related compounds in rats and humans.

Induction of rat hepatic cytochrome P450 2B subfamily by azidophenobarbital, as a possible photoaffinity probe for the putative phenobarbital receptor: comparative study with modified phenobarbitals with different functional groups

To study the specific target to which phenobarbital (PB) binds, resulting in the induction of cytochrome P450, we prepared two azido-PBs (AZPBs) as photoaffinity ligands. The azido substituent was introduced at the para- or meta-position of the PB aromatic ring. In this study, we estimated the utility of these compounds by examining their inducing activities in vivo in rats. Induction was assessed by immunoblotting with anti-CYP2B1/2 antibody and measuring testosterone-metabolizing activity, using hepatic microsomes. Administration of p-AZPB to rats increased hepatic CYP2B1/2 protein and testosterone 16beta-hydroxylase activity, although the effects were less than those of unmodified PB. m-AZPB showed no effect in the induction of CYP2B1/2. To assess the specificity of the effects of substituents, we compared the inducing activities of p/m-nitro-PBs, p/m-amino-PBs, and p/m-hydroxy-PBs with those of AZPBs. The results showed that p-nitro-PB, m-amino-PB, and p-hydroxy-PB were also potent inducers for CYP2B1/2, with lower activity than that of unmodified PB, whereas the other three isomers had no effect. These results suggest that 1) the absence of any substituents on the aromatic ring of PB is needed for maximal inducing activity and 2) substitution at the meta-position of the PB aromatic ring tends to reduce effectiveness as an inducer more than does substitution at the para-position. Because p-amino-PB and p-acetylamino-PB, the minor and major metabolites of p-AZPB, respectively, were without effect in the induction of CYP2B1/2, the effect of p-AZPB was considered to be due to the unchanged compound itself. The present study demonstrates that, based on the weak but positive ability to induce CYP2B1/2, p-AZPB may be a useful tool for identifying the putative PB receptor.

Metabolism of 2,4,5,2',4',5'-hexachlorobiphenyl (PCB153) in guinea pig

1. The in vitro and in vivo metabolism of 2,4,5,2',4',5'-hexachlorobiphenyl (PCB153) in guinea pig has been studied. 2. Seven metabolites were detected in the faeces of PCB153-treated animals and three were identical to those produced by dog liver microsomes. The detection of a metabolite where a chlorine atom was shifted from the 2- to 3-position strongly suggested the involvement of 2,3-arene oxide intermediate, and evidence for the concomitant formation of a 3,4-arene oxide intermediate was provided by identifying other two minor metabolites which were dechlorinated at the 4-position. 3. In vitro studies using liver microsomes from guinea pigs revealed that the 2,3-arene oxide and 3-hydroxylation pathways are the predominant metabolic routes compared with the 3,4-arene oxide pathway. Although the guinea pig is an another species that can metabolize PCB153 mainly to the 2,3-arene oxide intermediate, the rate of formation was only about one-tenth of the dog. 4. These results indicate that the ability to form this unusual 2,3-arene oxide intermediate may not be responsible for high excretion rate of this congener. Our data also suggest that the cytochrome P450-catalysed metabolism of PCB153 in the guinea pig and dog are similar, whereas for post-cytochrome P450 metabolism, the guinea pig resembles the rabbit.

Species-specific alteration of hepatic glucose 6-phosphate dehydrogenase activity with coplanar polychlorinated biphenyl: evidence for an Ah-receptor-linked mechanism

We examined the in vivo effect of a highly toxic coplanar polychlorinated biphenyl (PCB) on the hepatic activity of glucose 6-phosphate dehydrogenase (G6PDH) in aryl hydrocarbon (Ah)-responsive (C57/BL) and -less-responsive (DBA) strains of mice. The activity in the C57BL strain was moderately increased by 3,3',4,4',5-pentachlorobiphenyl (PCB 126) in a dose dependent manner. However, this was not observed in DBA mice although greater doses were injected. 2,2',5,5'-Tetrachlorobiphenyl (PCB 52) with a non-planar structure did not increase G6PDH activity. The increase in G6PDH activity with PCB 126 was also seen in rats, but not in guinea pigs. The activity in the latter species was decreased rather than increased. These results suggest that the induction of hepatic G6PDH by coplanar PCB is mediated by a mechanism involving the Ah receptor, and the response was highly species-specific.

Changes in the hepatic glutathione peroxidase redox system produced by coplanar polychlorinated biphenyls in Ah-responsive and -less-responsive strains of mice: mechanism and implications for toxicity

The alteration in hepatic glutathione peroxidase (GPx) produced by polychlorinated biphenyls (PCBs) was studied in vivo in aryl hydrocarbon (Ah)-responsive C57BL and -less-responsive DBA strains of mice. 3,3',4,4',5-Pentachlorobiphenyl (PCB 126), one of the high-affinity ligands for the Ah receptor, significantly reduced Se-dependent GPx activity in C57BL mice, but not in DBA mice. A reduction in activity in C57BL mice was also observed following treatment with a high dose of 3,3',4,4'-tetrachlorobiphenyl with lesser affinity for the Ah receptor than PCB 126, but not by 2,2',5,5'-tetrachlorobiphenyl, a low-affinity ligand. To assess the effects on GPx in the liver, the content of reduced glutathione (GSH), an obligate co-factor for GPx, and the activity of two enzymes, γ-glutamyl transpeptidase (γ-GTP) and glutathione reductase (GR), which play a role in supplying GSH were determined after PCB treatment. The results showed that although the hepatic activity of γ-GTP and GR was affected differently by PCB 126, the content of GSH was slightly increased rather than reduced in both strains of mice. The activity of non-Se-dependent GPx, which is due to the catalysis by some isozymes of glutathione S-transferase (GST), was significantly increased only in C57BL mice by PCB 126 treatment. Immunoblot analysis demonstrated that the induction of the class θ GST, which is a potent reducer of peroxides (Hiratsuka et al., 1995. Biochem. Biophys. Res. Commun. 212, 743) reflects the enhancement of the above activity. These results suggest that (i) the PCB-induced reduction in Se-dependent GPx activity is mediated by a mechanism involving the Ah receptor; and (ii) a concomitant increase in the class θ GST partially rescues the Ah-responsive mice from coplanar PCB-induced oxidative stress.

[Production of antibody against cytosolic 54 kDa protein in rat liver--evidence of the significant induction by a highly toxic coplanar polychlorinated biphenyl]

We have reported that a 54 kDa protein in rat liver cytosol is highly inducible by treatment with 3,3',4,4',5-pentachlorobiphenyl (PenCB) or 3-methylcholanthrene (MC) using SDS-polyacrylamide gel electrophoresis. Internal amino acid sequences of this protein in the rat liver were highly homologous to those of selenium binding protein (SeBP) or acetaminophen binding protein (APBP) in mouse liver cytosol. In this paper, the purification and characterization of this protein were demonstrated. MC was given at a dose of 20 mg/kg for 3 consecutive days. The liver cytosolic 54 kDa protein was purified twice from the MC-treated male Wistar rats by Rotofore Cell procedure to apparent single on SDS-polyacrylamide gel electrophoresis, and the rabbit antiserum against this protein was obtained. Male Wistar rats were given PenCB in corn oil at a single dose of 25 mg/kg i.p. The liver cytosol was prepared on the 5th day after the treatment and subjected to immunoblot analysis. The 54 kDa protein was markedly induced in the liver cytosol of PenCB-treated rats. Immunoblot analysis after two-dimensional gel electrophoresis suggested that there could be isoforms of 54 kDa protein. The induction of the 54 kDa protein with PenCB was assumed to be mediated through Ah-receptor. The physiological role of the 54 kDa protein was discussed together with SeBP and APBP, the role of which has not yet been elucidated.

[Effect of co-planar polychlorinated biphenyl on the hepatic glutathione peroxidase redox system in rats and guinea pigs]

The effect of 3,3',4,4',5-pentachlorobiphenyl (PCB 126) on hepatic glutathione peroxidase (GPx) redox system was studied in vivo in rats and guinea pigs. PCB 126 treatment caused significant reduction of Se-dependent and -non-dependent GPx activity in rats. In agreement with this, the content of glutathione (GSH) and the activities of GSH reductase (GR) and gamma-glutamyl transpeptidase (gamma-GTP) were also decreased in this species. On the contrary, guinea pig liver Se-non-dependent GPx activity was significantly enhanced by PCB 126 treatment, while no effect on Se-dependent activity was observed. Neither the content of GSH nor the enzyme activities responsible for GSH supply in guinea pig liver was affected by PCB 126. These result suggested that the damage on GPx redox system is, at least, one of mechanisms by which co-planar PCB induces the toxicity in rats. However, in guinea pigs, this is not the case, and different mechanism from the damage on active oxygen quenching system is likely to be involved.

A highly toxic PCB produces unusual changes in the fatty acid composition of rat liver

The changes in lipid metabolism produced by a coplanar PCB were studied in rats. Male Wistar rats were given a single intraperitoneal injection of 3,3',4,4',5-pentachlorobiphenyl at a dose of 25 mg/kg. After 5 days of administration, total hepatic lipids were treated with 1 M KOH in methanol at 75 degrees C and the liberated fatty acids were analyzed by HPLC after conversion to fluorescent derivatives. In comparison with free-fed and pair-fed control groups, the proportion of arachidonic acid in the PenCB-treated rats was reduced by about 50%, while oleic and linoleic acids increased significantly. We also examined the individual glycerophospholipids, separated by TLC, to see if they were affected by alteration in the fatty acid composition of the whole liver. In all glycerophospholipids, the proportion of arachidonic acid was reduced significantly to the same degree while linoleic acid increased. Changes in the activity of desaturase isozymes have been postulated to explain this unusual lipid metabolism following administration of a toxic PCB and this may contribute to its toxicity.

Major role of the CYP2C isozymes in deamination of amphetamine and benzphetamine: evidence for the quinidine-specific inhibition of the reactions catalysed by rabbit enzyme

1. The cytochrome P450 isozymes involved in the deamination of amphetamine (AP) and benzphetamine (BZP) have been studied in liver microsomes from rabbit and rat using isozyme-specific inhibitors. 2. Metabolism of BZP in rat yielding phenylacetone and formaldehyde was moderately inhibited by testosterone and chloramphenicol. N-Debenzylation was thought to be P450-dependent, but all inhibitors except for a non-specific inhibitor, SKF-525A, failed to inhibit this reaction. 3. In rabbit, quinidine and testosterone were potent inhibitors of both BZP deamination and dealkylation. Deamination of AP in rabbit was extensively inhibited only with quinidine. 4. AP deamination with purified rabbit CYP2C3, which was previously identified as the major isozyme responsible for this metabolism, was extensively inhibited with quinidine, previously thought to be a specific inhibitor of CYP2D. 5. These results strongly support the notion that the CYP2C isozymes play a major role in the deamination of both AP and BZP, but not for N-debenzylation of BZP in rat. However, on the basis of different sensitivities toward inhibitors, multiple isozymes seem to be involved in BZP deaminations in both species.

Induction of two UDP-glucuronosyltransferase isoforms sensitive to phenobarbital that are involved in morphine glucuronidation: production of isoform-selective antipeptide antibodies toward UGT1.1r and UGT2B1

We document here in that two UDP-glucuronosyltransferase (UGT) isoforms sensitive to phenobarbital are involved in morphine glucuronidation in Wistar and Sprague-Dawley rats. The hepatic microsomal morphine UGT activity in untreated Gunn rats was significantly less than that of untreated Wistar rats. Although the morphine UGT activity in the liver of Gunn rats was increased by phenobarbital (PB) treatment, this was significantly less than that in the liver of PB-treated Wistar rats. UGT1.1r is an isoform of morphine UGT in rat, and UGT2B1 is also considered an isoform of morphine UGT, because UGT2B1 (stably expressed in V79 cells) exhibited morphine UGT activity. We prepared specific antipeptide antibodies against UGT1.1r and UGT2B1. Using isoform-specific antipeptide antibodies, both UGT1.1r and UGT2B1 in Wistar and Sprague-Dawley rats were inducible by PB treatment. However, UGT1.1r is not present in the liver from Gunn rats. This study is the first demonstration that protein levels of two morphine UGT isoforms, UGT1.1r and UGT2B1, in the liver of Wistar and Sprague-Dawley rats are inducible by PB treatment.

Deamination of amphetamines by cytochromes P450: studies on substrate specificity and regioselectivity with microsomes and purified CYP2C subfamily isozymes

Deamination or oxidative cleavage of the carbon-nitrogen bond in various phenylisopropylamines was examined in liver microsomes from rabbits and rats, and in reconstituted systems containing CYP2C subfamily isozymes. Kinetic studies of phenylacetone formation from six amphetamine (AP) derivatives, catalyzed by rabbit liver microsomes, indicated that AP had the highest apparent affinity (lowest K(m)) and increasing the size of the substituent on the nitrogen atom decreased the affinity. The values of maximal velocity increased with increasing size of the substituent. Experiments with purified CYP2C3 from rabbit liver gave similar results: this enzyme showed the highest activity for phenylacetone formation from benzphetamine (BZP) and showed lower activities with compounds having smaller nitrogen substituents. Based on these results, we conclude that among a series of AP derivatives, the parent phenylisopropylamine has the highest affinity for rabbit liver deaminase, where as BZP has the highest turnover. However, the intrinsic clearance (Vmax/K(m)) values for the individual reactions tended to be comparable. The rates of BZP and deprenyl N-demethylation by rat CYP2C11 and 2C13 were far greater than those of the reactions at other N-alpha-positions. This result indicated that rat CYP2C enzymes have a more rigid regioselectivity than rabbit CYP2C3 for the deamination/N-dealkylation of phenylisopropylamines.

Significant suppression of rat liver aldolase B by a toxic coplanar polychlorinated biphenyl, 3,3',4,4',5-pentachlorobiphenyl

A toxic coplanar polychlorinated biphenyl, 3,3',4,4',5-pentachlorobiphenyl (PenCB), significantly suppresses the expression of liver aldolase B in rats. Hepatic aldolase activity in PenCB-treated rats was significantly reduced to about 50% of that in free- and pair-fed control groups. The reduced aldolase activity following PenCB-treatment was due to the marked suppression of the expression of aldolase B shown by immunoblot analysis after SDS-polyacrylamide gel electrophoresis and two-dimensional gel electrophoresis. The suppression of rat liver aldolase B could be a key biochemical lesion caused by PenCB.

Significant induction of a 54-kDa protein in rat liver with homologous alignment to mouse selenium binding protein by a coplanar polychlorinated biphenyl, 3,4,5,3',4'-pentachlorobiphenyl and 3-methylcholanthrene

A 54-kDa protein in rat liver cytosol was significantly induced by treatment with 3,4,5,3',4'-pentachlorobiphenyl (25 mg/kg, single i.p.) and 3-methylcholanthrene (20 mg/kg, once a day for 3 days, i.p.). The protein exhibited pI of 6.8 on two-dimensional gel electrophoresis. The amino acid sequences of peptide fragments from the protein digested in situ were highly similar to a selenium binding protein in mice and to the isoform acetaminophen binding protein in mice. The present result clearly demonstrates that a coplanar polychlorinated biphenyl and 3-methylcholanthrene are responsible for induction of selenium binding protein homologues. The physiological role of the mouse proteins, however, is not yet elucidated.

Hamster liver cytochrome P450 (CYP2A8) as a 4-hydroxylase for 2,5,2',5'-tetrachlorobiphenyl

Metabolism of 2,5,2',5'-tetrachlorobiphenyl (TCB) was studied using liver microsomes of hamsters and two hamster P450 isoforms, CYP1A2 and 2A8. CYP2A8 catalyzed selectively 4-hydroxylation of 2,5,2',5-TCB at a rate of 21.7 pmol/min/nmol P450. In contrast, CYP1A2 showed no activity for hydroxylation of 2,5,2',5'-TCB. Immunological study revealed that rabbit antiserum against CYP2A8 almost completely inhibited the microsomal 4-hydroxylation but that against CYP1A2 did not. It was also shown that the induction pattern of CYP2A8 protein by P450 inducer was similar to that of the 4-hydroxylase activity in hamster liver microsomes. These results suggest that CYP2A8 plays a major role in the 4-hydroxylation of 2,5,2',5'-TCB in hamster liver.

Phosphorylation of a membrane-intercalated proteoglycan, syndecan-2, expressed in a stroma-inducing clone from a mouse Lewis lung carcinoma

We previously reported that a mouse Lewis lung carcinoma-derived stroma-inducing clone, P29, highly expresses a syndecan-like proteoglycan exhibiting specific binding to fibronectin, a major constituent of the interstitial matrix formed by the induced stromal cells, via its heparan sulphate chains [Itano, Oguri, Nakanishi and Okayama (1993) J. Biochem. (Tokyo) 114, 862-873]. On metabolic labelling of the proteoglycan with [32P]Pi, followed by identification of the radiolabelled material using glycanases, almost all the isotope was found to have been incorporated into a core portion of molecular mass 48 kDa, which was generated by digestion with heparan sulphate lyase I plus chondroitin ABC lyase. Immunoblotting of the core protein with a monoclonal antibody, F58-6G12, demonstrated that the proteoglycan was mouse syndecan-2. CsCl-density-gradient centrifugation after mild treatment of liposome-intercalated 32P-labelled syndecan-2 with trypsin resulted in clear separation of the radioactivity into a bottom fraction containing all the glycosaminoglycans (accounting for 40% of the total radioactivity) and a top fraction containing liposome-associated peptides (60%). The former isotope was shown to be linked covalently to both heparan sulphate and chondroitin sulphate chains, probably at their bridge regions. The latter was mostly attributed to phosphoserine, the one and only phosphorylated amino acid released on acid hydrolysis of this proteoglycan, strongly suggesting that the phosphorylation occurs at a specific serine residue(s) in the cytoplasmic domain of the core protein.

Role of cytochrome b5 in the oxidative metabolism of polychlorinated biphenyls catalyzed by cytochrome P450

1. The role of cytochrome b5 in the cytochrome P450-dependent hydroxylation of tetrachlorobiphenyl (TCB) isomers was examined using a reconstituted system consisting of CYP2B1 and CYP1A1 and rat liver microsomes. 2. By addition of cytochrome b5 to the reconstituted system containing CYP2B1, the 3-hydroxylation of 2,5,2,'5'- and 2,5,3',4'-TCB was increased about six-fold, but the 3- and 5-hydroxylation of 2,4,3',4'-TCB was decreased by about 50% 3. All hydroxylations of 3 ,4,3',4'-,2,5, 3,4'- and 2,4,3',4'-TCBs were decreased by addition of cytochrome b5 to the reconstituted system containing CYPlA1. 4. In stoichiometry measurements, changes in NADPH oxidation and coupling efficiency by addition of cytochrome b5 was observed and these differed according to the position of chlorine atoms of TCBs and cytochrome P450 isoforms used in the systems.

A coplanar PCB induces a selenium binding protein as a major cytosolic protein in rat liver

We obtained evidence that a toxic coplanar polychlorinated biphenyl (PCB) induces a counterpart of murine 56kDa selenium binding protein in rat liver cytosol. A 54kDa protein in the liver cytosol was significantly induced by 3,3',4,4',5-pentachlorobiphenyl and proved to be a major cytosolic protein in the rat liver. The protein exhibited pI of 6.8 on two-dimensional gel electrophoresis. The amino acid sequence of peptide fragments from the protein digested in situ, was highly similar to a 56kDa selenium binding protein and similar to an acetaminophen binding protein in mice.

Brucine as a potent inducer of CYP2B3, the third member of the CYP2B subfamily P450 in rats

We have indicated that strychnine and brucine induce concurrently an unknown P450 (2B-UP) which cross-reacts with anti-CYP2B1 antibody (Fujisaki et al., J. Pharmacol. Exp. Ther., 268, 1024-1031, 1994). We purified 2B-UP from brucine-treated rats and characterized it in this study. The purification was achieved by solubilization with sodium cholate followed by successive chromatographic steps with omega-aminooctyl-Sepharose 4B, DEAE-Sephacel and hydroxyapatite. The minimum molecular weight of purified 2B-UP was calculated to be 48000 by sodium dodecyl sulfate-gel electrophoresis. This preparation showed no Soret peak in the ultraviolet absorption spectrum indicating absence of heme. The amino terminal sequence of 2B-UP up to the 10th residue was consistent with the deduced amino acid sequence of CYP2B3 cDNA, but did not agree with the sequences of CYP2B1/2. The result strongly suggests that 2B-UP is CYP2B3. Thus, we indicated here that Strychnos alkaloid, brucine, is a potent inducer of the CYP2B3 or the closely related P450.

Involvement of cytochrome b5 in the metabolism of tetrachlorobiphenyls catalyzed by CYP2B1 and CYP1A1

The role of cytochrome b5 in the cytochrome P450 (CYP)-dependent hydroxylation of tetrachlorobiphenyl (TCB) isomers was examined using a reconstituted mixed function oxygenase (MFO) system containing purified CYP2B1 or 1A1, and rat liver microsomes. Hydroxylations of 2,2',5,5'- and 3,3',4,4'-TCBs were catalyzed mainly by CYP2B1 and 1A1, respectively, in the reconstituted MFO system and those of 2,3',4',5- and 2,3',4,4'-TCBs were mediated by both cytochrome P450 systems. The activity toward 2,2',5,5'- and 2,3',4',5-TCB was significantly increased 6.5- and 5.5-fold, respectively, by addition of cytochrome b5 in the reconstituted MFO system containing of CYP2B1. Either hydroxylation activity toward 2,3',4,4'-TCB with the CYP2B1 system was very low or decreased by addition of cytochrome b5. These results suggest that the involvement of cytochrome b5 to the hydroxylation of TCBs is dependent on the TCB congener being metabolized, and the cytochrome P450 isoform involved in its metabolism.

Purification of a phenobarbital-inducible UDP-glucuronosyltransferase isoform from dog liver which catalyzes morphine and testosterone glucuronidation

A morphine UDP-glucuronosyltransferase (UGT) which could belong to the UGT2B subfamily was isolated from liver microsomes of a male beagle dog treated with phenobarbital. Glucuronidation toward morphine in the dog liver microsomes was increased threefold by the treatment. The microsomes were solubilized with Emulgen 911 and applied on a column of hemisuccinate derivative of Sepharose 4B column which has been developed in our laboratory. An isoform of UGT in the eluate was purified further by chromatofocusing and UDP-hexanolamine-affinity chromatography. A purified enzyme, UGTDOG-PB, was homogeneous on sodium dodecyl sulfate polyacrylamide gel electrophoresis and two-dimensional electrophoresis and exhibited a subunit molecular weight of 50 kDa. This isoform showed activities toward the 3-hydroxyl group of morphine, 4-hydroxybiphenyl, 4-nitrophenol, 4-methylumbelliferone, and testosterone, but not toward chloramphenicol and the 6-hydroxyl group of morphine. The substrate specificity of UGTDOG-PB is similar to that of stably expressed UGT2B1 which is considered a phenobarbital-inducible morphine UGT in the rat except that UGTDOG-PB is capable of glucuronidating 4-nitrophenol but not chloramphenicol. The NH2-terminus until the 30th residue of UGTDOG-PB is highly homologous to UGT2B subfamily, and the NH2-terminal 15 residues of UGTDOG-PB are completely identical to those of UGT2B1, UGT2B8, and UGT2B15. This is the first report describing the UGT isoform of dog and the purification of morphine UGT which may belong to UGT2B subfamily.

Metabolism of highly persistent PCB congener, 2,4,5,2',4',5'-hexachlorobiphenyl, by human CYP2B6

Metabolism of 2,4,5,2',4',5'-hexachlorobiphenyl was studied with cDNA-expressed human P450 2B isoform, CYP2B6. 3-Hydroxy-2,4,5,2',4',5'-hexachlorobiphenyl was identified as a major metabolite, and the formation activity was compared with that of dog CYP2B11 and guinea pig P450GP-1. The activity of 3-hydroxylation was comparable with that of P450GP-1, but one-tenth of CYP2B11. These results indicate that P450 2B in humans as well as other animal species can metabolize 2,4,5,2',4',5'-hexachlorobiphenyl, and the reason why this PCB congener remained most abundantly in human bodies is discussed.

[Alteration of peroxisomal enzyme activities in the liver of guinea pigs caused by coplanar PCB]

The hyperlipidemia is a well-known typical symptom in Yusho patients and experimental animals treated with PCBs. We have found a significant induction of CYP4A1, which catalyzes omega-hydroxylation of fatty acids, in guinea pigs by the treatment with a coplanar PCB, 3, 4, 5, 3',4-pentachlorobiphenyl (PenCB), though the P450 is reduced in the treated rats. Peroxisome has beta-oxidation enzymes distinct from mitochondrial enzymes, and also play an important role in lipid metabolism. Peroxisome proliferators have been shown to regulate the expression of CYP4A1 and peroxisomal enzymes by the same mechanism in the rat. In the present study, we examine the effect of PenCB treatment on peroxisomal enzymes in the liver of guinea pigs. As a result, the enzyme activities of hepatic peroxisome, e.g. fatty acid oxidizing system, catalase and urate oxidase, had a rising tendency by the treatment with PenCB in the animal. The results suggest that the regulation of peroxisomal enzymes and CYP4A1 is also associated in guinea pigs, and PenCB provides a similar effect of peroxisomal proliferators to the animal. The possible toxicity through the peroxisomal alteration was discussed.