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R J Edwards

Publications and source records attributed to R J Edwards.

At least 55 records · Page 3Linked to original sources
PubMed1999

Interaction of the transactivating protein HIV-1 tat with sulphated polysaccharides.

Endogenous sulphated polysaccharides such as heparin have been shown to inhibit the infectivity of HIV-1 min vitro. However, these naturally occurring polymers, due to extensive microheterogeneity within their structure, are difficult to characterise accurately. In contrast, dextrin can be chemically sulphated to produce a series of compounds sulphated in the 2-, 3-, or 6- position, or in all 3 positions, and the use of these compounds provides an opportunity to investigate the anti-HIV-1 activity of sulphated polysaccharides. The mechanisms whereby sulphated polysaccharides exert their anti-HIV-1 activity have not been fully elucidated. The interaction of recombinant HIV-1 proteins with sulphated polysaccharides was investigated using a biotinylated derivative of dextrin 2-sulphate (D2S) in a solid phase binding system. D2S was found to bind strongly to HIV-1 tat (EC50 = 0.10 microg/mL), less strongly to CD4 (EC50 = 0.33 microg/mL), weakly to HIV-1 vif and gp160, and not at all to HIV-1 gp120 or p24. Other sulphated derivatives of dextrin, i.e. dextrin 3-sulphate, dextrin 6-sulphate and dextrin 2,3,6-trisulphate, as well as heparin and dextran sulphate, were also shown to bind to HIV-1 tat, whereas the unsulphated compound dextrin did not. Binding studies using a series of overlapping peptides representing the complete sequence of HIV-1 tat revealed that D2S bound most strongly to the core domain of HIV-1 tat, although there was also binding to the cysteine-rich domain; both of these regions are important for HIV-1 tat function. In assessing function, HIV-1 tat-mediated transactivation was measured using H938 cells, a cell line that contains the HIV-LTR (long terminal repeat) promoter linked to a chloramphenicol acetyltransferase gene. D2S significantly inhibited HIV-1 tat transactivation in a dose-dependent manner (IC50 = 0.5 microg/mL), whereas dextrin had no effect. The interaction between D2S and HIV-1 tat provides a potential mechanism of HIV-1 inhibition whereby tat is sequestered and its transactivating activity abolished, effectively inhibiting the replication cycle.

Amino Acid Sequence↗
PubMed1999

Expression and localisation of CYP2D enzymes in rat basal ganglia.

P450 enzymes in the CYP2D subfamily have been suggested to contribute to the susceptibility of individuals in developing Parkinson's disease. We have used specific anti-peptide antisera and peroxidase immunohistochemistry to investigate the expression of CYP2D enzymes in the rat brain and some possible factors that may affect their regulation. In male Wistar rats, CYP2D1 was not detected in the basal ganglia or in any other brain region. CYP2D2 was weakly expressed within neurones of the subthalamic nucleus, substantia nigra and interpeduncular nucleus as well as in the hippocampus, dentate gyrus, red nucleus and pontine nucleus. CYP2D3 and CYP2D4 were absent from the basal ganglia, although moderate amounts of CYP2D3 were detected within fibres of the oculomotor root, and very low levels of CYP2D4 were present in white matter tracts. In contrast, CYP2D5 was extensively expressed in the basal ganglia, including neurones in the subthalamic nucleus, substantia nigra and interpeduncular nucleus, as well as other areas of the brain, including the ventral tegmental area, piriform cortex, hippocampus, dentate gyrus, medial habenular nucleus, thalamic nucleus and pontine nucleus. Lesioning of the nigro-striatal tract to cause almost a complete loss of tyrosine hydroxylase containing neurones in the substantia nigra, also reduced the number of neurones expressing CYP2D5 by 50%, indicating that CYP2D5 is expressed in dopaminergic neurones. Castration of pre-pubertal or adult Wistar rats had no effect on the number of CYP2D5-positive neurones in the substantia nigra. Although Dark Agouti rats lack hepatic CYP2D2, expression in the midbrain was similar to that of Wistar rats; furthermore, there was no difference in expression or distribution between male and female rats. In contrast to naive rats, extensive expression of CYP2D4 was found throughout the basal ganglia and in other brain nuclei in Wistar rats treated with not only clozapine, but also saline, suggesting that CYP2D4 may be induced as a result of mild stress. The function of CYP2D enzymes in the brain remains unknown, but their selective localisation suggests a physiological role in neuronal activity and in adaptation to abnormal situations.

Animals↗
PubMed1999

Resistance of three immortalized human hepatocyte cell lines to acetaminophen and N-acetyl-p-benzoquinoneimine toxicity.

BACKGROUND/AIMS: Acetaminophen toxicity in hepatocytes is attributed to generation of the toxic metabolite N-acetyl-p-benzoquinoneimine, leading to depletion of intracellular glutathione, alteration of redox potential and ultimately, cellular necrosis. We aimed to determine the effect of acetaminophen and N-acetyl-p-benzoquinoneimine on three human hepatocyte cell lines HH25, HH29 and HHY41, and for comparison, on primary rat hepatocytes, a cell type that is relatively resistant to acetaminophen-induced toxicity. METHODS: We investigated the effect of incubation of rat hepatocytes and 3 hepatocyte cell lines with acetaminophen or N-acetyl-p-benzoquinoneimine on LDH release, glutathione status, mitochondrial function, CYP1A activity, albumin synthesis and DNA content. RESULTS: We demonstrated that HH25, HH29 and HHY41 are resistant to the toxic effects of acetaminophen under conditions that induce cytotoxicity in rat primary hepatocytes, as indicated by maintenance of glutathione levels and basal LDH release. Incubation with N-acetyl-p-benzoquinoneimine caused a dose-dependent cytotoxicity in rat hepatocytes. Under comparable conditions N-acetyl-p-benzoquinoneimine had no effect on any of the hepatocyte cell lines. Nevertheless, when culturing the cells for a further 48 h, a decrease in glutathione levels, albumin synthesis, CYP1A activity, DNA content and mitochondrial function was apparent. CONCLUSION: HH25, HH29 and HHY41 cells are highly resistant to acetaminophen and N-acetyl-p-benzoquinoneimine-induced toxicity. They tolerate a much higher concentration of both toxins for a longer period of time compared to rat primary hepatocytes. These results are of relevance in the use of these cell lines to investigate acetaminophen hepatotoxicity, and may be of importance in the choice of cells for use in bioartificial liver support systems.

Acetaminophen↗
PubMed1999

Expression of xenobiotic-metabolizing CYPs in human pulmonary tissue.

The pattern of expression of individual cytochrome P450 (CYP) forms participating in the metabolism of xenobiotics is being increasingly well characterised in the human pulmonary tissue. Recent studies using methods having increased sensitivity and specificity, such as the reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, have revealed constitutive and inducible expression of several CYP forms in different cell types of the human lung. These studies have revealed the presence of mRNA of several procarcinogen-activating CYP forms in whole lung tissue and alveolar macrophages, including CYP1A1, CYP2B6/7, CYP2E1, and CYP3A5. The results of several studies on CYP2D6 expression have yielded contradictory results. Immunohistochemical analysis shows that CYP3A5 protein is present in all lung samples studied, and is localized in the ciliated and mucous cells of the bronchial wall, bronchial glands, bronchiolar ciliated and terminal cuboidal epithelium, type I and type II alveolar epithelium, vascular and capillary endothelium, and alveolar macrophages. Also CYP3A4 protein is found in some cell types in a minority (about 20%) of lung samples. Primary cultures of freshly isolated broncho-alveolar macrophages as well as a continuously growing bronchial carcinoma cell line (A-549) are being used for CYP induction studies in our laboratory. The results indicate that CYP1 family members are inducible in these cells by polycyclic aromatic hydrocarbon (PAH) inducers, and that CYP3A5, but not CYP3A4, is present constitutively. The results of these studies indicate that several different xenobiotic-metabolizing CYPs are present in the human lung and lung-derived cell lines, possibly contributing to in situ activation of pulmonary procarcinogens. Interindividual differences in the expression of these CYPs may contribute to the risk of developing lung cancer and possibly other pulmonary diseases initiated by agents that require metabolic activation.

Cells, Cultured↗
PubMed1999

A Rad3-Rad26 complex responds to DNA damage independently of other checkpoint proteins.

The conserved PIK-related kinase Rad3 is required for all DNA-integrity-checkpoint responses in fission yeast. Here we report a stable association between Rad3 and Rad26 in soluble protein extracts. Rad26 shows Rad3-dependent phosphorylation after DNA damage. Unlike phosphorylation of Hus1, Crb2/Rhp9, Cds1 and Chk1, phosphorylation of Rad26 does not require other known checkpoint proteins. Rad26 phosphorylation is the first biochemical marker of Rad3 function, indicating that Rad3-related checkpoint kinases may have a direct role in DNA-damage recognition.

Adenosine Triphosphatases↗
PubMed1999

The mutagenicity of benzo[a]pyrene in mouse small intestine.

We have investigated the mutagenicity of benzo[a]pyrene (B[a]P) in small intestine using the Dlb-1 locus assay in the mouse. Administration of B[a]P by the oral and i.p. routes had markedly different effects on the number of Dlb-I mutations and the pattern of induction of cytochrome P-4501A1 (CYP1A1). In Ahr-responsive animals i.p. injection resulted in marked induction in crypt cells along the length of the small intestine, with some induction in the villus cells. In contrast, after oral administration, CYP1A1 induction was evident only in the villus cells, and this declined distally. The intensity and speed of induction in Ahr-responsive animals was such that the genotoxic effect of a single injection of B[a]P could not be augmented by prior treatment with non-genotoxic inducers such as beta-napthoflavone and TCDD. Oral B[a]P treatment resulted in a decrease in the number of mutations when compared with the i.p. route. Studies in congenic Ahr-non-responsive versus Ahr-responsive mice indicated that induction of CYP1A1 was associated with increased numbers of Dlb-1 mutations. Mutation induction in Ahr-non-responsive mice in the absence of detectable CYP1A1 in either liver or small intestine indicates that an appreciable portion of B[a]P activation to a genotoxin must be by other than a CYP1A1 mediated route. These data show that B[a]P is a potent small intestinal mutagen at the Dlb-1 locus.

Animals↗
PubMed1999

Polymorphic debrisoquine 4-hydroxylase activity in the rat is due to differences in CYP2D2 expression.

The female Dark Agouti rat is widely used as an animal model for the CYP2D6 poor metabolizer phenotype, males of other strains such as Sprague Dawley or Wistar serving as models for the extensive metabolizer phenotype. To determine the relative level of expression of CYP2D enzymes in the liver of female and male Dark Agouti, Sprague Dawley and Wistar rats, anti-peptide antibodies were raised in rabbits against short synthetic peptides representing the C-termini of the rat P450 enzymes CYP2D1, CYP2D2, CYP2D3, CYP2D4 and CYP2D5. In immunoblotting studies, it was found that the hepatic expression of CYP2D1 was greater in Dark Agouti rats than Sprague Dawley or Wistar rats. In contrast, hepatic CYP2D2 was 30-40-fold less abundant in female Dark Agouti than female Sprague Dawley or Wistar rats and six- to eightfold less abundant in male Dark Agouti than male Sprague Dawley or Wistar rats. No hepatic CYP2D3 could be detected in either sex of any of the three strains. Hepatic CYP2D4 expression was generally greater in male than female rats, and higher in Dark Agouti compared with Sprague Dawley or Wistar strains. CYP2D5 was expressed in the livers of female and male Dark Agouti rats but not in female Sprague Dawley or Wistar rats. This form was variably expressed in livers of male Sprague Dawley and Wistar rats. Hepatic debrisoquine 4-hydroxylase activity was markedly reduced in female and male Dark Agouti rats as compared to Sprague Dawley or Wistar rats and correlated (r = 0.88; P < 0.001) with the hepatic CYP2D2 content. Recombinant CYP2D2 was 18-fold more active at catalysing the 4-hydroxylation of debrisoquine than CYP2D1. Furthermore, quinine markedly inhibited CYP2D2-mediated debrisoquine and metoprolol oxidation, while quinidine, its diastereoisomer, inhibited the reactions to a lesser extent. In conclusion, these results show that impaired debrisoquine 4-hydroxylase activity in the female Dark Agouti rat is due to low levels of CYP2D2.

Animals↗
PubMed1999

Effect of calcium channel antagonists nifedipine and nicardipine on rat cytochrome P-450 2B and 3A forms.

Calcium channel antagonists are widely prescribed for treatment of hypertension. In this study, we examined whether treatment with the calcium channel antagonists, nicardipine, nifedipine or diltiazem, alters cytochrome P-450 2B or 3A (CYP2B or CYP3A, respectively) expression in rat liver. Western blot analyses were undertaken using antibodies specific for one or several members of these cytochrome P-450 subfamilies. Nicardipine was found to be an effective inducer of CYP3A; in particular, CYP3A23 was increased approximately 36-fold following treatment with 100 mg of nicardipine/kg/day. Nicardipine induced CYP2B forms up to approximately 3.1-fold. Nifedipine did not alter CYP3A expression but did increase CYP2B expression such that total CYP2B, CYP2B1, and CYP2B2v (a splice variant of CYP2B2) were increased approximately 5- to 15-fold after treatment with 100 mg of nifedipine/kg/day, with increases in benzyloxyresorufin O-dealkylase and erythromycin N-demethylase activities, respectively. The distinct differences in cytochrome P-450 induction profile induced by nicardipine and nifedipine suggest that they may enhance cytochrome P-450 expression by different mechanisms unrelated to their effects on calcium channels.

Animals↗
PubMed1998

Development of a comprehensive panel of antibodies against the major xenobiotic metabolising forms of cytochrome P450 in humans.

Mono-specific antibodies against the human cytochrome P450 (P450) enzymes CYP1A1, CYP1A2, CYP1B1, CYP2A6, CYP2B6, CYP2D6, CYP2E1, CYP3A4, CYP3A5 and CYP4A11 and an antibody that binds to CYP2C8, CYP2C9 and CYP2C19 have been produced by immunising rabbits with synthetic peptides representing small regions of each of these P450 enzymes. The specificity of the antibodies was confirmed by immunoblotting using recombinant P450 enzymes and samples of human hepatic microsomal fraction. Each of the antibodies bound only to their respective target P450 enzyme(s). The relative intensity of immunoreactive bands was compared with a variety of P450 activities and correlations were found between CYP1A2 and phenacetin O-deethylase activity, CYP2A6 and coumarin 7-hydroxylase activity, CYP2C9 and tolbutamide 4-hydroxylase activity, CYP2C19 and S-mephenytoin 4-hydroxylase activity, CYP2D6 and debrisoquine 4-hydroxylase activity, CYP2E1 and chlorzoxazone 6-hydroxylase activity, CYP3A4 and midazolam 1'-hydroxylase activity, and CYP4A11 and lauric acid 12-hydroxylase activity. A proportion of the 30 liver samples examined lacked CYP2A6 (7%), CYP2C19 (10%) or CYP2D6 (13%), consistent with the polymorphic expression of these P450 enzymes in human liver. Although CYP3A5 was detected in most individuals (97%), expression was polymorphic with 20% containing substantially higher levels. CYP2B6 was expressed in 20% of the human liver samples, with one sample containing a particularly high level. No immunodetectable CYP1A1 or CYP1B1 was found, consistent with the low level of expression of these P450 enzymes in human liver. The results demonstrate the utility of the antipeptide approach for producing specific antibodies against human P450 enzymes, enabling a comprehensive panel of antibodies against human P450 enzymes to be produced.

Amino Acid Sequence↗
PubMed1998

Reduced hepatic expression of CYP7A1 and CYP2C13 in rats with spontaneous hyperlipidaemia.

A strain of hyperlipidaemic Sprague-Dawley (HSD) rat was compared with normal Sprague-Dawley (SD) rats for expression of cholesterol 7alpha-hydroxylase activity (CYP7A1) and other cytochrome P450 (P450) enzymes in liver. Hepatic microsomal CYP7A1 activity in male HSD rats was 2-3-fold lower than in male SD rats with CYP7A1 apoprotein levels being similarly reduced. CYP7A1 expression was subject to diurnal variation in HSD rats as found in SD rats. Treatment of HSD rats with cholestyramine caused an increase in hepatic microsomal cholesterol 7alpha-hydroxylase activity of 3.3-fold compared with a 3.5-fold increase in SD rats with similar changes in apoprotein levels. These results indicate that the lower activity in HSD rats is not due to a defect in the catalytic activity of the enzyme, regulation affecting diurnal variation or regulation through bile acid feedback inhibition. No difference between hepatic microsomal methoxyresorufin-O-demethylase, benzoxyresorufin-O-debenzylase or chlorzoxazone 6-hydroxylase activities in SD and HSD rats was found, nor was there any difference in the levels of CYP1A2, CYP2D1, CYP2E1, CYP3A1, CYP3A2 or NADPH cytochrome P450 reductase determined by immunoblotting using specific anti-peptide antibodies. However, unlike in male SD rats, CYP2C13 was absent in male HSD rats and this was associated with a two-fold reduction in testosterone 6beta-hydroxylase activity. In conclusion, while HSD rats do not have a general reduction in P450 levels, they do lack CYP2C13 and have lowered cholesterol 7alpha-hydroxylase activity, as a result of a reduced level of expression of the enzyme.

Animals↗
PubMed1998

Identification of CYP2E1 in marmoset monkey.

CYP2E1 is the main enzyme responsible for chlorzoxazone 6-hydroxylase activity in human liver. Here, it is shown that marmoset monkey liver microsomal fraction catalyses this reaction at a similar rate and with a similar Km to human liver and that the activity is increased 4-fold in marmosets treated with isoniazid, a known inducer of CYP2E1. This indicates that CYP2E1 is present in marmoset liver. However conversely, an anti-peptide antibody targeted against the C-terminus of human and cynomolgus monkey CYP2E1 (Val-Ile-Pro-Arg-Ser) failed to bind to marmoset monkey hepatic microsomal fraction. To investigate if there is a difference in the C-terminus of CYP2E1 in these species, this region of marmoset CYP2E1 was sequenced following amplification of marmoset liver cDNA with primers selected according to conserved regions identified in human and cynomolgus monkey CYP2E1. It was found that the deduced amino acid sequence of marmoset CYP2E1 in this region is very similar to human CYP2E1, but due to two base differences in the marmoset nucleic acid sequence, the C-terminus of marmoset CYP2E1 is extended by 2 amino acids, i.e. Val-Ile-Pro-Arg-Ser-Ser-Val. This difference is sufficient to prevent the binding of an antibody raised against the C-terminus of human CYP2E1. The expression of CYP2E1 in the marmoset was confirmed by raising an antibody against the deduced C-terminus of marmoset CYP2E1 (Pro-Arg-Ser-Ser-Val). In immunoblotting, this antibody bound to a single protein of 54 kDa in marmoset liver microsomal fraction. The intensity of the band was increased in isoniazid-treated marmosets, consistent with induction of CYP2E1. The antibody did not recognise human or cynomolgus monkey CYP2E1. This was expected since the immunising peptide sequence does not occur in these enzymes. The results demonstrate the presence of CYP2E1 in marmoset liver and illustrate the importance of the C-terminus for the production of specific antibodies against P450 enzymes.

Amino Acid Sequence↗
PubMed1998

S-phase-specific activation of Cds1 kinase defines a subpathway of the checkpoint response in Schizosaccharomyces pombe.

Checkpoints that respond to DNA structure changes were originally defined by the inability of yeast mutants to prevent mitosis following DNA damage or S-phase arrest. Genetic analysis has subsequently identified subpathways of the DNA structure checkpoints, including the reversible arrest of DNA synthesis. Here, we show that the Cds1 kinase is required to slow S phase in the presence of DNA-damaging agents. Cds1 is phosphorylated and activated by S-phase arrest and activated by DNA damage during S phase, but not during G1 or G2. Activation of Cds1 during S phase is dependent on all six checkpoint Rad proteins, and Cds1 interacts both genetically and physically with Rad26. Unlike its Saccharomyces cerevisiae counterpart Rad53, Cds1 is not required for the mitotic arrest checkpoints and, thus, defines an S-phase specific subpathway of the checkpoint response. We propose a model for the DNA structure checkpoints that offers a new perspective on the function of the DNA structure checkpoint proteins. This model suggests that an intrinsic mechanism linking S phase and mitosis may function independently of the known checkpoint proteins.

Cell Cycle Proteins↗
PubMed1998

X-ray diffraction indicates that active cross-bridges bind to actin target zones in insect flight muscle.

We report the first time-resolved study of the two-dimensional x-ray diffraction pattern during active contraction in insect flight muscle (IFM). Activation of demembranated Lethocerus IFM was triggered by 1.5-2.5% step stretches (risetime 10 ms; held for 1.5 s) giving delayed active tension that peaked at 100-200 ms. Bundles of 8-12 fibers were stretch-activated on SRS synchrotron x-ray beamline 16.1, and time-resolved changes in diffraction were monitored with a SRS 2-D multiwire detector. As active tension rose, the 14.5- and 7.2-nm meridionals fell, the first row line dropped at the 38.7 nm layer line while gaining a new peak at 19.3 nm, and three outer peaks on the 38.7-nm layer line rose. The first row line changes suggest restricted binding of active myosin heads to the helically preferred region in each actin target zone, where, in rigor, two-headed lead bridges bind, midway between troponin bulges that repeat every 38.7 nm. Halving this troponin repeat by binding of single active heads explains the intensity rise at 19.3 nm being coupled to a loss at 38.7 nm. The meridional changes signal movement of at least 30% of all myosin heads away from their axially ordered positions on the myosin helix. The 38.7- and 19.3-nm layer line changes signal stereoselective attachment of 7-23% of the myosin heads to the actin helix, although with too little ordering at 6-nm resolution to affect the 5.9-nm actin layer line. We conclude that stretch-activated tension of IFM is produced by cross-bridges that bind to rigor's lead-bridge target zones, comprising < or = 1/3 of the 75-80% that attach in rigor.

Actins↗
PubMed1998

Co-localization of P450 enzymes in the rat substantia nigra with tyrosine hydroxylase.

Susceptibility to develop Parkinson's disease has been linked to abnormalities of P450 enzyme function. Multiple P450 enzymes are expressed in brain but the relationship of these to Parkinson's disease is unknown. We have investigated the expression of P450 enzymes in the rat substantia nigra and their co-localization in tyrosine hydroxylase-positive neurons and astrocytes. Immunohistochemistry was performed using anti-peptide antisera against the following P450 enzymes: CYP1A1, CYP1A2, CYP2B1/2, CYP2C12, CYP2C13/2C6, CYP2D1, CYP2D4, CYP2E1, CYP3A1, CYP3A2 and NADPH-P450 oxidoreductase. Immunoreactivity in nigral cells was found only for CYP2E1 and CYP2C13/2C6. CYP2E1 immunoreactivity was localized to many midbrain nuclei including the substantia nigra pars compacta but not the substantia nigra pars reticulata while immunoreactivity to CYP2C13/2C6 was found in the substantia nigra pars compacta, substantia nigra pars reticulata and many other midbrain nuclei. Sections of rat midbrain double labelled for either CYP2E1 or CYP2C13/2C6 and tyrosine hydroxylase or glial fibrillary acidic protein were examined for co-localization by confocal laser scanning microscopy. CYP2E1 and CYP2C13/2C6 immunoreactivity was found in tyrosine hydroxylase-positive neurons in the substantia nigra pars compacta but not in glial cells. CYP2C13/2C6, but not CYP2E1, was also found in non-glial, non-tyrosine hydroxylase-expressing cells in the substantia nigra pars reticulata. Isoniazid induction increased CYP2E1 fluorescence signal intensity from nigral dopaminergic neurons. At least two P450 enzymes are found in nigral dopamine containing cells and one, namely CYP2E1, is selectively localized to this cell population. CYP2E1 is a potent generator of free radicals which may contribute to nigral pathology in Parkinson's disease. The expression of CYP2E1 in dopaminergic neurons in substantia nigra raises the possibility of a causal association with Parkinson's disease.

Animals↗
PubMed1998

Myocardial preconditioning: mechanisms and man.

Myocardial preconditioning describes the profound myocardial protection that follows a short episode of sublethal ischaemia. Adenosine is produced in ischaemic myocardium and is thought to be an important trigger of the protective mechanism. The exact pathway awaits full elucidation but activation of G proteins and subsequently protein kinase C appear to be important signals. End effectors responsible for delaying cell death include opening of K+ATP ion channels and the transcription of a family of cytoprotective proteins. Absolute proof that preconditioning occurs in man is still awaited, although cross clamping of the aorta during cardiac surgery, balloon inflation during coronary angioplasty, warm-up angina and preinfarction angina are surrogate models supporting its existence. A clearer understanding of the protective mechanisms involved could lead to the development of novel therapeutic agents that could save the infarcting myocardium.

Animals↗
PubMed1997

Developmental changes in the constitutive and inducible expression of cytochrome P450 3A2.

Using a CYP3A2-specific oligonucleotide and an antipeptide antibody raised against the C terminus of CYP3A2 (VINGA) it is demonstrated that metyrapone administration to adult (12 weeks old) but not immature (3 weeks old) male Sprague Dawley rats induces the hepatic expression of CYP3A2 mRNA and protein. The constitutively expressed level of CYP3A2 protein in adult male rats is markedly lower than the levels expressed in immature rats as determined using the anti-VINGA antibody, in contrast to previous reports using antibodies that do not discriminate between CYP3A forms. Hepatic microsomal CYP3A2 protein expression, examined between 3 and 15 weeks of age, is extinguished between 9 and 12 weeks of age in contrast to immunoreactive CYP3A protein (determined using a nonselective antibody) and CYP3A-dependent androstenedione 6beta-hydroxylase activity. These data suggest that the regulation of the induction of CYP3A2 is developmentally controlled and that the major expressed adult form(s) of constitutively expressed CYP3A is not CYP3A2.

Animals↗