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Vol. 280, Issue 3, 1463-1470, 1997
Department of Pathology, University of California in Irvine, Irvine, California
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Abstract |
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 Top
Abstract
Introduction
Materials & Methods
Results
Discussion
References
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Recently nitric oxide (NO) was suggested as a final mediator of
down-regulation of cytochrome P450 by bacterial lipopolysaccaride (LPS). One proposed mechanism is based on the ability of NO to effectively bind to cytochrome P450 heme iron. However, other evidences
exist demonstrating down-regulation of P450 proteins by LPS as well as
by different cytokines. Therefore, it is the purpose of our study to
investigate the relationship between NO and different P450 proteins in
rat liver. One group of Sprague-Dowley rats was treated with LPS for 24 hr and another group was given NO synthase inhibitors,
NG-nitro L-arginine methyl ester or
aminoguanidine at 0, 3, 6, 10 and 20 hr after LPS. LPS treatment caused
a 20-fold increase in plasma nitrates, which was almost completely
abolished by NO synthase inhibitors. LPS caused a substantial
inhibition of the activities of 16
- and 6
-androstenedione
hydroxylation, 7-ethoxyresorufin- and
7-pentoxyresorufin-O-dealkylation (EROD, PROD) that was
fully prevented by cotreatment with NG-nitro
L-arginine methyl ester and aminoguanidine. Western
blotting showed that the apoproteins of 3A2, 2C11, 1A2 and 2B1/2 were
suppressed and NOS inhibitors showed from 29% (3A2) to 100% (2C11)
protection of corresponding apoprotein from suppression by LPS. The
changes in apoprotein were largely due to changes in corresponding mRNA levels, as demonstrated by Northern blotting. Thus, NO appears to be
one of the mediators of the inhibition of 2C11, 3A2, 1A2 and 2B1/2
isozymes by LPS in rat liver.
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Introduction |
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Top
Abstract
Introduction
Materials & Methods
Results
Discussion
References
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CYP microsomal monooxygenases
compose a large but closely related superfamily of distinct gene
products with diverse substrate specificities. An intact male rat liver
contains a number of P450 isoforms, the major ones (CYP2C11 and CYP3A2)
being constitutive and sex-specific. Exposure of other isoforms to a
variety of chemicals, i.e., phenobarbital and
3-methylcholanthrene, can preferentially induce them (for review, see
Porter and Coon, 1991
; Soucek and Gut, 1992). Many studies have
documented a reduction in cytochrome P450-mediated metabolism in the
liver, lungs and other organs of rats exposed to LPS or other cytokines
(Sonawane and Yaffe, 1982; Morgan, 1989; Sakai et al.,
1992).
The discovery of NO as a biological mediator has revealed a plethora of
functions attributed to this molecule. NO is produced in large
quantities by certain cells of the immune system during host-defense
response and can target different pathogenic organisms and tumor cells.
Many effects of NO result from modulation of enzyme activity through
the binding of NO to prosthetic iron complexes (Henry et
al., 1991). Recently, NO-induced intracellular heme loss and
increased heme degradation in hepatocytes has been demonstrated (Kim
et al., 1995a). However, decreased P450 activities
accompanying intracellular heme loss were restored by the addition of
heme in isolated microsomes suggesting the mechanism for the loss of P450 activities resides solely in the alterations of heme metabolism. Using EPR, Chamulitrat et al. (1995) were able to identify
cytochromes P450 and P420 as intracellular targets of NO in the livers
of mice treated with Coryne-bacterium parvum and LPS. We and
others earlier implicated NO as a mediator of the known decrease in
cytochrome P450-dependent metabolism caused by LPS and suggested that
the binding of NO to the prosthetic heme of P450 might result in an inhibition of CYP1A1/2- and CYP2B1/2-mediated activities. These changes
were reported both when NO was added exogeneously (Khatsenko et
al., 1992; Wink et al., 1993) and when produced
endogenously in vitro (Stadler et al., 1994;
Osawa et al., 1995) or in vivo (Khatsenko
et al., 1993; Oyekan, 1995; Kim et al., 1995b).
These studies support the notion that the inhibition of P450 activities resides in the altered state of prosthetic heme. However, there are
many reports demonstrating that an administration of LPS or other
cytokines results in decreased P450 apoproteins (Morgan, 1991; Sakai
et al., 1992; Stadler et al., 1994). Further, NO
appears to be responsible for down-regulation of certain apoproteins of P450 isozymes in cultured hepatocytes. However, to the best of our
knowledge the effect of NO on CYP apoproteins has not been studied
in vivo. This is important because using a pure hepatocyte culture model imposes an inherent limitation. Earlier studies have
shown the importance of Kupffer cell and hepatocyte interactions on the
treatment with LPS, IFN-
or with dextran sulfate (reviewed by
Renton, 1983). Hence in vivo study should be able to
elucidate the role played by NO derived from hepatocytes, Kupffer cells and endothelial cells.
We report that in rats NO appears to play a similar role as demonstrated for hepatocyte culture in down-regulation of several P450 isozymes and that there appears to be a differential suppression of CYP2C11, CYP3A2 and CYP2B, the degree of which are different from that seen in hepatocyte culture.
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Materials and Methods |
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Top
Abstract
Introduction
Materials & Methods
Results
Discussion
References
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Preparation of hepatic microsomes. Male Sprague-Dowley, CD strain, viral antigen- and pathogen-free rats (250-270 g) were obtained from Charles River (Wilmington, MA). They were allowed food (rodent laboratory chow) and water ad libitumn and were kept on a 12-hour, light-dark cycle in the University of California, Irvine animal facility. One group of animals was treated with a single injection of Escherichia coli LPS (1.2 mg/kg, i.p.) for 24 hr. Another group received either L-NAME (150 mg/kg, i.p.) or AG (100 mg/kg, i.p.) alone or in combination with LPS at 0, 3, 6, 10 and 20 hr after endotoxin. The control group received endotoxin-free saline only.
At the end of the experiment, the rats were anesthetized by an i.p. injection of 70 mg/kg of pentobarbital sodium and the livers were removed and kept at -80°C. All subsequent steps were carried out at 4°C and microsomes were prepared as described earlier (Khatsenko et al., 1993). The washed microsomal pellets were
resuspended in 25 mM Tris, pH 7.25, 1.15% KCl, 20% glycerol and
stored at -80°C. For RNA preparation, removed tissues were
immediately frozen by submersion in liquid nitrogen and stored at
-80°C until use.
Measurement of cytochromes P450 and b5 and total microsomal
heme.
Spectra were recorded using a Shimadzu UV-250 double-beam
spectrophotometer. Cytochrome b5 and CO-bound cytochrome
P450 contents were determined by the method of Omura and Sato (1964).
Total microsomal heme was measured by the pyridine hemochrome method (Berry and Trumpower, 1987). A total of 500 µl of pyridine solution (50%, v/v) with 0.2 N NaOH was mixed with an equal volume of microsome solution (1 mg/ml), followed by addition of a few grains of sodium dithionite. Spectra were recorded in reference to a blank containing buffer and pyridine solution. The heme concentration was calculated from a standard curve of hemoglobin.
Cytochrome P450 activity.
CYP1A1/2 specific activity was
determined by 7-EROD and CYP2B1/2 specific activity by 7-PROD by the
method of Burke and Mayer (1983). CYP2C11 and CYP3A2 activities were
assessed through the reactions of 16- and 6-AD hydroxylation,
using corticosterone as an internal standard for recovery, as described
earlier (Waxman and Walsh, 1983; Khatsenko et al., 1991).
Plasma [NOx] assay. NO production was evaluated by measuring total [NOx] in plasma. A total of 20 µl of sample standard was mixed with 50 µl of 100 mM Tris buffer, pH 7.5, 10 µl of nitrate reductase (10 units/ml in 100 mM Tris, pH 7.6), 5 µl of 1 mM FAD and 5 µl of 10 mM NADPH in the 96-well plate. Reaction was allowed to proceed for 1 hr at 37°C in the dark. Next, 10 µl of the mixture (500 µl of 200 mM sodium pyruvate and 30 µl of lactate dehydrogenase) were added and incubate for 30 min at 37°C. Nitrates that converted to nitrites were detected by addition of 100 µl of Griess reagent (1% sulfonilic acid in 5% o-phosphoric acid, mixed with 0.1% N-1-naphtylene-diamine-H-chloride (1:1 v/v) at 550 nm.
Western blotting.
Ten percent polyacrylamide SDS-gel
electrophoresis was performed according to Laemmli (1970). Microsomal
proteins (5-10 µg/well) were transferred to nitrocellulose membrane
and probed with antibodies against P450 isoforms, according to supplied
protocol. To control the amount of protein loaded, either the membranes
were reversibly stained with Ponceau red or separate SDS-gels were run
for Coomassie blue staining. Peroxidase activity resulting from
specifically bound, horseradish peroxidase-conjugated, second
antibodies on the immunoblots was localized using Amersham, a
chemiluminescent reagent (Amersham Corp., Arlington Heights, IL). The
bands were analyzed with a LKB 2400 Gel Scan XL Laser densitometer.
Oligonucleotide probes.
For Northern blot analysis, specific
oligomer probes of the following sequences were used: 1) CYP2C11,
5
-TCTTCCAGAAAATTCCTCTCC-3 and 5-CCTCAGAGTGGTACTTGTTG T-3 (Yoshioka
et al., 1987) and 2) CYP3A2, 5-TATCTGGAATTCATTCATGAAGTA-3
(Ribeiro and Lechner, 1992) and 5-TCTATGGGTTCCAAGTCGGT-3 (Miyata
et al., 1994).
-CACCTCTAGCGGCGCAATAC-3 (Omiecinski et al., 1990).
All probes were labeled at the 5 end using 32P-ATP
(specific activity, 6000 Ci/mmol; Amersham) and T4-polynucleotide
kinase (Promega Co., Madison, WI).
Total RNA preparation and Northern blot. Total RNA was isolated from the frozen tissues by using UltraSpec II (BioTecx Laboratories, Inc., Houston, TX) according to supplied protocol. After washing with 75% ethanol and centrifugation, RNA was dissolved in FORMAzol (MRC, Inc., Cincinnati, OH) and stored at -80°C.
For Northern blot analysis, 20 µg of total RNA were denatured (65°C for 10 min), cooled, and electrophoresed on 1.5% agarose gel containing 5% formaldehyde. The denatured RNA was then transferred to a Nylon+ membrane (Boehringer Mannheim, Indianapolis, IN) in 10 × SSC, left overnight and then UV-cross-linked on a UV Stratalinker 2400 (Stratagene, Menasha, WI). The membranes were prehybridized for 2 hr in QuickHyb solution (Stratagene) and hybridized overnight in a solution containing 32P-labeled DNA oligomer along with 100 µg/ml of denatured salmon sperm DNA at 57°C. Filters were washed twice in 2 × SSPE and once in 2 × SSPE 0.1% SDS for 30 min at 37°C. Autoradiography was performed by exposing the filters overnight to Kodak X-Omat XAR film at -80°C. The filters were then washed with 0.1 × SSC, 0.5% SDS for 15 min at 95°C and rehybridized with the 18s RNA probe as described above. Relative mRNA levels were assessed by densitometry and normalized to 18s RNA.Protein assay.
Protein concentration was measured by the
dye-binding assay of Bradford (1976) with bovine serum albumin as
standard.
Materials. 7-Ethoxyresorufin and resorufin were purchased from Pierce (Rockford, IL) and 7-pentoxy-resorufin from Sigma Chemical Co. (St. Louis, MO). The monoclonal anti-rat CYP2C11 antibodies were purchased from Oxford Biomedical Research Inc. (Oxford, MI), although the polyclonal anti-CYP3A, anti-CYP2B1/2 were purchased from Amersham (Arlington Heights, IL). Finally, the oligonucleotide probes were custom-synthesized by Keystones (Menlo Park, CA). Other reagents were also purchased from Sigma.
Statistical analysis. The statistical significance of the difference between the control and experimental groups was determined by one-way analysis of variance.
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Results |
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Top
Abstract
Introduction
Materials & Methods
Results
Discussion
References
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Plasma [NOx], P450 and
b5.
Treatment of animals with LPS causes the
induction of NO synthesis (Hewett and Roth, 1993). In our experiment,
1.2 mg/kg LPS elicited after 24 hr 20- to 25-fold elevation in plasma
[NOx] levels in the treated animals (fig.
1). This elevation was largely prevented in animals
treated concurrently with NOS inhibitors L-NAME (91%) or AG (88%).
LPS treatment is known to result in a decline in microsomal heme
concentration as well as in cytochromes P450 and b5
concentrations (Bissel and Hammaker, 1976; Renton and Mannering, 1976).
Our experiments also caused a significant suppression of both
cytochrome P450 and cytochrome b5 concentrations (57 and
34%; see table 1). In agreement with our previous
report (Khatsenko et al., 1993) and with that of Kim
et al. (1995b), this loss of P450 and b5 heme
caused by LPS administration was substantially attenuated when LPS was
administered simultaneously with NOS inhibitors L-NAME (up to 61 and
96% of control) and AG (up to 65 and 100% of control, table 1).
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Monooxygenase activities.
Figure 2a illustrates
changes in the activity of the major cytochrome in male rat liver,
CYP2C11, after LPS treatment, both with and without L-NAME. CYP2C11
oxidases AD stereospecifically and regioselectively in the
16-position (Waxman and Walsh, 1983). The rate of 16-AD
hydroxylation decreased by 62% in the microsomes of rats after LPS
treatment. The activity of 16-AD hydroxylation was completely
protected from LPS suppression by cotreatment with L-NAME (100% of
control, fig. 2a).
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-AD hydroxylation), was inhibited 70% by LPS. This inhibition was
reduced to 20% by cotreatment with NOS inhibitor L-NAME (fig. 3a).
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Heme content and Western blot study. Suppression of CYP enzymatic activity is due either to functional inhibition or to a decrease in the apoprotein and/or heme moiety of CYP. To determine the roles played by these mechanisms, we measured the total microsomal heme concentration and carried out Northern and Western blot analysis.
Table 1 shows that the total extractable microsomal heme concentration decreased by 44% in the liver of rats after LPS treatment. Administration of either L-NAME or AG significantly modified the decrease of total microsomal heme content in the liver. Figure 2b shows the results of Western blotting of CYP2C11 and corresponding densitometric measurements, depicted in Figure 2a. CYP2C11 protein concentration decreased 52% after LPS treatment and the decrease was only 12% in LPS+L-NAME groups. Figure 3b shows the changes of the CYP3A protein concentration, demonstrating an 81% decrease after LPS administration compared to control levels. The decrease in CYP3A protein concentration was 52% in the LPS+L-NAME group, a value similar to that of the rats who received L-NAME alone. Figure 4b shows the results obtained for CYP2B protein concentration in the liver. CYP2B protein concentration fell to 25% of the control level after LPS treatment. The reduction was 56% of control values in the LPS+L-NAME group.Northern blot study. Figure 2, c and d illustrate results of the Northern blot of CYP2C11 mRNA and 18s RNA controls, respectively. Densitometric measurements that are corrected with the values from 18s rRNA are depicted in figure 2a. After LPS administration CYP2C11 mRNA was suppressed by 45%; this suppression was largely prevented in LPS+L-NAME group.
The results of the Northern blot of CYP3A2 and 18sRNA are shown in Figure 3, c and d. Densitometric measurements that are corrected with the values from 18s rRNA are shown in figure 3a. After LPS administration, CYP3A2 mRNA was reduced to 40% of the control levels and the reduction for the LPS+L-NAME group was 58% of control levels.| |
Discussion |
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Top
Abstract
Introduction
Materials & Methods
Results
Discussion
References
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Treatment of rats with endotoxin causes a release of many
cytokines and results in a substantial induction of NO synthase in the
liver, lungs and other organs. Because a high dose of LPS can lead to
death, in this experiment we used a dosage (1.2 mg/kg) that has been
shown not to produce endotoxic shock but to induce a cascade of
cytokines, known individually to suppress CYP activities (Morgan, 1989;
Wright and Morgan, 1990). NO induction by LPS was considered to be
the cause of an increase in the level of plasma and urinary
[NOx], a breakdown product of NO (Wagner et
al., 1983). We found that plasma [NOx] were greatly
increased 24 hours after LPS treatment (fig. 1), returning to basal
levels at 48 hr (data not shown). Current data are, therefore,
consistent with a dynamic [NOx], as measured by Tracey
et al. (1995) in Sprague-Dowley rats after LPS
administration.
Given that NO is difficult to detect in biological systems, NOS
inhibitors are valuable in evaluating the presence of NO in a cell or
tissue. The most promising approach to selectively inhibiting NOS
isozymes to date has been with arginine-based inhibitors. Among those
extensively used, L-NAME has been particularly useful, because it
penetrates the cell membrane due to its lipophilic nature (Kerwin
et al., 1995). In the cell system L-NAME undergoes the
deesterification and becomes an equivalent of
nitro-L-arginine, a potent inhibitor of all NOS isoforms
with the preference to constitutive NOS (Furfine et al.,
1993). Another inhibitor, used in this study, AG has received much
attention due to early recognition of its selectivity toward inducible
NOS, its low toxicity and potential clinical usefulness (Corbett
et al., 1992). In our study there were more similarities
than differences in the action of L-NAME and AG. What these data mean
in terms of constitutive and inducible NOS remains to be explored
further.
It has been known for decades that NO binds to the heme moiety of P450
and was used as a spin label probe for cytochrome P450 (O'Keefe
et al., 1978). However, only recently we (Khatsenko et al., 1992, 1993) and others (Wink et al., 1993; Stadler
et al., 1994) reported that treatment of these enzymes with
exogenously applied NO inhibits their catalytic activity. Wink et
al. (1993), using an in vitro model, made an
interesting observation of two distinct phases of CYP inhibition by NO
which led them to the suggestion that NO may inhibit CYP activity by
two distinct mechanisms.
As for an in vivo situation, there are also at least two
possible mechanisms to explain the inhibitory action of NO on CYP activity. One mechanism is likely to be the binding of NO to the heme
group in the catalytic center of these enzymes as we (Khatsenko et al., 1993) provided a spectral evidence that NO binds to
both ferrous and ferric state of P450. Further support of this
hypothesis comes from the work of Kim et al. (1995a) who
found microsomal heme loss and consequent increase in heme oxygenase
activity in isolated hepatocytes when NO biosynthesis was induced.
Furthermore, Chamulitrat et al. (1995) found a suppression
of EPR signals attributable to ferric low-spin cytochrome P450/P420
peaks in the livers of mice treated with C. parvum and
C. parvum + LPS. This finding shows that cytochromes
P450/P420 heme is a target of NO, contributing to nitrosyl signals
detected in vivo .
Another mechanism comes from studies in which cytokines and LPS
administrations have been shown to be accompanied with down-regulation of both CYP mRNA and proteins. It has been demonstrated that CYP2C11 apoprotein is markedly suppressed in rats receiving LPS (Morgan, 1989;
Wright and Morgan, 1990) as well as polyIC (Sakai et al., 1992). This suppression was attributed to the reduction in CYP2C11 mRNA
level (up to 89%) (Morgan, 1989). Fifty percent suppression of mRNA
for CYP3A2 by interferon- (Graig et al., 1990), 80%
suppression of CYP2E1 mRNA by LPS (Morgan, 1993) and 60% suppression
of CYP1A2 mRNA by polyIC (Sakai et al., 1992) have also been
reported. Our data uncover mainly the transcriptional effects of NO in
CYP gene expression. They are consistent with the study by
Stadler et al. (1994) who found that suppression of the
-napthoflavone-inducible CYP1A1 and CYP1A2
gene expression in hepatocytes by cytokines is regulated by NO. The
regulation occurs at the pretranslational level because they found an
apparent protection by NOS inhibitors of CYP1A1/2 proteins and mRNA
from suppression by cytokine mixture. Thus, it appears reasonable to
suggest that down-regulation observed by immunostimulants is biphasic
and is based on two mechanisms. Based on their data with heme
reconstitution, Kim et al. (1995a) proposed that in contrast
to inducible P450, the exclusive effect of NO on constitutive CYP is
the loss of the heme prosthetic group, with no appreciable decrease in
CYP protein. Because the authors did not correlate their findings with
any particular P450 isoform content and corresponding metabolism, it is
difficult to accept their hypothesis in lieu of our current findings.
Kim et al. (1995) claimed that the increase in heme
oxygenase and the decrease in 
-aminolevulinate synthetase activities in rats receiving LPS were due to NO-induced heme liberation. It is
noteworthy, that binding of IRF to iron responsive element, which is a
major mechanism in regulation of intracellular iron homeostasis, was
shown recently to be mediated by NO (Drapier et al., 1993;
Weiss et al., 1993). It, therefore, seems more likely to us
that intracellular heme may act as a second mediator of NO-dependent
suppression of P450 apoprotein expression. The recent finding that NO
regulates the expression of iron homeostasis proteins at the
pretranslational level in vitro gives a credit to the
speculation that NO could down-regulate cytochrome P450 apoprotein
expression indirectly via regulation of intracellular heme. Despite the
evidence that heme can down-regulate P450 levels in rat liver
(Srivastava et al., 1990), other reports contradict this
view (Padmanaban et al., 1989; Sinclair et al.,
1990). Further investigation of the role of heme in regulating of
cytochrome P450 apoprotein expression and role of NO in regulation of
microsomal heme in vivo is required to prove this
hypothesis.
Finally, in addition to specific biochemical effects of NO, it seems conceivable that its physiological action as vasodilator may contribute to the modulation of the expression of certain hepatic enymes, including P450. Decreased blood flow by NO can cause portal hypotension and therefore diminished liver oxygenation that result in protein synthesis inhibition (Srark and Szurszewski, 1992).
Wink et al. (1993) reported that various CYP-dependent
monooxygenase activities show differences in the susceptibility toward the inhibitory effects of NO, the observation consistent with the data
reported in this communication. Osawa et al. (1995) also provided data suggesting that cytokine mixture inhibits CYP2C11- and
CYP3A2-specific testosterone hydroxylation in primary hepatocytes to a
different degree. They found that the NOS inhibitor NMMA attenuated up
to 52% inhibition of CYP2C11 and up to 18% CYP3A2-mediated metabolism
from suppression by cytokines. Although no direct comparison can be
made between their in vitro data and our animals data, one
similarity was noticed: down-regulation by NO of CYP2C11 in these
experiments was mediated to a greater degree than CYP3A2. The reason
for this difference is not clear and requires additional studies.
Recently Carlson and Billings (1996) reported a study on the role of NO
in the cytokine-mediated regulation of cytochrome P450 in rat
hepatocytes. They found that during the treatment with TNF-, IL-1
as well as a mixture of TNF-, IL-1 and interferon- increased
the level of NO production accompanied by the decreased protein levels
of CYP1A2, CYP2C11, CYP2B and CYP3A2 whereas IL-6 decreased each CYP
enzyme without induction of NO synthesis. Thus, these results indicate
that in case of IL-6 the down-regulation of cytochrome P450 is NO
independent.
Regarding CYP protein changes in the experiments of these authors, a cytokine mixture gave the most pronounced supression of all isozymes as compared to each cytokine alone. Our results using LPS revealed the suppression of CYP2C11 and CYP2B1/2 proteins similar to that demonstrated by Carlson and Billings (74 vs. 67% and 46 vs. 41%, respectively). However, there was a significant discrepancy in case of CYP3A2 protein (80 vs. 38%), which needs to be explored further.
Thus, we are the first to describe the role of NO in the suppression of constitutive hepatic cytochrome P450 isozymes by LPS in vivo. It also suggests that the major mechanism of this is their down-regulation at pretranslational level.
Finally, NO was demonstrated to be involved in regulation of a variety
of heme (tryptophan-2,3-dioxygenase, catalase, cyclooxygenase and
cytochrome c) and nonheme (lipoxygenase, ribonucleotide reductase and
ferritin) iron and iron-sulfur proteins (NADPH:ubiquinone oxidoreductase, NADPH:succinate oxidoreductase,
Cis-aconitase; for review, see Henry et al.,
1991). Most of these enzymes are down-regulated by NO; however,
up-regulation of cGMP (Gruetter et al., 1980) and
cyclooxygenase has also been shown (Salvemini et al., 1993).
Our report on regulation of constitutive cytochrome P450 in
vivo by NO suggests the possible role of this molecule as a
universal regulator of iron-containing proteins.
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Acknowledgments |
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The authors thank Anna Khatsenko for the technical assistance.
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Footnotes |
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Accepted for publication November 5, 1996.
Received for publication August 8, 1996.
1 This work was supported by Grant HL-50450 from the National Heart Lung and Blood Institute of the National Institutes of Health, US Public Health Service.
Send reprint requests to: Dr. Yutaka Kikkawa, Professor and Chair, Department of Pathology, College of Medicine, University of California in Irvine, Irvine CA 92697-4800.
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Abbreviations |
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CYP, cytochrome P450; LPS, Escherichia coli lipopolysaccaride; L-NAME, NG-L-arginine methyl ester; AG, aminoguanidine; 7-EROD, 7-ethoxyresorufin O-deethylation; 7-PROD, 7-pentoxyresorufin O-dealkylation; NOS, nitric oxide synthase; IRF, iron regulatory factor; PB, phenobarbital; SDS, sodium dodecylsulfate; SSC, saline-sodium citrate; SSPE, saline-sodium phosphate-EDTA; MOPS, 3-[N-morpholino]propanesulphonic acid; AD, 4-androsten-3,17-dione.
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References |
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Top
Abstract
Introduction
Materials & Methods
Results
Discussion
References
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-aminolevulinic acid synthetase in the liver.
Arch. Biochem. Biophys.
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214: 9-15, 1980-hydroxylase (P450/6A) encoding CYP3A2: Comparison of the cDNA with P450 PCN2.
Arch. Biochem. Biophys.
314: 351-359, 1994[Medline].This article has been cited by other articles:
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 K.-i. Komine, T. Kuroishi, Y. Komine, K. Watanabe, J. Kobayashi, T. Yamaguchi, S.-i. Kamata, and K. Kumagai Induction of Nitric Oxide Production Mediated by Tumor Necrosis Factor Alpha on Staphylococcal Enterotoxin C-Stimulated Bovine Mammary Gland Cells Clin. Vaccine Immunol., January 1, 2004; 11(1): 203 - 210. [Abstract] [Full Text] [PDF]
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 H. Hara and T. Adachi Contribution of Hepatocyte Nuclear Factor-4 to Down-Regulation of CYP2D6 Gene Expression by Nitric Oxide Mol. Pharmacol., January 1, 2002; 61(1): 194 - 200. [Abstract] [Full Text] [PDF]
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L. Ferrari, N. Peng, J. R. Halpert, and E. T. Morgan Role of Nitric Oxide in Down-Regulation of CYP2B1 Protein, but Not RNA, in Primary Cultures of Rat Hepatocytes Mol. Pharmacol., July 1, 2001; 60(1): 209 - 216. [Abstract] [Full Text]
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A. Yaghi, C. D. Webb, J. A. Scott, S. Mehta, J. R. Bend, and D. G. McCormack Cytochrome P450 Metabolites of Arachidonic Acid but Not Cyclooxygenase-2 Metabolites Contribute to the Pulmonary Vascular Hyporeactivity in Rats with Acute Pseudomonas Pneumonia J. Pharmacol. Exp. Ther., April 12, 2001; 297(2): 479 - 488. [Abstract] [Full Text]
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T. Li-Masters and E. T. Morgan Effects of Bacterial Lipopolysaccharide on Phenobarbital-Induced CYP2B Expression in Mice Drug Metab. Dispos., March 1, 2001; 29(3): 252 - 257. [Abstract] [Full Text]
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 K. Kitaichi, L. Wang, K. Takagi, M. Iwase, E. Shibata, M. Nadai, K. Takagi, and T. Hasegawa Decreased Antipyrine Clearance following Endotoxin Administration: In Vivo Evidence of the Role of Nitric Oxide Antimicrob. Agents Chemother., November 1, 1999; 43(11): 2697 - 2701. [Abstract] [Full Text]
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C.-S. Park, H.-M. Baek, W.-G. Chung, K.-H. Lee, S.-D. Ryu, and Y.-N. Cha Suppression of Flavin-Containing Monooxygenase by Overproduced Nitric Oxide in Rat Liver Mol. Pharmacol., September 1, 1999; 56(3): 507 - 514. [Abstract] [Full Text]
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E. T. Morgan, M. B. Sewer, H. Iber, F. J. Gonzalez, Y.-H. Lee, R. H. Tukey, S. Okino, T. Vu, Y.-H. Chen, J. S. Sidhu, et al. Physiological and Pathophysiological Regulation of Cytochrome P450 Drug Metab. Dispos., December 1, 1998; 26(12): 1232 - 1240. [Abstract] [Full Text]
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M. B. Sewer and E. T. Morgan Down-Regulation of the Expression of Three Major Rat Liver Cytochrome P450S by Endotoxin In Vivo Occurs Independently of Nitric Oxide Production J. Pharmacol. Exp. Ther., October 1, 1998; 287(1): 352 - 358. [Abstract] [Full Text]
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 C. J. Hanke, J. G. Drewett, C. R. Myers, and W. B. Campbell Nitric Oxide Inhibits Aldosterone Synthesis by a Guanylyl Cyclase-Independent Effect Endocrinology, October 1, 1998; 139(10): 4053 - 4060. [Abstract] [Full Text] [PDF]
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M. B. Sewer, T. B. Barclay, and E. T. Morgan Down-Regulation of Cytochrome P450 mRNAs and Proteins in Mice Lacking a Functional NOS2 Gene Mol. Pharmacol., August 1, 1998; 54(2): 273 - 279. [Abstract] |
