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PubMed1978

Studies on human liver bilirubin-UDP-glycosyl transferase. I. Assay methods for bilirubin-UDP-glucuronyl and -xylosyl transferases of human liver specimen.

Micromethods for estimation of bilirubin uridine diphosphate-glucuronyl and -xylosyl transferases in liver are described. With these methods, a liver specimen as small as 10 mg is sufficient for assay of either enzyme activity and 15 mg is sufficient for assay of both enzymes. Normal values for livers with minimal elevation of SGOT and minimal histological change were 0.260-0.400 U/g protein for glucuronyl transferase and 0.142-0.302 U/g protein for xylosyl transferase.

Bilirubin↗
PubMed1994

Farnesyl-protein transferase and geranylgeranyl-protein transferase assays using phosphocellulose paper absorption.

Farnesyl-protein transferase catalyzes the reaction of farnesyl pyrophosphate and its acceptors to yield farnesyl protein and pyrophosphate. Geranylgeranyl-protein transferases are distinct enzymes that catalyze the reaction of geranylgeranyl pyrophosphate and their acceptors. We used tritiated isoprenoid pyrophosphate donors and synthetic peptide acceptors to measure enzyme activities. The peptide acceptors contained basic amino acid residues on the amino terminus of tetrapeptide substrate determinants specific for each enzyme. Following the incubation, portions of the reaction mixture were applied to numbered phosphocellulose paper strips that were immersed in 95% ethanol/75 mM phosphoric acid (1/1; v/v). Acid promoted binding of positively charged peptide substrates and products to the negatively charged paper, and alcohol eluted the radioactive prenyl groups. Paper strips were processed in the same container in batches for 40 min, and radioactivity adsorbed to the strips was then measured by liquid scintillation spectrometry. The use of peptides makes the expression and purification of recombinant substrates in bacteria unnecessary. However, most proteins bind quantitatively to phosphocellulose at acidic pH, and the washing procedure developed for peptide substrates is applicable for measuring prenyltransferase activities with recombinant Ras proteins as acceptor.

Absorption↗
PubMed1997

Characterization of Ha-ras, N-ras, Ki-Ras4A, and Ki-Ras4B as in vitro substrates for farnesyl protein transferase and geranylgeranyl protein transferase type I.

Ras proteins are small GTP-binding proteins which are critical for cell signaling and proliferation. Four Ras isoforms exist: Ha-Ras, N-Ras, Ki-Ras4A, and Ki-Ras4B. The carboxyl termini of all four isoforms are post-translationally modified by farnesyl protein transferase (FPT). Prenylation is required for oncogenic Ras to transform cells. Recently, it was reported that Ki-Ras4B is also an in vitro substrate for the related enzyme geranylgeranyl protein transferase-1 (GGPT-1) (James, G. L., Goldstein, J. L., and Brown, M. S. (1995) J. Biol. Chem. 270, 6221-6226). In the current studies, we compared the four isoforms of Ras as substrates for FPT and GGPT-1. The affinity of FPT for Ki-Ras4B (Km = 30 nM) is 10-20-fold higher than that for the other Ras isoforms. Consistent with this, when the different Ras isoforms are tested at equimolar concentrations, it requires 10-20-fold higher levels of CAAX-competitive compounds to inhibit Ki-Ras4B farnesylation. Additionally, we found that, as reported for Ki-Ras4B, N-Ras and Ki-Ras4A are also in vitro substrates for GGPT-1. Of the Ras isoforms, N-Ras is the highest affinity substrate for GGPT-1 and is similar in affinity to a standard GGPT-1 substrate terminating in leucine. However, the catalytic efficiencies of these geranylgeranylation reactions are between 15- and 140-fold lower than the corresponding farnesylation reactions, largely reflecting differences in affinity. Carboxyl-terminal peptides account for many of the properties of the Ras proteins. One interesting exception is that, unlike the full-length N-Ras protein, a carboxyl-terminal N-Ras peptide is not a GGPT-1 substrate, raising the possibility that upstream sequences in this protein may play a role in its recognition by GGPT-1. Studies with various carboxyl-terminal peptides from Ki-Ras4B suggest that both the carboxyl-terminal methionine and the upstream polylysine region are important determinants for geranylgeranylation. Furthermore, it was found that full-length Ki-Ras4B, but not other Ras isoforms, can be geranylgeranylated in vitro by FPT. These findings suggest that the different distribution of Ras isoforms and the ability of cells to alternatively process these proteins may explain in part the resistance of some cell lines to FPT inhibitors.

Alkyl and Aryl Transferases↗
PubMed2004

[Killing effect of adenovirus mediated fusion gene cytosine and deaminase uracil phosphoribosyl transferase directed by glutathione S-transferase P1 promoter on cisplatin-resistant ovarian cancer cells in vitro].

OBJECTIVE: To construct an adenoviral vector in which the fusion gene cytosine and uracil phosphoribosyl (UPP) transferase was directed by glutathione S-transferase P1 (GSTP1) promoter, and to investigate specific killing effect of the suicide gene system on cisplatin-resistant ovarian cancer cells. METHODS: Recombinant adenovirus was generated through homologous recombination in bacteria. A2780 and A2780/DDP cells were infected with Ad and then received flucytosine (5-FC) administration. The relative survival of these cells was tested. And a bystander effect was observed by mixing gene-transferred and gene-untransferred A2780/DDP cells with 5-FC. RESULTS: In vitro, when MOI was 100 and 5-FC was 250 micro g/ml, relative survival rate of A2780/DDP cells was only (3.6 +/- 1.0)%; that of A2780 cells was (76.5 +/- 2.8)%. Significant bystander effect was caused by CD-UPP gene and 20% gene-transferred A2780/DDP cells induced 80.3% of total cells to death. CONCLUSION: Recombinant adenovirus carrying CD-UPP gene driven by GSTP1 promoter has a specific killing effect on cisplatin-resistant ovarian cancer cells.

Adenoviruses, Human↗
PubMed1988

Biological effects in a chemical factory with mutagenic exposure. II. Analysis of unscheduled DNA synthesis and adenosine diphosphate ribosyl transferase, epoxide hydrolase, and glutathione transferase in resting mononuclear leukocytes.

A chemical plant, where an increased number of non-Hodgkin's lymphomas and myelomas had been observed, was monitored for genotoxic effects occurring in peripheral mononuclear leukocyte samples from 76 exposed workers. Biochemical markers sensitive to DNA repair and drug metabolism were used as the indicators of genotoxic risk. Unscheduled DNA synthesis (UDS) and covalent binding induced by N-acetoxy-N-acetyl-2-aminofluorene (NA-AAF) and constitutive and gamma ray induced adenosine diphosphate ribosyl transferase (ADPRT) activities were highly and significantly elevated over the corresponding values for a control group of 48 postal workers. Microsomal and soluble epoxide hydrolases and glutathione transferase activities directed towards trans-stilbene oxide and 1-chloro-2,4-dinitrobenzene were not significantly altered in the exposed group. The exposure in this factory was complex, involving over 100 chemicals including several well known carcinogens. However, no apparent significant associations to exposure could be established.

Acetoxyacetylaminofluorene↗
PubMed2002

Functional relationship of alpha-glutathione S-transferase and glutathione S-transferase activity in machine-preserved non-heart-beating donor kidneys.

alpha-Glutathione S-transferase (alpha-GST) is a biochemical parameter used to estimate the amount of proximal tubule damage to a kidney. In normal clinical practice, the concentration of alpha-GST in urine is determined by a rather time-consuming immunochemical test, the enzyme-linked immunosorbent assay (ELISA). Kidneys from non-heart-beating (NHB) donors are perfused prior to transplantation. The determination of alpha-GST concentration in the perfusate to monitor damage is also done by means of an ELISA test. However, because this is a time-consuming method, it would be helpful to find a parameter proportional to GST concentrations that would be available within minutes. We therefore compared the method of determining alpha-GST concentration via ELISA with that of determining the enzymatic activity of GST, which is much faster (results available within 10 min). The comparison was made using 150 preserved kidneys that had been perfused for 6 h. The correlation was found to be very good, as indicated by the linear regression data: r=0.954, P<0.001. pi-Glutathione S-transferase (pi-GST) was also determined by means of an ELISA test, and the concentration of pi-GST was compared with the enzymatic activity of the "total" GST. The precision of the enzymatic method, given by intra- and interassay variation, was 1.5% and 10.5%, respectively.

Enzyme-Linked Immunosorbent Assay↗
PubMed2002

Enhancement of the chemoprotective enzymes glucuronosyl transferase and glutathione transferase in specific organs of the rat by the coffee components kahweol and cafestol.

The coffee components kahweol and cafestol (K/C) have been reported to protect the colon and other organs of the rat against the formation of DNA adducts by 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine (PhIP) and aflatoxin B1. PhIP is a cooked-food mutagen to which significant human exposure and a role in colon cancer etiology are attributed, and, interestingly, such cancers appear to develop at a lower rate in consumers of coffees with high amounts of K/C. Earlier studies in rodent liver have shown that a key role in the chemopreventive effect of K/C is likely to be due to the potential of these compounds to induce the detoxification of xenobiotics by glutathione transferase (GST) and to enhance the synthesis of the corresponding co-factor glutathione. However, mutagens like PhIP may also be detoxified by UDP-glucuronosyl transferase (UDPGT) for which data are lacking regarding a potential effect of K/C. Therefore, in the present study, we investigated the effect of K/C on UDPGT and, concomitantly, we studied overall GST and the pattern of individual GST classes, particularly GST-theta;, which was not included in earlier experiments. In addition, we analyzed the organ-dependence of these potentially chemopreventive effects. K/C was fed to male F344 rats at 0.122% in the chow for 10 days. Enzyme activities in liver, kidney, lung, colon, salivary gland, pancreas, testis, heart and spleen were quantified using five characteristic substrates and the hepatic protein pattern of GST classes alpha, mu, and pi was studied with affinity chromatography/HPLC. Our study showed that K/C is not only capable of increasing overall GST and GST classes alpha, mu, and pi but also of enhancing UDGPT and GST-theta. All investigated K/C effects were strongest in liver and kidney, and some response was seen in lung and colon but none in the other organs. In summary, our results show that K/C treatment leads to a wide spectrum of increases in phase II detoxification enzymes. Notably, these effects occurred preferentially in the well perfused organs liver and kidney, which may thus not only contribute to local protection but also to anti-carcinogenesis in distant, less stimulated organs such as the colon.

Animals↗
PubMed1991

Purification and characterization of human muscle glutathione S-transferases: evidence that glutathione S-transferase zeta corresponds to a locus distinct from GST1, GST2, and GST3.

Human muscle glutathione S-transferase isozyme, GST zeta (pI 5.2) has been purified by three different methods using immunoaffinity chromatography, DEAE cellulose chromatography, and isoelectric focusing. GST zeta prepared by any of the three methods does not recognize antibodies raised against the alpha, mu, or pi class glutathione S-transferases of human tissues. GST zeta has a blocked N-terminus and its peptide fingerprints also indicate it to be distinct from the alpha, mu, or pi class isozymes. As compared to GSTs of alpha, mu, and pi classes, GST zeta displays higher activities toward t-stilbene oxide and Leukotriene A4 methyl ester. GST zeta also expresses GSH-peroxidase activity toward hydrogen peroxide. The Kms of GST zeta for CDNB and GSH were comparable to those reported for other human GSTs but its Vmax for CDNB, 7620 mol/mol/min, was found to be considerably higher than that reported for other human GSTs. The kinetics of inhibition of GST zeta by hematin, bile acids, and other inhibitors also indicate that it was distinct from the three classes of GST isozymes. These studies suggest that GST zeta corresponds to a locus distinct from GST1, GST2, and GST3 and probably corresponds to the GST4 locus as suggested previously by Laisney et al. (1984, Human Genet. 68, 221-227). The results of peptide fingerprints and kinetic analysis indicate that as compared to the pi and alpha class isozymes, GST zeta has more structural and functional similarities with the mu class isozymes. Besides GST zeta several other GST isozymes belonging to pi and mu class have also been characterized in muscle. The pi class GST isozymes of muscle have considerable charge heterogeneity among them despite identical N-terminal sequences.

Amino Acid Sequence↗
PubMed1985

Differential induction of cytochrome P-450-dependent monooxygenase, epoxide hydrolase, glutathione transferase and UDP glucuronosyl transferase activities in the liver of the rainbow trout by beta-naphthoflavone or Clophen A50.

After administration of beta-naphthoflavone and Clophen A50 to juvenile rainbow trout, activities of hepatic cytochrome P-450-dependent deethylation of 7-ethoxyresorufin was increased 172- and 49-fold, respectively. Glutathione transferase activity towards 1-chloro 2,4 dinitrobenzene and UDP glucuronosyltransferase activities towards p-nitrophenol, 1-naphthol and testosterone were increased 1.4 to 3.0-fold by beta-naphthoflavone or Clophen A50. However, significant increases of the rate of glucuronidation of 1-naphthol by Clophen A50 and of testosterone by both Clophen A50 and beta-naphthoflavone were only determined when the activities were measured in digitonin activated microsomes. Epoxide hydrolase activity was not affected by beta-naphthoflavone or Clophen A50. The time course of induction of the various xenobiotic metabolizing enzymes exhibited different patterns. 7-Ethoxyresorufin-O-deethylase activity reached peak values 3 and 7 days after the administration of beta-naphthoflavone and Clophen A50, respectively. The rate of induction of glutathione transferase activity and UDP glucuronosyltransferase activities towards p-nitrophenol and 1-naphthol were relatively slow and did not reach distinct peak levels. These activities were still on maximum levels 4-6 weeks after the treatment. Glucuronidation of testosterone reached peak values 1 week after treatment with both beta-naphthoflavone and Clophen A50. The dissimilar patterns of induction of the cytochrome P-450-dependent activities and the various conjugation activities may indicate that these xenobiotic metabolizing enzymes are differently regulated in the rainbow trout liver.

Animals↗
PubMed1986

Evidence for the metabolism of mitozantrone by microsomal glutathione transferases and 3-methylcholanthrene-inducible glucuronosyl transferases.

The metabolism of mitozantrone, a chemotherapeutic agent used in the treatment of breast cancer, has been studied in vitro using rat liver subcellular fractions. This compound would appear to be metabolized by two interesting pathways. One involves conjugation with glucuronic acid, catalyzed most effectively by a 3-methylcholanthrene-inducible glucuronosyl transferase. The other pathway appears to be a glutathione conjugation reaction which requires prior metabolism by cytochrome P-450. The reaction with glutathione appears to be enzymatic as 1-chloro-2,4-dinitrobenzene was a potent inhibitor of this reaction. Liver cytosol did not enhance the microsomal rate of glutathione-conjugate formation, suggesting an important role for the microsomal glutathione transferases in the disposition of this compound. The relationship between these reactions and the mode of action of mitozantrone is discussed.

Animals↗
PubMed1982

Effects of defined synthetic phospholipids on glycosylation processes. Modifications of membrane-bound N-acetylglucosaminyl-transferase and solubilized sialyl-transferase activities.

In this paper, we study effects of phosphatidylcholine synthetic derivatives on two different glycosyltransferasic systems, a membranous mitochondrial N-acetylglucosaminyl-transferase and a solubilized microsomal sialyl-transferase. From all our results, we proved the strong inhibitory effect of lysophosphatidylcholines in these glycosylation processes. We investigated then the relationship between this inhibitory effect and the chemical structure of the studied phospholipids. From this work, it became obvious that the most important inhibitory effect is obtained with a molecule containing a long aliphatic side chain in sn-1 of glycerol, a carbon atom devoid of any large group in sn-2 and an hydrophilic part in sn-3 (specially choline).

Animals↗
PubMed2005

Chemical genetics identifies Rab geranylgeranyl transferase as an apoptotic target of farnesyl transferase inhibitors.

A chemical genetics approach identified a cellular target of several proapoptotic farnesyl transferase inhibitors (FTIs). Treatment with these FTIs caused p53-independent apoptosis in Caenorhabditis elegans, which was mimicked by knockdown of endosomal trafficking proteins, including Rab5, Rab7, the HOPS complex, and notably the enzyme Rab geranylgeranyl transferase (RabGGT). These FTIs were found to inhibit mammalian RabGGT with potencies that correlated with their proapoptotic activity. Knockdown of RabGGT induced apoptosis in mammalian cancer cell lines, and both RabGGT subunits were overexpressed in several tumor tissues. These findings validate RabGGT, and by extension endosomal function, as a therapeutically relevant target for modulation of apoptosis, and enhance our understanding of the mechanism of action of FTIs.

Alkyl and Aryl Transferases↗
PubMed2002

Genetic polymorphisms of glutathione S-transferase A1, the major glutathione S-transferase in human liver: consequences for enzyme expression and busulfan conjugation.

BACKGROUND: High-dose busulfan is widely used as part of conditioning regimens for patients who are undergoing hematopoietic stem cell or bone marrow transplantation. High plasma concentrations of busulfan have been linked to the occurrence of hepatic venoocclusive disease (VOD), a severe complication associated with a high mortality. Because conjugation with glutathione, the major route of biotransformation of busulfan, is predominantly catalyzed by the isozyme glutathione S-transferase A1 (GSTA1), we hypothesized that low expression or function of GSTA1 in liver caused by genetic polymorphisms may be the mechanism underlying VOD. METHODS: Immunoblot analysis of GSTA and measurement of busulfan-glutathione conjugation by liquid chromatography-mass spectrometry were performed in 48 normal human liver samples. To search for polymorphisms, the complete GSTA1 coding regions and the promoter fragment were sequenced. All results were compared by multivariate analysis. RESULTS: Absolute levels of GSTA protein and formation rates of busulfan-glutathione conjugate displayed a 7- and 8-fold range, from 240 to 1600 pmol/mg and 25 to 205 pmol/min per milligram of total cytosolic protein, respectively, and correlate (r2 = 0.49, P <.0001). A total of 8 single nucleotide polymorphisms (SNPs) of GSTA1 were identified, 1 of which was a silent mutation in exon 5 (A375G); all others were found in the promoter region. Haplotype analysis revealed the existence of 5 defined alleles. There was no significant relationship between any of the GSTA1 SNPs or haplotypes and either hepatic glutathione S-transferase A (GSTA) expression or GSTA1 function. CONCLUSIONS: The identified GSTA1 polymorphisms are not likely to be related to the VOD because they do not appear to be associated with changes in GSTA expression or function. Compared with other members of the GST family, GSTA1 displays surprisingly little variation.

Busulfan↗
PubMed1996

Activation of glutathione transferase P gene by lead requires glutathione transferase P enhancer I.

Glutathione transferase P (GST-P) is specifically induced in rat liver and kidney by lead cation. The increase of GST-P mRNA after lead administration is blocked by actinomycin D, suggesting that GST-P production by lead is regulated at the transcriptional level. To further determine which part of the flanking region of the GST-P gene has the lead-responsive cis-element in vivo, we utilized transgenic rats with five different constructs having GST-P and/or chloramphenicol acetyl-transferase coding sequence. We studied the effect of lead on these transgenic rats and on transfected NRK (normal rat kidney) cells and found that GST-P induction by lead is indeed regulated at the transcriptional level and that the GST-P enhancer I (GPEI) enhancer is an essential cis-element required for the activation of the GST-P gene by lead. GPEI consists of two AP-1 (c-Jun/c-Fos heterodimer) site-like sequences that are palindromically arranged and can bind AP-1, c-jun mRNA in the liver increased after lead administration and GST-P, and c-Jun had patchy expression in the same hepatocytes 24 h after lead exposure. These results suggest that activation of the GST-P gene by lead is mediated in major part by enhancer GPEI and that AP-1 may be involved at least partially. GPEI has been shown to have essential sequence information for the trans-activation of the GST-P gene during chemical hepatocarcinogenesis of the rat (Morimura, S., Suzuki, T., Hochi, S., Yuki, A., Nomura, K., Kitagawa, T., Nagatsu, I., Imagawa, M., and Muramatsu, M. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 2065-2068; Suzuki, T., Imagawa, M., Hirabayashi, M., Yuki, A., Hisatake, K., Nomura, K., Kitagawa, T., and Muramatsu, M. (1995) Cancer Res. 55, 2651-2655). The present study establishes that the same enhancer element does operate in the activation of the GST-P gene by lead regardless of the trans-activators involved.

Animals↗
PubMed2000

Human glutathione transferase T2-2 discloses some evolutionary strategies for optimization of substrate binding to the active site of glutathione transferases.

Rapid kinetic, spectroscopic, and potentiometric studies have been performed on human Theta class glutathione transferase T2-2 to dissect the mechanism of interaction of this enzyme with its natural substrate GSH. Theta class glutathione transferases are considered to be older than Alpha, Pi, and Mu classes in the evolutionary pathway. As in the more recently evolved GSTs, the activation of GSH in the human Theta enzyme proceeds by a forced deprotonation of the sulfhydryl group (pK(a) = 6.1). The thiol proton is released quantitatively in solution, but above pH 6.5, a protein residue acts as an internal base. Unlike Alpha, Mu, and Pi class isoenzymes, the GSH-binding mechanism occurs via a simple bimolecular reaction with k(on) and k(off) values at least hundred times lower (k(on) = (2.7 +/- 0.8) x 10(4) M(-1) s(-1), k(off) = 36 +/- 9 s(-1), at 37 degrees C). Replacement of Arg-107 by alanine, using site-directed mutagenesis, remarkably increases the pK(a) value of the bound GSH and modifies the substrate binding modality. Y107A mutant enzyme displays a mechanism and rate constants for GSH binding approaching those of Alpha, Mu, and Pi isoenzymes. Comparison of available crystallographic data for all these GSTs reveals an unexpected evolutionary trend in terms of flexibility, which provides a basis for understanding our experimental results.

Arginine↗
PubMed2006

Evaluation of tumour necrosis factor-alpha, soluble P-selectin, gamma-glutamyl transferase, glutathione S-transferase-pi and alpha-fetoprotein in patients with hepatocellular carcinoma before and during chemotherapy.

Hepatocellular carcinoma (HCC) is an environmentally related cancer, with both viral and chemical carcinogens involved in a multistage process. To date, it has been difficult to detect the asymptomatic precursor lesions in early HCC. Therefore, the majority of HCC patients are not amenable to therapy, as they are detected at late stages. To evaluate the significance of tumour necrosis factor-alpha (TNF-alpha), sP-selectin, gamma-glutamyl transferase (GGT), glutathione S-transferase-pi (GST) and alpha-fetoprotein (AFP) in the diagnosis and follow up of HCC patients during chemotherapy with adriamycin, 45 subjects (15 healthy volunteers, 15 with benign liver diseases and 15 HCC patients) are studied before and during chemotherapy (three cycles of intravenous adriamycin). HCC patients had significantly higher serum levels of TNF-alpha, sP-selectin, GGT, GST and AFP Serum levels of GGT and GST were significantly higher in HCC patients with poorly differentiated tumours than in patients with well- and moderately differentiated tumours. Treatment with adriamycin for three cycles produced a significant decrease in TNF-alpha, sP-selectin and GST. Thus, it is concluded that GST is a superior diagnostic indicator and may be a prognostic marker in HCC patients.

Antibiotics, Antineoplastic↗
PubMed1994

Hepatic and intestinal cytochrome P-450, glutathione-S-transferase and UDP-glucuronosyl transferase are affected by six types of dietary fiber in rats inoculated with human whole fecal flora.

The effects of six different sources of dietary fiber (inulin, wheat brain, carrot, cocoa, pea and oat fiber) on hepatic and intestinal cytochrome P-450 (EC 1.14.14.1), glutathione-S-transferase (GSH-T, EC 2.5.1.18) and UDP-glucuronosyl transferase (UDPG-T, EC 2.4.1.17) were studied using germ-free F344 rats subsequently inoculated with a human whole fecal flora. In the liver, the total concentration of P-450 was significantly lower in the wheat bran-fed group than in the carrot-fed group. The 2E1 form of P-450, involved in nitrosamine metabolism, was enhanced in the carrot-fed group compared with those fed most other types of fiber. Compared with the pea-fed group, rats fed cocoa had a lower constitutive 2C11 form and a higher 1A2 form. A very high concentration of small intestinal 1A1 form--involved in "toxication" reactions--was observed in rats fed cocoa. The specific activity of hepatic GSH-T was significantly higher in rats fed inulin than in all other groups, except the carrot-fed group. In the colon, GSH-T specific activity was twice as high in the oat-fed group as in the wheat bran-fed counterpart. Small intestinal GSH-T activity and hepatic and intestinal UDPG-T activities were unaffected by diet. Results are discussed in relation to potential health benefits.

Adult↗
PubMed1988

Age- and sex-related changes in epoxide hydrolase, UDP-glucuronosyl transferase, glutathione S-transferase, and PAPS sulphotransferase in Sprague-Dawley rats.

1. Age- and sex-related patterns in the activity of hepatic phase 2 conjugating enzymes have been studied in Sprague-Dawley (CD) rats. 2. Epoxide hydrolase activity with styrene oxide ranged from 75 to 346 nmol/min per g and increased with age in males, peaking at week 78. In females, activity remained constant, about 80 nmol/min per g. 3. UDP-glucuronosyl transferase activity with p-nitrophenol ranged from 480 to 1050 nmol/min per g; maximal activity was at week 39. Males had greater activity at weeks 12 to 39. Activity with chloramphenicol ranged from 3.8 to 10.3 nmol/min per g with no consistent age or sex relationship. 4. Glutathione S-transferase ranged from 9.5 to 23.6 mumol/min per g with p-nitrobenzyl chloride and from 29.1 to 66.8 mumol/min per g with 1-chloro-2,4-dinitrobenzene, peaking at week 51 with both substrates. Males had greater activity from weeks 12 to 78. 5. Reduced glutathione varied between 3.2 and 6.5 mumol/g, with males tending to have higher concentrations than females and older rats (greater than 39 weeks) having slightly lower concentrations. 6. PAPS sulphotransferase ranged from 190 to 338 nmol/min per g, with maximal activity at week 78 with no consistent sex-related differences.

Age Factors↗