QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Coffman, B. L. Articles by Tephly, T. R. Search for Related Content PubMed PubMed Citation Articles by Coffman, B. L. Articles by Tephly, T. R.

0090-9556/97/2501-0001-0004$02.00/0
DRUG METABOLISM AND DISPOSITION
Copyright © 1997 by The American Society for Pharmacology and Experimental Therapeutics
Vol. 25, No. 1

ACCELERATED COMMUNICATION
Human UGT2B7 Catalyzes Morphine Glucuronidation

Birgit L. Coffman, Gladys R. Rios, Christopher D. King, and Thomas R. Tephly

Department of Pharmacology, University of Iowa

	Abstract

Abstract Introduction Results Discussion References

A human UDP-glucuronosyltransferase (UGT) catalyzing the glucuronidation of morphine has been identified. A full length cDNA was isolated from a human liver cDNA library and found to be identical to the UGT2B7 form having a tyrosine at position 268. This cDNA was transfected into HK 293 cells, and stable expression was achieved. Cell homogenates and membrane preparations from HK 293 cells expressing UGT2B7 catalyzed the glucuronidation of morphine and other clinically significant opioid agonists, antagonists, and partial agonists. UGT2B7 catalyzed morphine glucuronidation at the 3- and 6-hydroxy positions and also mediated the formation of codeine-6-glucuronide from codeine. This represents the first demonstration of a UGT capable of catalyzing the glucuronidation of both the 3- and 6-positions of opioids. Since humans excrete morphine-3-glucuronide and morphine-6-glucuronide after morphine administration, it is likely that UGT2B7 is a major isoform in humans responsible for the metabolism of this important drug and its surrogates.

	Introduction

Abstract Introduction Results Discussion References

Glucuronide conjugation is an important metabolic process in which xenobiotics and endobiotics are converted to hydrophilic metabolites through the mediation of UGTs¹ (E.C. 2.4.1.17). UGTs are intrinsic membrane proteins of the endoplasmic reticulum and nuclear envelope of cells of liver and other organs, and are encoded by multiple genes of at least two families (1). After glucuronidation, conjugates are readily excreted by renal and hepatic mechanisms leading to rapid elimination of the aglycone from the body. At this time, >30 individual UGT isoforms have been identified either by cloning and expression or by purification procedures from hepatic microsomes. UGTs that are members of the UGT1 gene complex share common second through fifth exons, with at least seven separate exons encoding for specific proteins with unique N-terminal domains (2). In contrast, gene products of the UGT2 family are transcribed from unique genes. At least eight isozymes of the human UGT2 family have been identified (3), and the genes UGT2B4, UGT2B9, and UGT2B15 have been mapped to human chromosome 4 (4, 5).

Xenobiotics such as those of the opioid drug class are, in general, metabolized and excreted largely as glucuronides by the liver and kidney. Morphine is the best example of an opioid drug that is extensively glucuronidated. Morphine possesses hydroxy groups on the 3- and 6- positions of the molecule and both morphine-3-glucuronide and morphine-6-glucuronide are found in the urine of humans (6, 7), whereas codeine with a methoxy group on the 3-position is converted only to the 6-glucuronide.

A principal interest in this laboratory for many years has been the isolation and identification of the UGTs that catalyze the glucuronidation of opioids in rats and humans (8-10). We have recently shown that stably expressed human UGT1.1, often termed the major "bilirubin" UGT (11), reacts with high affinity and efficiency with the opioid partial agonist/antagonist, buprenorphine (12). Previous investigations by Miners et al.(13) and Wahlström et al.(14) suggested, that several isozymes mediate hepatic opioid glucuronidation in humans; however, no expressed human UGTs (other than UGT1.1) have been reported to participate in opioid glucuronidation.

This communication describes the cloning and expression of a cDNA encoding for a human liver microsomal UGT that catalyzes the glucuronidation of morphine and other opioids. Sequence analysis showed that the cDNA was identical to a human UGT, termed UGT2B7 variant (15), which had been shown previously to code for a UGT mediating glucuronidation of NSAIDs and certain forms of carboxylic acid-containing drugs. This UGT, UGT2B7, is likely to be the major isoform responsible for morphine glucuronidation in humans.

Materials and Methods

Chemicals. UDP-GlcUA (319 mCi/mmol) was purchased from ICN Pharmaceuticals (Irvine, CA). Morphine sulfate was acquired from Merck (Rahway, NJ). Morphine-3-glucuronide, morphine-6-glucuronide, and codeine-6-glucuronide were acquired from Research Biochemicals (Natick, MA). All aglycones and L--phosphatidylcholine (type XVI-E from egg yolk), dithiothreitol, and UDP-GlcUA were purchased from Sigma Chemical Co. (St. Louis, MO). Protein assay reagents were from Bio-Rad (Richmond, CA).

Screening of the cDNA Library. A human liver cDNA library in Bluescript SK (Stratagene, La Jolla, CA) was plated in XL1-Blue MRF cells. The library was screened by plaque hybridization with a full length rat liver cDNA, UGT2B1 (kindly supplied by Dr. Peter Mackenzie, Flinders Medical Centre, Bedford Park, South Australia, Australia). The probe was labeled with ³²P-dCTP by the nick-translation method following the protocol of the supplier (Boehringer Mannheim Biochemica, Indianapolis, IN), and hybridization was performed at 42°C in 50% formamide, 4.8 × standard saline citrate, 1 × Denhardt's solution, 10% dextran, and 0.1% SDS containing salmon testes DNA at 0.1 mg/ml. Bacteriophages that hybridized to the probe were isolated and purified.

Restriction enzyme analysis showed that one clone (HM1) contained a 2.2 kb pair insert. This clone was further characterized.

DNA Sequence Analysis. Analysis was performed by the DNA Facility, University of Iowa, using an Applied Biosystems 373 A Automatic DNA Sequencer. The HM1 insert was initially sequenced in the Bluescript plasmid using primers to the T3 and T7 promoters. Subsequently, oligonucleotides were synthesized (Genosys Biotechnologies, The Woodlands, TX) and used as primers to generate additional and overlapping DNA sequences until both strands were sequenced.

Expression of HM1 in Human Embryonic Kidney (HK 293) Cells. The HM1 insert was removed from Bluescript SK and was ligated into the BamH1/Xho1 site of the mammalian expression vector pcDNA3.1 (Invitrogen, San Diego, CA). This expression vector construct is referred to as pcDNA3-2B. The HK 293 cells were transfected using the calcium phosphate transfection method (16) and were grown in media containing geneticin (G418) (17). Cells were harvested after 1-4 passages of stable transfection for analysis of glucuronidation activity.

Glucuronidation Assays. Cells expressing pcDNA3-2B protein were resuspended in TBS containing 0.5 mM dithiothreitol and disrupted by freeze-thawing 3 times in liquid nitrogen before homogenization. Glucuronidation activity toward opioids [5 mM morphine (pH 8.4), 5 mM codeine (pH 7.7), 2 mM nalorphine (pH 8.4), 2 mM naloxone (pH 7.7), 2 mM naltrexone (pH 7.0), and 0.5 mM buprenorphine (pH 7.0)] was assayed using the method described by Puig and Tephly (9). Determination of the kinetic parameters for glucuronidation of opioids was performed on membrane preparations from cells expressing pcDNA3-2B protein, prepared as described by Battaglia et al. (18). Membrane preparations were frozen in aliquots. Membranes were resuspended in TBS containing 0.5 mM dithiothreitol and homogenized by hand in a Potter-Elvehjem homogenizer. The glucuronides of morphine-3, morphine-6, and codeine-6 were identified and quantified using a modified HPLC method as described by Yue et al. (19). For HPLC analysis of morphine-3-glucuronide, morphine-6-glucuronide, and codeine-6-glucuronide conjugates, the samples were eluted from the Sep-Pak C₁₈ cartridges with 2 ml of 15% acetonitrile in phosphate buffer at pH 2.1. Morphine-3-glucuronide and morphine-6-glucuronide or codeine-6-glucuronide standards were added to 400 µl of the eluent that was injected into the HPLC system and eluted with 25% acetonitrile in phosphate buffer (pH 2.1) and 1 mM SDS. The radioactivity eluted with the glucuronide standards was measured. Analysis of glucuronidation of nonopioids was conducted and analyzed as described by Green et al. (17).

	Results

Abstract Introduction Results Discussion References

Screening and Nucleotide Sequence of HM1. Pritchard et al. (20) has previous reported that rat liver UGT2B1 exhibited glucuronidation activity toward morphine. Therefore, a human liver cDNA library was screened with the full-length cDNA, UGT2B1. Of 27 cDNA clones identified, two were full-length clones. One of these clones (HM1) was characterized and found to be identical to the human UGT2B7 variant as reported by Jin et al. (15). The deduced amino acid sequence has a tyrosine in position 268 instead of a histidine, as reported by Ritter et al. (21). Because there is no knowledge of the relative abundance of the two forms, there seems to be no reason to term either form as a variant at this time. Thus, we have designated HM1 as UGT2B7(Y) and the histidine form as UGT2B7(H).

Expression of UGT2B7(Y) in HK293 Cells. Stably expressed UGT2B7(Y) catalyzes the glucuronidation of opioids (table 1), whereas opioid glucuronidation by vector-transfected and nontransfected HK293 cells was not detected. Of the opioids tested with stably expressed UGY2B7(Y), the glucuronidation rates for morphine, naloxone, and nalorphine were similar, whereas the rates for naltrexone and buprenorphine were <10% of that determined for morphine. The rates of codeine-6-glucuronidation were only ~ 1% of the rate of morphine glucuronidation.

View this table: [in this window] [in a new window]   TABLE 1 Glucuronidation of opioids by human UGT2B7(Y) expressed in HK 293 cells Rates were measured in homogenates of cells from 3 or 4 passages. Assays were conducted as described in Materials and Methods using the extraction procedure of Puig and Tephly (9). Incubation time was 60 min using 2 mM UDP-GlcUA and 100 µg protein.

Expressed UGT2B7(Y) had been shown previously to glucuronidate 4-hydroxyestrone and 4-hydroxyestradiol, and carboxylic acid-containing NSAIDs, such as ibuprofen and naproxen (15). Glucuronidation activities toward the four mentioned substrates were observed when the UGT2B7(Y) expressed in HK293 cells was studied using homogenate preparation (data not shown).

The HPLC chromatogram of the products from the glucuronidation of morphine by the stably expressed UGT2B7(Y) using [¹⁴C]UDP-GlcUA is shown in fig. 1. Carrier morphine-3-glucuronide and morphine-6-glucuronide were added to the incubation samples before HPLC analysis, and radioactivity coeluting with standards was measured. Both morphine-3-glucuronide and morphine-6-glucuronide were formed in reactions catalyzed by UGT2B7(Y). Preliminary results have also shown that expressed UGT2B7(H) also catalyzes morphine-3-glucuronide and morphine-6-glucuronidation (data not shown).² Likewise, the HPLC analysis of the glucuronidation of codeine showed that radioactivity eluted along with the codeine-6-glucuronide standard (data not shown). This is the first demonstration of a UGT catalyzing the formation of an opioid-6-glucuronide.

View larger version (16K): [in this window] [in a new window]   Fig. 1.   HPLC chromatogram of a preparation from an incubation of morphine with a homogenate of HK 293 cells stably expressing UGT2B7(Y). Experimental procedures are given in Materials and Methods. , Absorbance at 210 nm; , radioactivity dpm/1000.

Kinetic parameters were determined for the glucuronidation of morphine, codeine, nalorphine, and buprenorphine using membrane preparations from the HK293 cells expressing UGT2B7(Y) (table 2). Nalorphine and buprenorphine were found to produce substrate inhibition above 1.2 mM and 0.3 mM substrate, respectively. Buprenorphine and nalorphine are glucuronidated with higher efficiency than morphine, which is probably due to the increased length of the N-alkyl side chain of these opioids. The efficiency of codeine glucuronidation was 8 times less than that of morphine-6-glucuronidation.

View this table: [in this window] [in a new window]   TABLE 2 Kinetic parameters of glucuronide formation in a membrane preparation from HK 293 cells stably expressing UGT2B7(Y) Rates were measured using a single membrane preparation from cells after 3-4 passages. Assays were conducted as described in Materials and Methods at established optimum conditions for each substrate and 2 mM UDP-GlcUA. Formation of morphine-3-, morphine-6-, and codeine glucuronides was analyzed by the HPLC method, whereas formation of nalorphine and buprenorphine glucuronide was established using the extraction method of Puig and Tephly (9). Data represent the mean values obtained from two different determinations.

	Discussion

Abstract Introduction Results Discussion References

Morphine is metabolized in humans to morphine-3-glucuronide and morphine-6-glucuronide; but, until now, no human UGT has been identified to catalyze the formation of morphine-3-glucuronide and morphine-6-glucuronide with significant efficiency. UGT1.1, which also catalyzes opioid glucuronidation (12), does not catalyze the formation of morphine-6-glucuronide (unpublished data). The ratio of V_max for the formation of morphine-3-glucuronide vs. morphine-6-glucuronide by the expressed UGT2B7(Y) was found to be similar to ratios reported for human liver microsomes (~ 7:1) (19, 22). These data suggest that the UGT2B7(Y) represents the major human morphine UGT catalyzing the glucuronidation of the 3-OH and the 6-OH positions in opioids. Morphine-6-glucuronide has been shown to be a potent analgesic in clinical studies in human subjects, and the analgesic properties of morphine in humans are enhanced by the action of morphine-6-glucuronide (23). Morphine-3-glucuronide, in contrast, has no analgesic effect but shows enhanced excitatory activity by a nonopioid mechanism (24). It has been suggested that certain adverse effects of morphine in humans is due to the morphine-3-glucuronide formed. Thus, glucuronidation processes in the case of opioid pharmacology (e.g. morphine) may lead to potentially enhanced drug action or adverse effects not usually considered in the process of glucuronidation of most drugs.

1,4-Benzodiazepine derivatives, such as diazepam and halazepam, are converted in vivo to oxazepam, an active metabolite that is subsequently excreted as the pharmacologically inactive diasterometric oxazepam glucuronide. Based on inhibition studies, Patel et al. (25) have suggested that the S and R forms of oxazepam are glucuronidated by different UGT isozymes, and that UGT2B7 is the enzyme catalyzing the formation of S-oxazepam glucuronide. Patel et al. (26) also have found that 10% of a population had a significantly lower ratio of S- to R-glucuronide metabolites. This result correlated with the results of an in vitro study using microsomes from human livers, where 10% of the livers displayed an abnormal high K_M for the formation of the S-glucuronide, but no differences were found for K_M for the R-glucuronide formation. These investigators speculated that the differences could be caused by a polymorphism in the UGT2B7 gene, yet the only difference in the proteins of UGT2B7(H) and UGT2B7(Y) is a histidine instead of a tyrosine at the 268 position. This amino acid difference does not seem to alter the glucuronidation ratio of morphine-3-glucuronide to morphine-6-glucuronide.² Whether the difference in one amino acid affects the glucuronidation of substrates other than morphine is unknown at the present time. In addition, the question remains as to which UGT2B7 form is predominant in the human population.

Buprenorphine and naltrexone are antagonists that are under investigation as potential drugs for the treatment of opioid (27) and alcohol (28) abuse, respectively. Stably expressed human UGT1.1 also catalyzes the glucuronidation of opioids, in addition to bilirubin. This isoform reacts with high affinity toward buprenorphine, but exhibits a low efficiency of glucuronidation toward naltrexone and nalorphine (12), which may explain why liver microsomes from Crigler-Najjar type I patients, who do not express an active UGT1.1 due to a defect in the first exon of the UGT1 gene, glucuronidate buprenorphine at low rates (12). Naltrexone is glucuronidated at normal rates in Crigler-Najjar patients (12) most likely because UGT2B7 is the major isoform involved in its glucuronidation. However, the use of naltrexone or buprenorphine in patients with perturbation of liver function, as in alcohol addiction, might pose some problems dependent on the adequacy of the UGT2B7, UGT1.1, and UDP-GlcUA levels in such patients. Moreover, possible drug-endobiotic interaction must be considered when morphine is administered with such substrates that also interact with UGT2B7 (e.g. catechol estrogens). Drug-drug interactions should likewise be considered, because UGT2B7 is a major isoform catalyzing NSAID and benzodiazepine glucuronidation. Further studies on the substrate specificity and kinetic analysis for UGT2B7(Y) and UGT2B7(H) need to be investigated to identify possible drug-endobiotic and/or drug-drug interactions.

	Footnotes

Received September 19, 1996; accepted October 28, 1996.

   This research was supported by the National Institutes of Health Grant GM26221.

²   T. R. Tephly et al., unpublished data.

Send reprint requests to: Dr. Thomas R. Tephly, 2-459 Bowen Science Building, Department of Pharmacology, University of Iowa, Iowa City, IA 52242.

	Abbreviations

Abbreviations used are: UGT, UDP-glucuronosyltransferase; NSAID, nonsteroidal anti-inflammatory drug; UDP-GlcUA, UDP-glucuronic acid; SDS, sodium dodecyl sulfate; TBS, 10mM Tris, 0.9% NaCl, pH 7.4; OH, hydroxy.

	References

Abstract Introduction Results Discussion References

1.	D. J. Clarke and B. Burchell: The uridine diphosphate glucuronosyltransferase multigene family: function and regulation. In "Handbook of Experimental Pharmacology, Volume 112. Conjugation-Deconjugation Reactions in Drug Metabolism and Toxicity" (F.C. Kauffman, ed.), pp. 3-43. Springer-Verlag, Berlin, 1994.
2.	J. K. Ritter, F. Chen, Y. Y. Sheen, H. M. Tran, S. Kimura, M. T. Yeatman, and I. S. Owens: A novel complex locus UGT1 encodes human bilirubin, phenol, and other UDP-glucuronosyltransferase isoenzymes with identical carboxyl termini. J. Biol. Chem.  267, 3257-3261 (1992)[Abstract/Free Full Text].
3.	B. Burchell, C. H. Brierley, and D. Rance: Specificity of human UDP-glucuronosyltransferases and xenobiotic glucuronidation. Life Sci.  57, 1819-1831 (1995)[Medline].
4.	G. Monaghan, S. Povey, B. Burchell, and M. Boxer: Localization of a bile acid UDP-glucuronosyltransferase gene (UGT2B4) to chromosome 4 using the polymerase chain reaction. Genomics  13, 908-909 (1992)[Medline].
5.	G. Monaghan, D. J. Clarke, S. Povey, C. G. See, M. Boxer, and B. Burchell: Isolation of a human YAC contig encompassing a cluster of UGT2 genes and its regional localization to chromosome 4q3. Genomics  23, 496-499 (1994)[Medline].
6.	K. Oguri, S. Ida, H. Yoshimura, and H. Tsukamoto: Metabolism of drugs LXIX. Studies on the urinary metabolites of morphine in several mammalian species. Chem. Pharm. Bull.  18, 2414-2419 (1970).
7.	S. Y. Yeh, G. W. Gorodetsky, and H. A. Krebs: Isolation and identification of morphine-3 and 6-glucuronides, morphine 3,6 diglucuronide, morphine 3-ethereal sulfate, normorphine and normorphine 6-glucuronide as morphine metabolites in humans. J. Pharm. Sci.  66, 1288-1293 (1977)[Medline].
8.	E. del Villar, E. Sanchez, A. P. Autor, and T. R. Tephly: Morphine metabolism. III. Solubilization and separation of morphine and p-nitrophenol uridine-diphosphateglucuronosyltransferase. Mol. Pharmacol.  11, 236-240 (1975)[Abstract/Free Full Text].
9.	J. F. Puig and T. R. Tephly: Isolation and purification of rat liver morphine UDP-glucuronosyltransferase. Mol. Pharmacol.  30, 558-565 (1986)[Abstract].
10.	B. L. Coffman, G. R. Rios, and T. R. Tephly: Purification and properties of two rat liver phenobarbital-inducible UDP-glucuronosyltransferases that catalyze the glucuronidation of opioids. Drug Metab. Disp.  24, 329-333 (1996)[Abstract].
11.	P. J. Bosma, J. Seppen, B. Goldhoorn, C. Bakker, R. P. J. Oude Elferink, J. R. Chowdhury, N. R. Chowdhury, and P. L. M. Jansen: Bilirubin UDP-glucuronosyltransferase 1 is the only relevant bilirubin glucuronidating isoform in man. J. Biol. Chem.  269, 17960-17964 (1994)[Abstract/Free Full Text].
12.	C. D. King, M. D. Green, B. L. Coffman, I. S. Owens, W. P. Bishop, and T. R. Tephly: The glucuronidation of exogenous and endogenous compounds by stably expressed rat and human UDP-glucuronosyltransferases 1.1. Arch. Biochem. Biophys.  332, 92-100 (1996)[Medline].
13.	J. O. Miners, K. J. Lillywhite, and D. J. Birkett: In vitro evidence for the involvement of at least two forms of human liver UDP-glucuronosyltransferase in morphine 3-glucuronidation. Biochem. Pharmacol.  37, 2839-2845 (1988)[Medline].
14.	A. Wahlström, G. M. Pacifici, and B. Lindstr: m, L. Hammar, and A. Rane: Human liver morphine UDP-glucuronyltransferase enantioselectivity and inhibition by opioid congeners and oxazepam. Br. J. Pharmacol.  94, 864-870 (1988)[Medline].
15.	C. Jin, J. O. Miners, K. J. Lillywhite, and P. I. Mackenzie: Complementary deoxyribonucleic acid cloning and expression of a human liver uridine diphosphate-glucuronosyltransferase glucuronidating carboxyl acid-containing drugs. J. Pharmacol. Exp. Ther.  264, 475-479 (1993)[Abstract/Free Full Text].
16.	C. A. Chen and H. Okayama: Calcium phosphate-mediated gene transfer: a highly efficient system for stably transforming cells with plasmid DNA. Biotechniques  6, 632-638 (1988)[Medline].
17.	M. D. Green, E. M. Oturu, and T. R. Tephly: Stable expression of a human liver UDP-glucuronosyltransferase (UGT2B15) with activity toward steroid and xenobiotic substrates. Drug Metab. Dispos.  22, 799-805 (1994)[Abstract].
18.	E. Battaglia, C. Senay, S. Fournel-Gigleux, R. Herber, G. Siest, and J. Magdalou: The chemical modification of human liver UDP-glucuronosyltransferase UGT1*6 reveals the involvement of a carboxyl group in catalysis. FEBS Lett.  346, 146-150 (1994)[Medline].
19.	Q. Yue, C. von Bahr, I. Odar-Cederlöf, and J. Säwe: Glucuronidation of codeine and morphine in human liver and kidney microsomes: effect of inhibition. Pharmacol. Toxicol.  66, 221-226 (1990)[Medline].
20.	M. Pritchard, S. Fournel-Gigleux, G. Siest, P. Mackenzie, and J. Magdalou: A recombinant phenobarbital-inducible rat liver (UDP-glucuronosyltransferase 2B1) stably expressed in V79 cells catalyzes the glucuronidation of morphine, phenols and carboxylic acids. Mol. Pharmacol.  45, 42-50 (1994)[Abstract].
21.	J. K. Ritter, Y. Y. Sheen, and I. S. Owens: Cloning and expression of human liver UDP-glucuronosyltransferase in COS-1 cells. J. Biol. Chem.  265, 7900-7906 (1989)[Abstract/Free Full Text].
22.	A. Rane, J. Säwe, G. M. Pacifici, J.-O. Svensson, and K. Lager: Regioselective glucuronidation of morphine and interactions with benzodiazepines in human liver. Adv. Pain Res. Ther.  8, 57-64 (1986).
23.	R. Osborne, S. Joel, D. Trew, and M. Slevin: Morphine and metabolite behaviour after different routes of morphine administration: demonstration of the importance of the active metabolite morphine-6-glucuronide. Clin. Pharmacol. Ther.  47, 12-19 (1990)[Medline].
24.	Y. Hashigushi, P. E. Molina, and N. N. Abumrad: Morphine-3-glucuronide: hyperglycemic and neuroendocrine potentiating effects. Brain Res.  694, 13-20 (1995)[Medline].
25.	M. Patel, B. K. Tang, and W. Kalow: (S) oxazepam is inhibited by ketoprofen and other substrates of UGT2B7. Pharmacogenetics  5, 43-49 (1995)[Medline].
26.	M. Patel, B. K. Tang, D. M. Grant, and W. Kalow: Interindividual variability in the glucuronidation of (S) oxazepam contrasted with that of (R) oxazepam. Pharmacogenetics  5, 287-297 (1995)[Medline].
27.	A. Cowan and J. W. Lewis (eds.): "Buprenorphine: Combating Drug Abuse with a Unique Opioid." Wiley-Liss, New York, 1995.
28.	D. Davidson, R. Swift, and E. Fitz: Naltrexone increases the latency to drink alcohol in the social drinkers. Alcohol. Clin. Exp. Res.  20, 732-739 (1996)[Medline].

---

Copyright © 1997 by The American Society for Pharmacology and Experimental Therapeutics

This article has been cited by other articles:

				S. Ohno, K. Kawana, and S. Nakajin Contribution of UDP-Glucuronosyltransferase 1A1 and 1A8 to Morphine-6-Glucuronidation and Its Kinetic Properties Drug Metab. Dispos., April 1, 2008; 36(4): 688 - 694. [Abstract] [Full Text] [PDF]

				A. Zielinska, C. F. Lichti, S. Bratton, N. C. Mitchell, A. Gallus-Zawada, V.-H. Le, M. Finel, G. P. Miller, A. Radominska-Pandya, and J. H. Moran Glucuronidation of Monohydroxylated Warfarin Metabolites by Human Liver Microsomes and Human Recombinant UDP-Glucuronosyltransferases J. Pharmacol. Exp. Ther., January 1, 2008; 324(1): 139 - 148. [Abstract] [Full Text] [PDF]

				K. van de Wetering, N. Zelcer, A. Kuil, W. Feddema, M. Hillebrand, M. L. H. Vlaming, A. H. Schinkel, J. H. Beijnen, and P. Borst Multidrug Resistance Proteins 2 and 3 Provide Alternative Routes for Hepatic Excretion of Morphine-Glucuronides Mol. Pharmacol., August 1, 2007; 72(2): 387 - 394. [Abstract] [Full Text] [PDF]

				B. J. Dean, S. Chang, M. V. S. Elipe, Y.-Q. Xia, M. Braun, E. Soli, Y. Zhao, R. B. Franklin, and B. Karanam Metabolism of MK-0524, a Prostaglandin D2 Receptor 1 Antagonist, in Microsomes and Hepatocytes from Preclinical Species and Humans Drug Metab. Dispos., February 1, 2007; 35(2): 283 - 292. [Abstract] [Full Text] [PDF]

				M. J. Zaya, R. N. Hines, and J. C. Stevens Epirubicin Glucuronidation and UGT2B7 Developmental Expression Drug Metab. Dispos., December 1, 2006; 34(12): 2097 - 2101. [Abstract] [Full Text] [PDF]

				S. Takeda, Y. Kitajima, Y. Ishii, Y. Nishimura, P. I. Mackenzie, K. Oguri, and H. Yamada INHIBITION OF UDP-GLUCURONOSYLTRANSFERASE 2B7-CATALYZED MORPHINE GLUCURONIDATION BY KETOCONAZOLE: DUAL MECHANISMS INVOLVING A NOVEL NONCOMPETITIVE MODE Drug Metab. Dispos., August 1, 2006; 34(8): 1277 - 1282. [Abstract] [Full Text] [PDF]

				L. Xu, D. M. Krenitsky, A. M. Seacat, J. L. Butenhoff, T. R. Tephly, and M. W. Anders N-GLUCURONIDATION OF PERFLUOROOCTANESULFONAMIDE BY HUMAN, RAT, DOG, AND MONKEY LIVER MICROSOMES AND BY EXPRESSED RAT AND HUMAN UDP-GLUCURONOSYLTRANSFERASES Drug Metab. Dispos., August 1, 2006; 34(8): 1406 - 1410. [Abstract] [Full Text] [PDF]

				J. R. Ross, J. Riley, C. Quigley, and K. I. Welsh Clinical Pharmacology and Pharmacotherapy of Opioid Switching in Cancer Patients Oncologist, July 1, 2006; 11(7): 765 - 773. [Abstract] [Full Text] [PDF]

				M. M. Doherty, K. Poon, C. Tsang, and K. S. Pang Transport Is Not Rate-Limiting in Morphine Glucuronidation in the Single-Pass Perfused Rat Liver Preparation J. Pharmacol. Exp. Ther., May 1, 2006; 317(2): 890 - 900. [Abstract] [Full Text] [PDF]

				M. Garland, K. M. Abildskov, S. Taylor, K. Benzeroual, C. S. Caspersen, S. E. Arroyo, T.-w. Kiu, B. Reznik, P. Weldy, S. S. Daniel, et al. FETAL MORPHINE METABOLISM AND CLEARANCE ARE CONSTANT DURING LATE GESTATION Drug Metab. Dispos., April 1, 2006; 34(4): 636 - 646. [Abstract] [Full Text] [PDF]

				E. M. Peckham and J. R. Traynor Comparison of the Antinociceptive Response to Morphine and Morphine-Like Compounds in Male and Female Sprague-Dawley Rats J. Pharmacol. Exp. Ther., March 1, 2006; 316(3): 1195 - 1201. [Abstract] [Full Text] [PDF]

				S. Chouinard, M. Tessier, G. Vernouillet, S. Gauthier, F. Labrie, O. Barbier, and A. Belanger Inactivation of the Pure Antiestrogen Fulvestrant and Other Synthetic Estrogen Molecules by UDP-Glucuronosyltransferase 1A Enzymes Expressed in Breast Tissue Mol. Pharmacol., March 1, 2006; 69(3): 908 - 920. [Abstract] [Full Text] [PDF]

				G. E. Kuehl, J. W. Lampe, J. D. Potter, and J. Bigler GLUCURONIDATION OF NONSTEROIDAL ANTI-INFLAMMATORY DRUGS: IDENTIFYING THE ENZYMES RESPONSIBLE IN HUMAN LIVER MICROSOMES Drug Metab. Dispos., July 1, 2005; 33(7): 1027 - 1035. [Abstract] [Full Text] [PDF]

				M. Tachibana, M. Tanaka, Y. Masubuchi, and T. Horie ACYL GLUCURONIDATION OF FLUOROQUINOLONE ANTIBIOTICS BY THE UDP-GLUCURONOSYLTRANSFERASE 1A SUBFAMILY IN HUMAN LIVER MICROSOMES Drug Metab. Dispos., June 1, 2005; 33(6): 803 - 811. [Abstract] [Full Text] [PDF]

				N. Zelcer, K. van de Wetering, M. Hillebrand, E. Sarton, A. Kuil, P. R. Wielinga, T. Tephly, A. Dahan, J. H. Beijnen, and P. Borst Mice lacking multidrug resistance protein 3 show altered morphine pharmacokinetics and morphine-6-glucuronide antinociception PNAS, May 17, 2005; 102(20): 7274 - 7279. [Abstract] [Full Text] [PDF]

				T. O. Lankisch, A. Vogel, S. Eilermann, A. Fiebeler, B. Krone, A. Barut, M. P. Manns, and C. P. Strassburg Identification and Characterization of a Functional TATA Box Polymorphism of the UDP Glucuronosyltransferase 1A7 Gene Mol. Pharmacol., May 1, 2005; 67(5): 1732 - 1739. [Abstract] [Full Text] [PDF]

				H. Kaji and T. Kume REGIOSELECTIVE GLUCURONIDATION OF DENOPAMINE: MARKED SPECIES DIFFERENCES AND IDENTIFICATION OF HUMAN UDP-GLUCURONOSYLTRANSFERASE ISOFORM Drug Metab. Dispos., March 1, 2005; 33(3): 403 - 412. [Abstract] [Full Text] [PDF]

				S. Takeda, Y. Ishii, M. Iwanaga, P. I. Mackenzie, K. Nagata, Y. Yamazoe, K. Oguri, and H. Yamada Modulation of UDP-Glucuronosyltransferase Function by Cytochrome P450: Evidence for the Alteration of UGT2B7-Catalyzed Glucuronidation of Morphine by CYP3A4 Mol. Pharmacol., March 1, 2005; 67(3): 665 - 672. [Abstract] [Full Text] [PDF]

				G. H. Wynn, K. L. Cozza, M. J. Zapor, G. W. Wortmann, and S. C. Armstrong Antiretrovirals, Part III: Antiretrovirals and Drugs of Abuse Psychosomatics, February 1, 2005; 46(1): 79 - 87. [Abstract] [Full Text] [PDF]

				H. Yamanaka, M. Nakajima, M. Katoh, A. Kanoh, O. Tamura, H. Ishibashi, and T. Yokoi TRANS-3'-HYDROXYCOTININE O- AND N-GLUCURONIDATIONS IN HUMAN LIVER MICROSOMES Drug Metab. Dispos., January 1, 2005; 33(1): 23 - 30. [Abstract] [Full Text] [PDF]

				M. Garland, K. M. Abildskov, T.-w. Kiu, S. S. Daniel, and R. I. Stark THE CONTRIBUTION OF FETAL METABOLISM TO THE DISPOSITION OF MORPHINE Drug Metab. Dispos., January 1, 2005; 33(1): 68 - 76. [Abstract] [Full Text] [PDF]

				A. G. Staines, M. W. H. Coughtrie, and B. Burchell N-Glucuronidation of Carbamazepine in Human Tissues Is Mediated by UGT2B7 J. Pharmacol. Exp. Ther., December 1, 2004; 311(3): 1131 - 1137. [Abstract] [Full Text] [PDF]

				J. M. Little, M. Kurkela, J. Sonka, S. Jantti, R. Ketola, S. Bratton, M. Finel, and A. Radominska-Pandya Glucuronidation of oxidized fatty acids and prostaglandins B1 and E2 by human hepatic and recombinant UDP-glucuronosyltransferases J. Lipid Res., September 1, 2004; 45(9): 1694 - 1703. [Abstract] [Full Text] [PDF]

				D. Zhang, W. Zhao, V. A. Roongta, J. G. Mitroka, L. J. Klunk, and M. Zhu AMIDE N-GLUCURONIDATION OF MAXIPOST CATALYZED BY UDP-GLUCURONOSYLTRANSFERASE 2B7 IN HUMANS Drug Metab. Dispos., May 1, 2004; 32(5): 545 - 551. [Abstract] [Full Text] [PDF]

				S. Nagar, R. P. Remmel, R. P. Hebbel, and C. L. Zimmerman METABOLISM OF OPIOIDS IS ALTERED IN LIVER MICROSOMES OF SICKLE CELL TRANSGENIC MICE Drug Metab. Dispos., January 1, 2004; 32(1): 98 - 104. [Abstract] [Full Text] [PDF]

				M. G. Soars, D. M. Petullo, J. A. Eckstein, S. C. Kasper, and S. A. Wrighton AN ASSESSMENT OF UDP-GLUCURONOSYLTRANSFERASE INDUCTION USING PRIMARY HUMAN HEPATOCYTES Drug Metab. Dispos., January 1, 2004; 32(1): 140 - 148. [Abstract] [Full Text] [PDF]

				A. N. Stone, P. I. Mackenzie, A. Galetin, J. B. Houston, and J. O. Miners ISOFORM SELECTIVITY AND KINETICS OF MORPHINE 3- AND 6-GLUCURONIDATION BY HUMAN UDP-GLUCURONOSYLTRANSFERASES: EVIDENCE FOR ATYPICAL GLUCURONIDATION KINETICS BY UGT2B7 Drug Metab. Dispos., September 1, 2003; 31(9): 1086 - 1089. [Abstract] [Full Text] [PDF]

				M. H. Court, S. Krishnaswamy, Q. Hao, S. X. Duan, C. J. Patten, L. L. von Moltke, and D. J. Greenblatt EVALUATION OF 3'-AZIDO-3'-DEOXYTHYMIDINE, MORPHINE, AND CODEINE AS PROBE SUBSTRATES FOR UDP-GLUCURONOSYLTRANSFERASE 2B7 (UGT2B7) IN HUMAN LIVER MICROSOMES: SPECIFICITY AND INFLUENCE OF THE UGT2B7*2 POLYMORPHISM Drug Metab. Dispos., September 1, 2003; 31(9): 1125 - 1133. [Abstract] [Full Text] [PDF]

				Y. Watanabe, M. Nakajima, N. Ohashi, T. Kume, and T. Yokoi Glucuronidation of Etoposide in Human Liver Microsomes Is Specifically Catalyzed by UDP-Glucuronosyltransferase 1A1 Drug Metab. Dispos., May 1, 2003; 31(5): 589 - 595. [Abstract] [Full Text] [PDF]

				J. Y. Zhang, J. Zhan, C. S. Cook, R. M. Ings, and A. P. Breau Involvement of Human UGT2B7 and 2B15 in Rofecoxib Metabolism Drug Metab. Dispos., May 1, 2003; 31(5): 652 - 658. [Abstract] [Full Text] [PDF]

				D. Turgeon, J.-S. Carrier, S. Chouinard, and A. Belanger Glucuronidation Activity of the UGT2B17 Enzyme toward Xenobiotics Drug Metab. Dispos., May 1, 2003; 31(5): 670 - 676. [Abstract] [Full Text] [PDF]

				T. Hirota, I. Ieiri, H. Takane, H. Sano, K. Kawamoto, H. Aono, A. Yamasaki, H. Takeuchi, M. Masada, E. Shimizu, et al. Sequence Variability and Candidate Gene Analysis in Two Cancer Patients with Complex Clinical Outcomes During Morphine Therapy Drug Metab. Dispos., May 1, 2003; 31(5): 677 - 680. [Abstract] [Full Text] [PDF]

				L. V. Iyer, M. N. Ho, W. M. Shinn, W. W. Bradford, M. J. Tanga, S. S. Nath, and C. E. Green Glucuronidation of 1'-Hydroxyestragole (1'-HE) by Human UDP-Glucuronosyltransferases UGT2B7 and UGT1A9 Toxicol. Sci., May 1, 2003; 73(1): 36 - 43. [Abstract] [Full Text] [PDF]

				S. C. Armstrong and K. L. Cozza Pharmacokinetic Drug Interactions of Morphine, Codeine, and Their Derivatives: Theory and Clinical Reality, Part I Psychosomatics, April 1, 2003; 44(2): 167 - 171. [Abstract] [Full Text] [PDF]

				B. L. Coffman, W. R. Kearney, S. Goldsmith, B. M. Knosp, and T. R. Tephly Opioids Bind to the Amino Acids 84 to 118 of UDP-Glucuronosyltransferase UGT2B7 Mol. Pharmacol., February 1, 2003; 63(2): 283 - 288. [Abstract] [Full Text] [PDF]

				C. Tang, J. H. Hochman, B. Ma, R. Subramanian, and K. P. Vyas Acyl Glucuronidation and Glucosidation of a New and Selective Endothelin ETA Receptor Antagonist in Human Liver Microsomes Drug Metab. Dispos., January 1, 2003; 31(1): 37 - 45. [Abstract] [Full Text] [PDF]

				G. R. Rios and T. R. Tephly Inhibition and Active Sites of UDP-Glucuronosyltransferases 2B7 and 1A1. Drug Metab. Dispos., December 1, 2002; 30(12): 1364 - 1367. [Abstract] [Full Text] [PDF]

				Y. Watanabe, M. Nakajima, and T. Yokoi Troglitazone Glucuronidation in Human Liver and Intestine Microsomes: High Catalytic Activity of UGT1A8 and UGT1A10 Drug Metab. Dispos., December 1, 2002; 30(12): 1462 - 1469. [Abstract] [Full Text] [PDF]

				M. Nakajima, E. Tanaka, J.-T. Kwon, and T. Yokoi Characterization of Nicotine and Cotinine N-Glucuronidations in Human Liver Microsomes Drug Metab. Dispos., December 1, 2002; 30(12): 1484 - 1490. [Abstract] [Full Text] [PDF]

				M. Nakajima, N. Sakata, N. Ohashi, T. Kume, and T. Yokoi Involvement of Multiple UDP-glucuronosyltransferase 1A Isoforms in Glucuronidation of 5-(4'-hydroxyphenyl)-5-phenylhydantoin in Human Liver Microsomes Drug Metab. Dispos., November 1, 2002; 30(11): 1250 - 1256. [Abstract] [Full Text] [PDF]

				J. A. Williams, B. J. Ring, V. E. Cantrell, K. Campanale, D. R. Jones, S. D. Hall, and S. A. Wrighton Differential Modulation of UDP-Glucuronosyltransferase 1A1 (UGT1A1)-Catalyzed Estradiol-3-glucuronidation by the Addition of UGT1A1 Substrates and Other Compounds to Human Liver Microsomes Drug Metab. Dispos., November 1, 2002; 30(11): 1266 - 1273. [Abstract] [Full Text] [PDF]

				J. M. Little, L. Williams, J. Xu, and A. Radominska-Pandya Glucuronidation of the Dietary Fatty Acids, Phytanic Acid and Docosahexaenoic Acid, by Human UDP-Glucuronosyltransferases Drug Metab. Dispos., May 1, 2002; 30(5): 531 - 533. [Abstract] [Full Text] [PDF]

				C P Strassburg, A Strassburg, S Kneip, A Barut, R H Tukey, B Rodeck, and M P Manns Developmental aspects of human hepatic drug glucuronidation in young children and adults Gut, February 1, 2002; 50(2): 259 - 265. [Abstract] [Full Text] [PDF]

				Y. Ishii, A. Miyoshi, R. Watanabe, K. Tsuruda, M. Tsuda, Y. Yamaguchi-Nagamatsu, K. Yoshisue, M. Tanaka, D. Maji, S. Ohgiya, et al. Simultaneous Expression of Guinea Pig UDP-Glucuronosyltransferase 2B21 and 2B22 in COS-7 Cells enhances UDP-Glucuronosyltransferase 2B21-Catalyzed Morphine-6-Glucuronide Formation Mol. Pharmacol., November 1, 2001; 60(5): 1040 - 1048. [Abstract] [Full Text]

				B. L. Coffman, W. R. Kearney, M. D. Green, R. G. Lowery, and T. R. Tephly Analysis of Opioid Binding to UDP-Glucuronosyltransferase 2B7 Fusion Proteins Using Nuclear Magnetic Resonance Spectroscopy Mol. Pharmacol., June 1, 2001; 59(6): 1464 - 1469. [Abstract] [Full Text]

				C. King, W. Tang, J. Ngui, T. Tephly, and M. Braun Characterization of Rat and Human UDP-Glucuronosyltransferases Responsible for the in Vitro Glucuronidation of Diclofenac Toxicol. Sci., May 1, 2001; 61(1): 49 - 53. [Abstract] [Full Text] [PDF]

				A. R. Jude, J. M. Little, A. W. Bull, I. Podgorski, and A. Radominska-Pandya 13-Hydroxy- and 13-Oxooctadecadienoic acids: Novel Substrates for Human UDP-Glucuronosyltransferases Drug Metab. Dispos., April 13, 2001; 29(5): 652 - 655. [Abstract] [Full Text]

				F. Innocenti, L. Iyer, J. Ramírez, M. D. Green, and M. J. Ratain Epirubicin Glucuronidation Is Catalyzed by Human UDP-Glucuronosyltransferase 2B7 Drug Metab. Dispos., April 13, 2001; 29(5): 686 - 692. [Abstract] [Full Text]

				O. Barbier, C. Albert, I. Martineau, M. Vallée, K. High, F. Labrie, D. W. Hum, C. Labrie, and A. Bélanger Glucuronidation of the Nonsteroidal Antiestrogen EM-652 (SCH 57068), by Human and Monkey Steroid Conjugating UDP-Glucuronosyltransferase Enzymes Mol. Pharmacol., March 1, 2001; 59(3): 636 - 645. [Abstract] [Full Text]

				B. T. Ethell, K. Beaumont, D. J. Rance, and B. Burchell Use of Cloned and Expressed Human UDP-Glucuronosyltransferases for the Assessment of Human Drug Conjugation and Identification of Potential Drug Interactions Drug Metab. Dispos., January 1, 2001; 29(1): 48 - 53. [Abstract] [Full Text]

				P. Lautala, B. T. Ethell, J. Taskinen, and B. Burchell The Specificity of Glucuronidation of Entacapone and Tolcapone by Recombinant Human Udp-Glucuronosyltransferases Drug Metab. Dispos., November 1, 2000; 28(11): 1385 - 1389. [Abstract] [Full Text]

				S. Ammon, O. von Richter, U. Hofmann, K.-P. Thon, M. Eichelbaum, and G. Mikus In Vitro Interaction of Codeine and Diclofenac Drug Metab. Dispos., October 1, 2000; 28(10): 1149 - 1152. [Abstract] [Full Text] [PDF]

				C. King, B. Finley, and R. Franklin The Glucuronidation of Morphine by Dog Liver Microsomes: Identification of Morphine-6-O-Glucuronide Drug Metab. Dispos., June 1, 2000; 28(6): 661 - 663. [Abstract] [Full Text]

				M. B. Fisher, K. Campanale, B. L. Ackermann, M. VandenBranden, and S. A. Wrighton In Vitro Glucuronidation Using Human Liver Microsomes and The Pore-Forming Peptide Alamethicin Drug Metab. Dispos., May 1, 2000; 28(5): 560 - 566. [Abstract] [Full Text]

				Y. Ishii, A. J. Hansen, and P. I. Mackenzie Octamer Transcription Factor-1 Enhances Hepatic Nuclear Factor-1alpha -Mediated Activation of the Human UDP Glucuronosyltransferase 2B7 Promoter Mol. Pharmacol., May 1, 2000; 57(5): 940 - 947. [Abstract] [Full Text]

				V. M. Samokyszyn, W. E. Gall, G. Zawada, M. A. Freyaldenhoven, G. Chen, P. I. Mackenzie, T. R. Tephly, and A. Radominska-Pandya 4-Hydroxyretinoic Acid, a Novel Substrate for Human Liver Microsomal UDP-glucuronosyltransferase(s) and Recombinant UGT2B7 J. Biol. Chem., March 15, 2000; 275(10): 6908 - 6914. [Abstract] [Full Text] [PDF]

				S. A. Nowell, J. S. Massengill, S. Williams, A. Radominska-Pandya, T. R. Tephly, Z. Cheng, C. P. Strassburg, R. H. Tukey, S. L. MacLeod, N. P. Lang, et al. Glucuronidation of 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine by human microsomal UDP-glucuronosyltransferases: identification of specific UGT1A family isoforms involved Carcinogenesis, June 1, 1999; 20(6): 1107 - 1114. [Abstract] [Full Text] [PDF]

				B. L. Coffman, C. D. King, G. R. Rios, and T. R. Tephly The Glucuronidation of Opioids, Other Xenobiotics, and Androgens by Human UGT2B7Y(268) and UGT2B7H(268) Drug Metab. Dispos., January 1, 1998; 26(1): 73 - 77. [Abstract] [Full Text]

				M. D. Green, G. Bélanger, D. W. Hum, A. Bélanger, and T. R. Tephly Glucuronidation of Opioids, Carboxylic Acid-Containing Drugs, and Hydroxylated Xenobiotics Catalyzed by Expressed Monkey UDP-Glucuronosyltransferase 2B9 Protein Drug Metab. Dispos., December 1, 1997; 25(12): 1389 - 1394. [Abstract] [Full Text]

This Article Abstract Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Coffman, B. L. Articles by Tephly, T. R. Search for Related Content PubMed PubMed Citation Articles by Coffman, B. L. Articles by Tephly, T. R.