Drug Metabolism and Pharmacokinetics (DRUG METAB PHARMACOK)

Publications in this journal

• Article: Single Nucleotide Polymorphisms in SULT1A1 and SULT1A2 in a Korean population.

  Lee SJ, Kim WY, Jarrar YB, Kim YW, Lee SS, Shin JG, Yazun Bashir Jarrar
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  ABSTRACT: SULT1A1 and SULT1A2 are encoded on the same chromatid, and exhibit a 96% amino acid similarity. To screen for genetic variants in these two closely related genes, SULT1A1 and SULT1A2 were directly sequenced in 50 healthy Koreans. A total of 30 variations were identified in SULT1A1: eight in exons, thirteen in introns, and nine in the 5'-untranslated region. With regard to SULT1A2, 21 variants were identified, comprising seven in exons, five in introns, and nine in the 5'-untranslated region. Among these 51 variations, one in SULT1A1 and eight in SULT1A2 were previously unidentified, which include three coding variants (SULT1A2 R37Q, 110G>A; SULT1A2 G50S, 148G>A; SULT1A2 F286L, 3819C>A) and one null allele (SULT1A2 E217Stop, 3542G>T). Two LD blocks, major haplotype structures, and 7 haplotype-tagging SNPs were determined together for SULT1A1 and SULT1A2 as a single set. Frequencies of common functional variants were compared among ethnic groups. Since these two SULT enzymes are on the same chromatid in a parallel direction with overlapping substrate specificities, a combined analysis using LD and haplotype-tagging single-nucleotide polymorphisms (SNPs) will facilitate understanding of the variations in the sulfation reactions of a wide range of substrates, as compared with analysis of individual genes.
  Drug Metabolism and Pharmacokinetics 01/2013; 28(1).
• Article: Down-regulation of intestinal multidrug resistance-associated protein 2 in long-evans cinnamon rats.

  Makoto Chiba, Shirou Itagaki, Masaki Kobayashi, Takeshi Hirano, Ken Iseki
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  ABSTRACT: Wilson's disease is an inherited, autosomal recessive disorder of copper accumulation and toxicity. Lifelong chelation therapy is essential in all Wilson's disease patients. Intestinal absorption of some compounds is limited partly because they are preferentially transported in the secretory direction. Several ATP-binding cassette (ABC) transporters are expressed in the apical membrane of the small intestine and secrete various drugs into the lumen. In this study, we investigated the characteristics of the intestinal efflux ABC transporters in LEC rats. We found that the expression of multidrug resistance-associated protein 2 (Mrp2) in the jejunum of Long-Evans Cinnamon (LEC) rats, an animal model for Wilson's disease, is decreased.
  Drug Metabolism and Pharmacokinetics 01/2008; 22(6):450-5.
• Article: Call for papers to theme issue on membrane transporters: an opportunity to boost transporter studies.

  Hiroaki Yuasa
  Drug Metabolism and Pharmacokinetics 01/2008; 22(6):399-400.
• Article: Genetic variations of VDR/NR1I1 encoding vitamin D receptor in a Japanese population.

  Maho Ukaji, Yoshiro Saito, Hiromi Fukushima-Uesaka, Keiko Maekawa, Noriko Katori, Nahoko Kaniwa, Teruhiko Yoshida, Hiroshi Nokihara, Ikuo Sekine, Hideo Kunitoh, Yuichiro Ohe, Noboru Yamamoto, Tomohide Tamura, Nagahiro Saijo, Jun-ichi Sawada
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  ABSTRACT: The vitamin D receptor (VDR) is a transcriptional factor responsive to 1alpha,25-dihydroxyvitamin D(3) and lithocholic acid, and induces expression of drug metabolizing enzymes CYP3A4, CYP2B6 and CYP2C9. In this study, the promoter regions, 14 exons (including 6 exon 1's) and their flanking introns of VDR were comprehensively screened for genetic variations in 107 Japanese subjects. Sixty-one genetic variations including 25 novel ones were found: 9 in the 5'-flanking region, 2 in the 5'-untranslated region (UTR), 7 in the coding exons (5 synonymous and 2 nonsynonymous variations), 12 in the 3'-UTR, 19 in the introns between the exon 1's, and 12 in introns 2 to 8. Of these, one novel nonsynonymous variation, 154A>G (Met52Val), was detected with an allele frequency of 0.005. The single nucleotide polymorphisms (SNPs) that increase VDR expression or activity, -29649G>A, 2T>C and 1592((*)308)C>A tagging linked variations in the 3'-UTR, were detected at 0.430, 0.636, and 0.318 allele frequencies, respectively. Another SNP, -26930A>G, with reduced VDR transcription was found at a 0.028 frequency. These findings would be useful for association studies on VDR variations in Japanese.
  Drug Metabolism and Pharmacokinetics 01/2008; 22(6):462-7.
• Article: In vitro evaluation of photosensitivity risk related to genetic polymorphisms of human ABC transporter ABCG2 and inhibition by drugs.

  Ai Tamura, Yuko Onishi, Ran An, Shoko Koshiba, Kanako Wakabayashi, Kazuyuki Hoshijima, Waldemar Priebe, Takashi Yoshida, Satoshi Kometani, Takayoshi Matsubara, Kenta Mikuriya, Toshihisa Ishikawa
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  ABSTRACT: Since porphyrins are regarded as endogenous substrates for the ATP-binding cassette (ABC) transporter ABCG2, it is hypothesized that functional impairment owing to genetic polymorphisms or inhibition of ABCG2 by drugs may result in a disruption of cellular porphyrin homeostasis. In the present study, we expressed ABCG2 genetic variants, i.e., V12M, Q141K, S441N, and F489L, as well as the wild type (WT) in Flp-In-293 cells to examine the hypothesis. Cells expressing S441N and F489L variants exhibited high levels of both cellularly accumulated pheophorbide a and photosensitivity, when those cells were incubated with pheophorbide a and irradiated with visible light. To further elucidate the significance of ABCG2 in cellular porphyrin homeostasis, we observed cellular accumulation and compartmentation of porphyrin and pheophorbide a by means of a new fluorescence microscopy technology, and found that accumulation of porphyrin and pheophorbide a in the cytoplasm compartment was maintained at low levels in Flp-In-293 cells expressing ABCG2 WT, V12M, or Q141K. When ABCG2 was inhibited by imatinib or novobiocin, however, those cells became sensitive to light. Based on these results, it is strongly suggested that certain genetic polymorphisms and/or inhibition of ABCG2 by drugs can enhance the potential risk of photosensitivity.
  Drug Metabolism and Pharmacokinetics 01/2008; 22(6):428-40.
• Article: Decreased renal accumulation and toxicity of a new VCM formulation in rats with chronic renal failure.

  Naoko Hodoshima, Satohiro Masuda, Ken-Ichi Inui
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  ABSTRACT: We previously reported that MEEK, a generic product of vancomycin hydrochloride (VCM), was less nephrotoxic than a conventional preparation (S-VCM) in normal rats at a nephrotoxic dose (400 mg/kg) of VCM.(1)) To infer the clinical significance of this finding, we compared the risk of nephrotoxicity of these two formulations in rats with chronic renal failure in this study. MEEK or S-VCM was given intravenously to two weeks post-5/6 nephrectomy rats, and the pharmacokinetic profile of VCM and pathological evaluation were compared. There were no differences at the daily clinical dose (40 mg/kg), but at the twice the daily clinical dose (80 mg/kg), the mean plasma concentration of VCM was higher after S-VCM administration than after MEEK and the CL(tot) and CL(r) decreased to approximately 60% of those after MEEK. The renal tissue concentration of VCM was 1.5-fold higher at 24hr after S-VCM administration than after MEEK. Pathologically, no marked differences between the findings were observed at 24hr after administration of each formulation. These findings suggest that MEEK reduces renal damage caused by VCM and prevents the iatrogenic aggravation of nephrotoxicity. These results hold out hope that MEEK will permit high-dose administration of VCM, while revealing clinical significance of the nephrotoxicity-reduction by MEEK.
  Drug Metabolism and Pharmacokinetics 01/2008; 22(6):419-27.
• Article: Xenobiotic transporter-adaptor network.

  Yukio Kato
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  ABSTRACT: Many types of xenobiotic transporters have been identified. They generally exhibit multispecific recognition of various types of substrates, and mediate membrane permeation of therapeutic agents, thereby playing important roles in drug absorption and disposition. It has recently been proposed that protein-protein interactions involving the xenobiotic transporters may affect their function, localization and expression on plasma membranes. So-called adaptor proteins that directly interact with the transporters include PDZ domain-containing proteins (PSD95, Dlg and ZO1). These PDZ adaptors have multiple PDZ domains in their structure, and each PDZ domain can interact with the cytosolic region of the transporters, and so it has been hypothesized that transporters are localized within networks consisting of several transporters and adaptors. Interaction with a PDZ adaptor is essential for the cell-surface localization of at least some xenobiotic transporters, and therefore, such interaction could be required for efficiency and fidelity in the vectorial transport of xenobiotics and therapeutic agents in epithelial cells. This review article summarizes recent evidence on the interactions of xenobiotic transporters with adaptor proteins, and presents a working hypothesis concerning their pharmacological significance.
  Drug Metabolism and Pharmacokinetics 01/2008; 22(6):401-8.
• Article: Distinct effects of omeprazole and rabeprazole on the tacrolimus blood concentration in a kidney transplant recipient.

  Kazushige Takahashi, Ikuko Yano, Yuga Fukuhara, Toshiya Katsura, Takeshi Takahashi, Noriyuki Ito, Shingo Yamamoto, Osamu Ogawa, Ken-ichi Inui
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  ABSTRACT: Proton-pump inhibitors (PPIs, e.g. omeprazole and rabeprazole) are often administered to transplant patients as a treatment or prophylaxis for ulcers after surgery. Since tacrolimus and PPIs share the CYP3A4 system for metabolism, pharmacokinetic interactions are anticipated when they are administered simultaneously. We present a Japanese male patient who underwent a living-donor kidney transplantation having received tacrolimus, mycophenolate mofetil, and prednisolone for immunosuppression. The concentration/dose (C/D) ratio for tacrolimus was markedly higher during the period of treatment with omeprazole than ranitidine or rabeprazole. The results of liver functional tests were within the normal range during the use of these three antacid drugs. Since the higher C/D ratio for tacrolimus when omeprazole was being administered did not result from a decrease in the elimination of tacrolimus due to hepatic dysfunction, drug interaction between omeprazole and tacrolimus was strongly suspected. The present case indicates that rabeprazole can be used safely in place of omeprazole in kidney transplant recipients receiving tacrolimus.
  Drug Metabolism and Pharmacokinetics 01/2008; 22(6):441-4.
• Article: Capsaicin-induced increase of intestinal cefazolin absorption in rats.

  Yukiko Komori, Tetsuya Aiba, Chie Nakai, Risa Sugiyama, Hiromu Kawasaki, Yuji Kurosaki
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  ABSTRACT: The effect of capsaicin on intestinal cefazolin absorption was examined by means of an in situ closed loop method in rats to clarify whether the vanilloid receptor (TRPV1) is involved in drug absorption driven by passive diffusion. In control experiments with 1 mg/mL cefazolin, the amount of cefazolin absorbed from the closed loop was 15.3+/-1.5 microg/cm in the rat jejunum. The absorption amount was increased to 22.8+/-0.9 and 23.4+/-2.4 microg/cm when capsaicin was applied with cefazolin at concentrations of 10 and 400 microM, respectively. The enhancing effect of capsaicin on cefazolin absorption was suppressed when ruthenium red, a non-selective inhibitor of transient receptor potential (TRP) cation channels, was intravenously infused into the rat during the experiment. Cefazolin accumulation in the intestinal tissue was not altered in the presence of capsaicin. Collectively, the mechanism accounting for the capsaicin-induced increase in the intestinal cefazolin absorption is probably that capsaicin associating with TRPV1 increases the intrinsic permeability of cefazolin in intestine.
  Drug Metabolism and Pharmacokinetics 01/2008; 22(6):445-9.
• Article: Prediction of the metabolic interaction of nateglinide with other drugs based on in vitro studies.

  Toshiyuki Takanohashi, Tomonori Koizumi, Ryuichi Mihara, Kazuho Okudaira
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  ABSTRACT: Nateglinide is an antidiabetic agent metabolized by CYP2C9 and CYP3A4; hence inhibitors of these CYP isozymes may interact with nateglinide. There are, however, only limited in vitro data on how to predict drug-drug interactions in vivo. We examined the effects of 18 drugs that may be prescribed together with nateglinide (metformin, buformin, aspirin, gemfibrozil, simvastatin, pioglitazone, rosiglitazone, carbamazepine, clarithromycin, gliclazide, clofibrate, fluconazole, bezafibrate, phenylbutazone, nifedipine, famotidine, ibuprofen and miconazole) on the conversion of nateglinide to its major metabolite (N-[trans-4-(1-hydroxy-1-methylethyl)-cyclohexanecarbonyl]-D-phenylalanine) using human liver microsomes. Eight compounds showed a<50% inhibitory effect and we estimated the K(i) values for the remaining 10 compounds. Except for fluconazole and miconazole, 1+I(in, max, u)/K(i) calculated from the K(i) values, was approximately 1 and thus the possibility of a drug-drug interaction was considered low. The value for fluconazole suggested the risk of interaction and agreed with the results of clinical studies in which the AUC of nateglinide increased by 48% when it was co-administered with fluconazole. The present study showed that nateglinide metabolism would hardly be affected by the drugs used in this study, except for miconazole and fluconazole that are potent inhibitors of multiple isoforms of CYPs.
  Drug Metabolism and Pharmacokinetics 01/2008; 22(6):409-18.
• Article: Genetic variations and frequencies of major haplotypes in SLCO1B1 encoding the transporter OATP1B1 in Japanese subjects: SLCO1B1*17 is more prevalent than *15.

  Su-Ryang Kim, Yoshiro Saito, Kimie Sai, Kouichi Kurose, Keiko Maekawa, Nahoko Kaniwa, Shogo Ozawa, Naoyuki Kamatani, Kuniaki Shirao, Noboru Yamamoto, Tetsuya Hamaguchi, Hideo Kunitoh, Yuichiro Ohe, Yasuhide Yamada, Tomohide Tamura, Teruhiko Yoshida, Hironobu Minami, Atsushi Ohtsu, Nagahiro Saijo, Jun-ichi Sawada
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  ABSTRACT: A liver-specific transporter organic anion transporting polypeptide 1B1 (OATP1B1, also known as OATP-C) is encoded by SLCO1B1 and mediates uptake of various endogenous and exogenous compounds from blood into hepatocytes. In this study, 15 SLCO1B1 exons (including non-coding exon 1) and their flanking introns were comprehensively screened for genetic variations in 177 Japanese subjects. Sixty-two genetic variations, including 28 novel ones, were found: 7 in the 5'-flanking region, 1 in the 5'-untranslated region (UTR), 13 in the coding exons (9 nonsynonymous and 4 synonymous variations), 5 in the 3'-UTR, and 36 in the introns. Five novel nonsynonymous variations, 311T>A (Met104Lys), 509T>C (Met170Thr), 601A>G (Lys201Glu), 1553C>T (Ser518Leu), and 1738C>T (Arg580Stop), were found as heterozygotes. The allele frequencies were 0.008 for 1738C>T (Arg580Stop) and 0.003 for the four other variations. Arg580Stop having a stop codon at codon 580 results in loss of half of transmembrane domain (TMD) 11, TMD12, and a cytoplasmic tail, which might affect transport activity. In addition, novel variations, IVS12-1G>T at the splice acceptor site and -3A>C in the Kozak motif, were detected at 0.003 and 0.014 frequencies, respectively. Haplotype analysis using -11187G>A, -3A>C, IVS12-1G>T and 9 nonsynonymous variations revealed that the haplotype frequencies for (*)1b, (*)5, (*)15, and (*)17 were 0.469, 0.000 (not detected), 0.037, and 0.133, respectively. These data would provide fundamental and useful information for pharmacogenetic studies on OATP1B1-transported drugs in Japanese.
  Drug Metabolism and Pharmacokinetics 01/2008; 22(6):456-61.
• Article: In vitro metabolism of CP-122,721 ((2S,3S)-2-phenyl-3-[(5-trifluoromethoxy-2-methoxy)benzylamino]piperidine), a non-peptide antagonist of the substance P receptor.

  R Scott Obach, Jeannine M Margolis, Michael J Logman
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  ABSTRACT: The metabolism of CP-122,721, a neurokinin-1 antagonist, has been examined in vitro using hepatic microsomes from human and animal species, and recombinant heterologously expressed P450 enzymes. Metabolism occurs primarily via O-demethylation and N-dealkylation reactions. In human liver microsomes, O-demethylation was shown to be catalyzed by CYP2D6 with a low K(M) value. N-dealkyation was shown to be catalyzed primarily by CYP3A4. When scaled to in vivo, in vitro intrinsic clearance data yielded a reasonable correlation across species. CP-122,721 was shown to be metabolized by parallel pathways to 5-trifluoromethoxysalicylic acid, which had been observed as a major circulating metabolite in humans after oral administration of CP-122,721. The involvement of CYP1A2, CYP3A4, and MAO-B was demonstrated in the pathways leading to 5-trifluoromethoxysalicylic acid. The O-desmethyl metabolite of CP-122,721 was shown to undergo a P450 catalyzed O-detrifluoromethylation reaction yielding a p-hydroquinone metabolite. The reaction was shown to be catalyzed by CYP3A4. Incubation under (18)O(2) yielded the hydroquinone containing O-18, consistent with this reaction occurring via an ispo substitution mechanism. Combined, these findings provide a comprehensive understanding of the metabolism of this new agent.
  Drug Metabolism and Pharmacokinetics 11/2007; 22(5):336-49.
• Article: Microdosing for reduction of the time and resources for drug development.

  Kenichi Sudo
  Drug Metabolism and Pharmacokinetics 11/2007; 22(5):327.
• Article: UGT2B7*3 did not affect the pharmacokinetics of R- and S-carvedilol in healthy Japanese.

  Mutsuko Honda, Wakako Toyoda, Takako Shimizu, Isao Horiuchi, Yuichiro Kayano, Masato Taguchi, Takashi Nozawa, Hiroshi Inoue, Yukiya Hashimoto
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  ABSTRACT: We previously investigated the pharmacokinetics of R- and S-carvedilol in 54 healthy Japanese subjects, and reported that the oral clearance (CL/F) and apparent volume of distribution (V/F) of both enantiomers in subjects with the CYP2D6*10 allele were significantly lower than those in subjects without the CYP2D6*10 allele. In the present study, we examined the genotype of UGT2B7 in these 54 subjects, and investigated the effect of UGT2B7*3 on the pharmacokinetics of R- and S-carvedilol. Forty-three subjects did not have the UGT2B7*3 allele, and 11 subjects had one UGT2B7*3 allele. CL/F and V/F values of R- and S-carvedilol in the subjects with one UGT2B7*3 allele were similar to those without the UGT2B7*3 allele, indicating that the UGT2B7*3 allele did not significantly affect the systemic clearance (CL) and bioavailability (F) of the two enantiomers.
  Drug Metabolism and Pharmacokinetics 11/2007; 22(5):382-6.
• Article: Rapid and drastic induction of CYP3A4 mRNA expression via vitamin D receptor in human intestinal LS180 cells.

  Shiro Fukumori, Toshiya Murata, Masato Taguchi, Yukiya Hashimoto
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  ABSTRACT: The aim of this study was to evaluate the usefulness of human intestinal LS180 cells for studying the induction of CYP3A4 mRNA expression via vitamin D receptor (VDR). CYP3A4 mRNA expression in LS180 cells treated with 100 nM 1alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)) for 6 and 24 h was approximately 80- and 500-fold higher than the control, respectively. A protein kinase (PK) inhibitor (staurosporine), c-jun N-terminal kinase (JNK) pathway inhibitor (curcumin), and JNK inhibitor (SP600125) attenuated 1alpha,25(OH)(2)D(3)-induced CYP3A4 mRNA expression, suggesting that the PK-JNK pathway contributed to the rapid and drastic induction of CYP3A4 expression via VDR in LS180 cells. The ability of CYP3A4 mRNA induction in LS180 cells was highly dependent on the site and number of vitamin D(3) and D(2) hydroxylation. In addition, short-time (6 h) treatment of LS180 cells with cytotoxic secondary bile acids, lithocholic acid (LCA) and 3-keto-LCA also significantly induced the mRNA expression of CYP3A4. LS180 cells may be useful to quickly investigate the CYP3A4-inducing effect of drugs, xenobiotics, and/or endogenous substrates in the intestinal epithelia.
  Drug Metabolism and Pharmacokinetics 11/2007; 22(5):377-81.
• Article: Characterization of hepatobiliary organic anion transporters in Long-Evans Cinnamon rats.

  Makoto Chiba, Shirou Itagaki, Masaki Kobayashi, Takeshi Hirano, Ken Iseki
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  ABSTRACT: The liver plays important roles in the detoxification of xenobiotics. Hepatobiliary transporters contribute to hepatic uptake and efflux processes of xenobiotecs. Expressions of these transporters may be modulated under the condition of hepatic failure. Long-Evans Cinnamon (LEC) rats provide a pertinent model for basic and clinical studies on hepatitis. However, only a few reports describing the properties of hepatobiliary transporters in LEC rats have appeared in the literature. We investigated the expression levels of hepatobiliary transporters in LEC rats by real-time RT-PCR. We found that hepatic expressions of three sinusoidal organic anion transporters, Ntcp, Oatp1a1 and Oatp1a4, were decreased in LEC rats. However, no significant difference of the expressions of Mrp2 and Bsep, organic anion transporters located on canalicular membrane, were found between Wistar rats and LEC rats.
  Drug Metabolism and Pharmacokinetics 11/2007; 22(5):387-90.
• Article: Pharmacokinetics of aripiprazole, a new antipsychotic, following oral dosing in healthy adult Japanese volunteers: influence of CYP2D6 polymorphism.

  Masanori Kubo, Toshiko Koue, Hiromi Maune, Tsuyoshi Fukuda, Junichi Azuma
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  ABSTRACT: We investigated the pharmacokinetics (PK) of aripiprazole, a newly developed antipsychotic, and its active metabolite in healthy Japanese, and the influence of CYP2D6 polymorphism on the PK of aripiprazole. Following a single oral 6 mg dose, the mean C(max), t(max), and t(1/2, z) (terminal phase half life) of aripiprazole were 31.0 ng/mL, 3.6 hr, and 61.0 hr, respectively. The t(1/2, z) in CYP2D6 IM subjects (75.2 hr) was significantly (p<0.01) longer than that in CYP2D6 EM subjects (45.8 hr), and the systemic clearance of IM subjects was approximately 60% that of EM subjects. The PK in one subject with the CYP2D6*41 homozygote was similar to that of IM subjects. In repeated oral administration, plasma concentrations of aripiprazole and active metabolite both reached a steady state by Day 14. The half-life of aripiprazole following repeated administration was similar to that following single administration, suggesting that pharmacokinetics was constant during 14-day administration. Our investigations revealed that there is no clear ethnic difference between Japanese and Western subjects in terms of mean plasma PK, while the CYP2D6*10 allele distinctive to Asian populations influences the PK of aripiprazole. Moreover, our observations suggest that the CYP2D6*41 allele significantly affects drug-metabolizing activity.
  Drug Metabolism and Pharmacokinetics 11/2007; 22(5):358-66.
• Article: Transporter-mediated hepatic uptake of ulifloxacin, an active metabolite of a prodrug-type new quinolone antibiotic prulifloxacin, in rats.

  Yukihiro Yagi, Makoto Aoki, Maki Iguchi, Shigeki Shibasaki, Tohru Kurosawa, Yukio Kato, Akira Tsuji
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  ABSTRACT: Prulifloxacin (PUFX) is a prodrug-type new quinolone antibiotic and immediately converted to an active metabolite, ulifloxacin (UFX). It has been previously reported that UFX is highly excreted into the bile, although the hepatic uptake process of UFX has not been investigated yet. In this study, we attempted to characterize the mechanism of hepatic uptake of UFX in rats. The hepatic uptake in vivo was evaluated by integration plot analysis. Furthermore, the uptake of [(14)C]-UFX by isolated rat hepatocytes was measured, and the effects of several transporter inhibitors and other quinolone antibiotics on the uptake were examined. The hepatic uptake clearance of UFX (1 mg/kg) was calculated to be 37.7 mL/min/kg, which was larger than those at doses of 5 and 25 mg/kg and was decreased by co-administration of cyclosporine A (CysA; 30 mg/kg). The uptake of [(14)C]-UFX by isolated rat hepatocytes linearly increased up to 1 min and also inhibited by CysA. Other quinolone antibiotics inhibited the [(14)C]-UFX uptake in a concentration-dependent manner, whereas taurocholate and estrone-3-sulfate partially inhibited the [(14)C]-UFX uptake. These results demonstrate that a carrier-mediated transport system which is common to the quinolone antibiotics is involved in the uptake of UFX in the rat liver.
  Drug Metabolism and Pharmacokinetics 11/2007; 22(5):350-7.
• Article: Hepatocyte nuclear factor 1 alpha and 4 alpha are factors involved in interindividual variability in the expression of UGT1A6 and UGT1A9 but not UGT1A1, UGT1A3 and UGT1A4 mRNA in human livers.

  Sasitorn Aueviriyavit, Tomomi Furihata, Kaori Morimoto, Kaoru Kobayashi, Kan Chiba
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  ABSTRACT: UDP-glucuronosyltransferases (UGTs) catalyze phase-II biotransformation reaction of a variety of substances. Among the UGT1A isoforms, UGT1A1, UGT1A3, UGT1A4, UGT1A6 and UGT1A9 are predominantly expressed in the liver. Interindividual variability in expression of these isoforms would cause interindividual differences in drug response, toxicity and cancer susceptibility. In the present study, we investigated the interindividual variability in UGT1A mRNA expression and whether hepatocyte nuclear factor 1alpha (HNF1alpha) and HNF4alpha were factors responsible for their variability in human livers. The amounts of UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9, HNF1alpha and HNF4alpha mRNA in 18 human livers were measured by quantitative real-time polymerase chain reaction. The largest and smallest interindividual differences in expression levels were observed in UGT1A1 (8.6-fold) and UGT1A4 (2.5-fold) mRNA, respectively. The amounts of HNF1alpha and HNF4alpha mRNA were strongly correlated with the amount of UGT1A9 mRNA and moderately correlated with that of UGT1A6 mRNA, whereas no significant correlation was found with the amounts of UGT1A1, UGT1A3 and UGT1A4 mRNA. Our results suggest that HNF1alpha and HNF4alpha are the factors involved in the interindividual variability of UGT1A6 and UGT1A9 mRNA expression. Further studies of other transcription factors are needed to clarify the factor(s) determining the interindividual variations in UGT1A1, UGT1A3 and UGT1A4 mRNA expression.
  Drug Metabolism and Pharmacokinetics 11/2007; 22(5):391-8.
• Article: Metabolism of tacrolimus (FK506) and recent topics in clinical pharmacokinetics.

  Kazuhide Iwasaki
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  ABSTRACT: Tacrolimus (FK506), an immunosuppressive drug, is co-medicated with multiple drugs under clinical conditions. Tacrolimus is highly lipophilic and is excreted from the body after receiving extensive metabolism. Due to its narrow therapeutic window following organ transplantation, tacrolimus requires therapeutic drug monitoring by an enzyme immunoassay using the monoclonal antibody raised against tacrolimus. Therefore, metabolism studies including drug-drug interaction and metabolite identification studies are essential for the efficient development and clinically optimal usage of this drug. Tacrolimus was metabolized by the cytochrome P450 (CYP) 3A subfamily. Metabolic drug-drug interaction studies were conducted to provide information regarding the optimal usage of tacrolimus, and its metabolism was inhibited by known CYP3A inhibitors such as ketoconazole, cyclosporine A, and nifedipine. Recent reports on clinical pharmacokinetics indicate that dose levels of tacrolimus need to be adjusted in transplant patients with CYP3A5 polymorphism.
  Drug Metabolism and Pharmacokinetics 11/2007; 22(5):328-35.