Biomedical subjects

Toshiya Katsura

Publications and source records attributed to Toshiya Katsura.

At least 19 recordsLinked to original sources

PubMed2006

Is MIBG a substrate of P-glycoprotein?

PURPOSE: Radionuclide therapy with 131I-labelled meta-iodobenzylguanidine ([131I]MIBG) is effective in cases where it is difficult to carry out surgical resection or debulking of neuroendocrine tumours (NETs). However, it has recently been reported that P-glycoprotein (P-gp) is expressed in these NETs. Therefore, it is important to clarify whether MIBG is a substrate of P-gp or not. In this study, using a human cell line which overexpresses P-gp, LLC-GA5-COL150, we investigated this question. METHODS: The transcellular transport and accumulation of [125I]MIBG were measured using monolayer cultures grown in Transwell chambers. [125I]MIBG was added to either the basolateral or the apical side, aliquots of the incubation medium on the other side were taken at specified times, and the radioactivity was measured. For accumulation experiments, the cells on the filters were solubilised and the radioactivity in aliquots was measured. RESULTS: There were no significant differences in the transport of MIBG between LLC-PK1 and LLC-GA5-COL150 monolayers in either direction until 60 min. With respect to the accumulation of MIBG, there were no significant differences between LLC-PK1 and LLC-GA5-COL150 cells in either direction. CONCLUSION: MIBG is not a substrate of P-gp. Therefore, radionuclide therapy with MIBG would be useful in the treatment of NETs expressing P-gp.

3-Iodobenzylguanidine↗

PubMed2006

Oppositely directed H+ gradient functions as a driving force of rat H+/organic cation antiporter MATE1.

Recently, we have isolated the rat (r) H(+)/organic cation antiporter multidrug and toxin extrusion 1 (MATE1) and reported its tissue distribution and transport characteristics. Functional characterization suggested that an oppositely directed H(+) gradient serves as a driving force for the transport of a prototypical organic cation, tetraethylammonium, by MATE1, but there is no direct evidence to prove this. In the present study, therefore, we elucidated the driving force of tetraethylammonium transport via rMATE1 using plasma membrane vesicles isolated from HEK293 cells stably expressing rMATE1 (HEK-rMATE1 cells). A 70-kDa rMATE1 protein was confirmed to exist in HEK-rMATE1 cells, and the transport of various organic cations including [(14)C]tetraethylammonium was stimulated in intracellular acidified HEK-rMATE1 cells but not mock cells. The transport of [(14)C]tetraethylammonium in membrane vesicles from HEK-rMATE1 cells exhibited the overshoot phenomenon only when there was an outwardly directed H(+) gradient, as observed in rat renal brush-border membrane vesicles. The overshoot phenomenon was not observed in the vesicles from mock cells. The stimulated [(14)C]tetraethylammonium uptake by an H(+) gradient [intravesicular H(+) concentration ([H(+)](in)) > extravesicular H(+) concentration ([H(+)](out))] was significantly reduced in the presence of a protonophore, carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP). [(14)C]tetraethylammonium uptake was not changed in the presence of valinomycin-induced membrane potential. These findings definitively indicate that an oppositely directed H(+) gradient serves as a driving force of tetraethylammonium transport via rMATE1, and this is the first demonstration to identify the driving force of the MATE family. The present experimental strategy is very useful in identifying the driving force of cloned transporters whose driving force has not been evaluated.

Animals↗

PubMed2006

Cisplatin and oxaliplatin, but not carboplatin and nedaplatin, are substrates for human organic cation transporters (SLC22A1-3 and multidrug and toxin extrusion family).

We have examined the role of the human organic cation transporters [hOCTs and human novel organic cation transporter (hOCTN); SLC22A1-5] and apical multidrug and toxin extrusion (hMATE) in the cellular accumulation and cytotoxicity of platinum agents using the human embryonic kidney (HEK) 293 cells transiently transfected with the transporter cDNAs. Both the cytotoxicity and accumulation of cisplatin were enhanced by the expression of hOCT2 and weakly by hOCT1, and those of oxaliplatin were also enhanced by the expression of hOCT2 and weakly by hOCT3. The hOCT-mediated uptake of tetraethylammonium (TEA) was markedly decreased in the presence of cisplatin in a concentration-dependent manner. However, oxaliplatin showed almost no influence on the TEA uptakes in the HEK293 cells expressing hOCT1, hOCT2, and hOCT3. The hMATE1 and hMATE2-K, but not hOCTN1 and OCTN2, mediated the cellular accumulation of cisplatin and oxaliplatin without a marked release of lactate dehydrogenase. Oxaliplatin, but not cisplatin, markedly decreased the hMATE2-K-mediated TEA uptake. However, the inhibitory effect of cisplatin and oxaliplatin against the hMATE1-mediated TEA uptake was similar. The release of lactate dehydrogenase and the cellular accumulation of carboplatin and nedaplatin were not found in the HEK293 cells transiently expressing these seven organic cation transporters. These results indicate that cisplatin is a relatively good substrate of hOCT1, hOCT2, and hMATE1, and oxaliplatin is of hOCT2, hOCT3, hMATE1, and hMATE2-K. These transporters could play predominant roles in the tissue distribution and anticancer effects and/or adverse effects of platinum agent-based chemotherapy.

Biological Transport↗

PubMed2006

Human organic anion transporter 3 gene is regulated constitutively and inducibly via a cAMP-response element.

Human organic anion transporter (OAT) 3 (SLC22A8) is localized to the basolateral membranes of renal tubular epithelial cells and plays a critical role in the excretion of anionic compounds. We previously reported that interindividual variation in the OAT3 mRNA level corresponded to interindividual differences in the rate of renal excretion of cefazolin. However, there is little information available on the molecular mechanisms regulating the gene expression of OAT3. Therefore, in the present study, we examined the transcriptional regulation of human OAT3. A deletion analysis of the OAT3 promoter suggested that the region spanning -214 to -77 base pairs was essential for basal transcriptional activity. This region contained a perfectly conserved cAMP-response element (CRE), and a mutation here led to a reduction in promoter activity. Electrophoretic mobility shift assays showed that CRE-binding protein (CREB)-1 and activating transcription factor (ATF)-1 bound to CRE. The activity of the OAT3 promoter was increased through the phosphorylation of CREB-1 and ATF-1 by treatment with 8-bromo-cAMP. This paper reports the first characterization of the human OAT3 promoter and shows that CREB-1 and ATF-1 function as constitutive and inducible transcriptional regulators of the human OAT3 gene via CRE.

Base Sequence↗

PubMed2006

Identification and functional characterization of a new human kidney-specific H+/organic cation antiporter, kidney-specific multidrug and toxin extrusion 2.

A cDNA coding a new H+/organic cation antiporter, human kidney-specific multidrug and toxin extrusion 2 (hMATE2-K), has been isolated from the human kidney. The hMATE2-K cDNA had an open reading frame that encodes a 566-amino acid protein, which shows 94, 82, 52, and 52% identity with the hMATE2, hMATE2-B, hMATE1, and rat MATE1, respectively. Reverse transcriptase-PCR revealed that hMATE2-K mRNA but not hMATE2 was expressed predominantly in the kidney, and hMATE2-B was ubiquitously found in all tissues examined except the kidney. The immunohistochemical analyses revealed that the hMATE2-K as well as the hMATE1 was localized at the brush border membranes of the proximal tubules. HEK293 cells that were transiently transfected with the hMATE2-K cDNA but not hMATE2-B exhibited the H+ gradient-dependent antiport of tetraethylammonium (TEA). Transfection of hMATE2-B had no affect on the hMATE2-K-mediated transport of TEA. hMATE2-K also transported cimetidine, 1-methyl-4-phenylpyridinium (MPP), procainamide, metformin, and N1-methylnicotinamide. Kinetic analyses demonstrated that the Michaelis-Menten constants for the hMATE2-K-mediated transport of TEA, MPP, cimetidine, metformin, and procainamide were 0.83 mM, 93.5 microM, 0.37 mM, 1.05 mM, and 4.10 mM, respectively. Ammonium chloride-induced intracellular acidification significantly stimulated the hMATE2-K-dependent transport of organic cations such as TEA, MPP, procainamide, metformin, N1-methylnicotinamide, creatinine, guanidine, quinidine, quinine, thiamine, and verapamil. These results indicate that hMATE2-K is a new human kidney-specific H+/organic cation antiporter that is responsible for the tubular secretion of cationic drugs across the brush border membranes.

Alternative Splicing↗

PubMed2006

Induction of intestinal peptide transporter 1 expression during fasting is mediated via peroxisome proliferator-activated receptor alpha.

We previously demonstrated that starvation markedly increased the amount of mRNA and protein levels of the intestinal H+/peptide cotransporter (PEPT1) in rats, leading to altered pharmacokinetics of the PEPT1 substrates. In the present study, the mechanism underlying this augmentation was investigated. We focused on peroxisome proliferator-activated receptor alpha (PPARalpha), which plays a pivotal role in the adaptive response to fasting in the liver and other tissues. In 48-h fasted rats, the expression level of PPARalpha mRNA in the small intestine markedly increased, accompanied by the elevation of serum free fatty acids, which are endogenous PPARalpha ligands. Oral administration of the synthetic PPARalpha ligand WY-14643 to fed rats increased the mRNA level of intestinal PEPT1. Furthermore, treatment of the human intestinal model, Caco-2 cells, with WY-14643 resulted in enhanced PEPT1 mRNA expression and uptake activity of glycylsarcosine. In the small intestine of PPARalpha-null mice, augmentation of PEPT1 mRNA during fasting was completely abolished. In the kidney, fasting did not induce PEPT1 expression in either PPARalpha-null or wild-type mice. Together, these results indicate that PPARalpha plays critical roles in fasting-induced intestinal PEPT1 expression. In addition to the well-established roles of PPARalpha, we propose a novel function of PPARalpha in the small intestine, that is, the regulation of nitrogen absorption through PEPT1 during fasting.

Acyl-CoA Oxidase↗

PubMed2006

The transcription factor Cdx2 regulates the intestine-specific expression of human peptide transporter 1 through functional interaction with Sp1.

H(+)/peptide cotransporter 1 (PEPT1, SLC15A1) localized at the brush-border membranes of intestinal epithelial cells plays important roles in the intestinal absorption of small peptides and a variety of peptidemimetic drugs. We previously demonstrated that transcription factor Sp1 functions as a basal transcriptional regulator of human PEPT1. However, the factor responsible for the intestine-specific expression of PEPT1 remains unknown. In the present study, we investigated the effect of the intestinal transcription factors on the transcription of the PEPT1 gene and found that only Cdx2 markedly trans-activated the PEPT1 promoter. However, the promoter region responsible for this effect lacked a typical Cdx2-binding sequence, but instead, possessed some Sp1-binding sites. In vitro experiments using Caco-2 cells showed that (1) mutation of the Sp1-binding site diminished the effect of Cdx2, (2) co-expression of Cdx2 and Sp1 synergistically trans-activated the PEPT1 promoter and (3) Sp1 protein was immunoprecipitated with Cdx2 protein. These results raise the possibility that Cdx2 modulates the PEPT1 promoter by interaction with Sp1. The significance of Cdx2 in vivo for PEPT1 regulation was shown by the determination of mRNA levels of Cdx2 and PEPT1 in human tissue. In gastric samples, some with intestinal metaplasia, the levels of PEPT1 and Cdx2 mRNA were highly correlated. Taken together, the present study suggests that Cdx2 plays a key role in the transcriptional regulation of the intestine-specific expression of PEPT1, possibly through interaction with Sp1.

Binding Sites↗

PubMed2006

Transport characteristics of a novel peptide transporter 1 substrate, antihypotensive drug midodrine, and its amino acid derivatives.

Midodrine is an oral drug for orthostatic hypotension. This drug is almost completely absorbed after oral administration and converted into its active form, 1-(2',5'-dimethoxyphenyl)-2-aminoethanol) (DMAE), by the cleavage of a glycine residue. The intestinal H+-coupled peptide transporter 1 (PEPT1) transports various peptide-like drugs and has been used as a target molecule for improving the intestinal absorption of poorly absorbed drugs through amino acid modifications. Because midodrine meets these requirements, we examined whether midodrine can be a substrate for PEPT1. The uptake of midodrine, but not DMAE, was markedly increased in PEPT1-expressing oocytes compared with water-injected oocytes. Midodrine uptake by Caco-2 cells was saturable and was inhibited by various PEPT1 substrates. Midodrine absorption from the rat intestine was very rapid and was significantly inhibited by the high-affinity PEPT1 substrate cyclacillin, assessed by the alteration of the area under the blood concentration-time curve for 30 min and the maximal concentration. Some amino acid derivatives of DMAE were transported by PEPT1, and their transport was dependent on the amino acids modified. In contrast to neutral substrates, cationic midodrine was taken up extensively at alkaline pH, and this pH profile was reproduced by a 14-state model of PEPT1, which we recently reported. These findings indicate that PEPT1 can transport midodrine and contributes to the high bioavailability of this drug and that Gly modification of DMAE is desirable for a prodrug of DMAE.

Amino Acids↗

PubMed2006

Androgen receptor is responsible for rat organic cation transporter 2 gene regulation but not for rOCT1 and rOCT3.

PURPOSE: Organic cation transporters 1-3 (OCT1-3; Slc22a1-3) mediate the membrane transport of organic cations in the kidney. We previously reported that rat (r)OCT2 expression in the kidney was regulated by testosterone. In this study, we examined the transcriptional mechanisms underlying the testosterone-dependent regulation of rOCT2 expression. METHODS: Approximately 3000-bp fragments of the rOCT1-3 promoter region were isolated, and promoter activities were measured in the renal epithelial cell line LLC-PK1 with the coexpression of rat androgen receptor. RESULTS: Among reporter constructs tested, only rOCT2 promoter activity was stimulated by testosterone. This stimulation was suppressed by nilutamide, an antiandrogen drug. Reporter assays using deletion constructs and mutational constructs of putative androgen response elements (ARE) in the rOCT2 promoter region suggested that two AREs, located at approximately -3000 and -1300, respectively, play an important role in the induction by testosterone. CONCLUSIONS: Testosterone induces the expression of rOCT2, but not of rOCT1 and rOCT3, via the AR-mediated transcriptional pathway. This is the first study to address the transcriptional mechanisms of testosterone-dependent gene regulation of the Slc22 family.

Androgens↗

PubMed2006

Cyclosporine exposure and calcineurin phosphatase activity in living-donor liver transplant patients: twice daily vs. once daily dosing.

We have compared the pharmacokinetics and pharmacodynamics of cyclosporine between once- and twice-daily dosing regimens in de novo patients of living-donor liver transplantation (LDLT). A total of 14 patients were enrolled in this study, who had received cyclosporine microemulsion (Neoral) twice a day (BID, n = 5) or once daily in the morning (QD, n = 9) after transplantation. On postoperative day (POD) 6, the QD regimen significantly increased cyclosporine exposure; the blood concentration at 2 hours postdose (C2) and area under the concentration-time curve (AUC) for 4 hours (AUC(0-4)), compared with the BID regimen. Moreover, the area under the calcineurin (CaN) activity in peripheral blood mononuclear cells time-curve (AUA) for 12 hours (AUA(0-12)) and 24 hours (AUA(0-24)) were decreased by approximately 42 and 25% with the QD regimen relative to the BID regimen, respectively. The C2 level was significantly correlated with the AUC(0-4) (r2 = 0.95), which was negatively related to the AUA(0-12) with a large interindividual variability (r(2) = 0.59). However, a significant correlation was found between the AUA(0-12) or AUA(0-24) and CaN activity at trough time points. According to a maximum inhibitory effect attributable to the drug (E(max)) model, the mean estimates of E(max) and the C(b) value that gives a half-maximal effect (EC50) for CaN inhibition were not significantly different between the 2 groups, respectively. These findings suggest that a once daily morning administration of cyclosporine may improve oral absorption and help to provide an effective CaN inhibition early after LDLT. Furthermore, CaN activity at trough time points would be a single surrogate predictor for the overall CaN activity throughout dosing intervals following cyclosporine administration.

Adult↗

PubMed2006

Molecular cloning, functional characterization and tissue distribution of rat H+/organic cation antiporter MATE1.

PURPOSE: Transport characteristics and tissue distribution of the rat H+/organic cation antiporter MATE1 (multidrug and toxin extrusion 1) were examined. METHODS: Rat MATE1 cDNA was isolated by polymerase chain reaction (PCR) cloning. Transport characteristics of rat MATE1 were assessed by HEK293 cells transiently expressing rat MATE1. The mRNA expression of rat MATE1 was examined by Northern blot and real-time PCR analyses. RESULTS: The uptake of a prototypical organic cation tetraethylammonium (TEA) by MATEI-expressing cells was concentration-dependent, and showed the greatest value at pH 8.4 and the lowest at pH 6.0-6.5. Intracellular acidification induced by ammonium chloride resulted in a marked stimulation of TEA uptake. MATE1 transported not only organic cations such as cimetidine and metformin but also the zwitterionic compound cephalexin. MATE1 mRNA was expressed abundantly in the kidney and placenta, slightly in the spleen, but not expressed in the liver. Real-time PCR analysis of microdissected nephron segments showed that MATE1 was primarily expressed in the proximal convoluted and straight tubules. CONCLUSIONS: These findings indicate that MATE1 is expressed in the renal proximal tubules and can mediate the transport of various organic cations and cephalexin using an oppositely directed H+ gradient.

Animals↗

PubMed2006

Population pharmacokinetic and pharmacogenomic analysis of tacrolimus in pediatric living-donor liver transplant recipients.

OBJECTIVE: Our objective was to investigate the population pharmacokinetics of tacrolimus in pediatric living-donor liver transplant recipients and examine the effects of the multidrug resistance 1 (MDR1) gene and the cytochrome P450 (CYP) genes CYP3A4 and CYP3A5 on the oral clearance of tacrolimus. METHODS: Data were collected retrospectively from 130 de novo pediatric liver transplant recipients treated with tacrolimus during the first 50 postoperative days. Pharmacogenomic data including both the CYP3A5*3 polymorphism and messenger ribonucleic acid (mRNA) expression levels of MDR1, CYP3A4, and CYP3A5 in the native intestine and the graft liver at transplantation were obtained from 65 of the recipients. Population pharmacokinetic analysis was performed with the nonlinear mixed-effects modeling program NONMEM to estimate population mean parameters of apparent clearance (CL/F) and apparent volume of distribution (V/F). RESULTS: Both CL/F and V/F were allometrically related to body weight, and CL/F decreased when the AST value was elevated. CL/F increased linearly in the immediate postoperative period but did not change with time after postoperative day 21. The intestinal MDR1 mRNA level significantly influenced the initial CL/F (P < .005). Furthermore, the increase in CL/F over time was 2 times higher (95% confidence interval, 1.19-2.81 times; P < .005) in recipients of a CYP3A5*1-carrying graft liver than in patients with the hepatic CYP3A5*3/*3 genotype. The Bayesian prediction for tacrolimus concentrations was not significantly biased on any postoperative day, and the mean absolute prediction error was lower than 3 ng/mL after the first 2 weeks of transplantation. CONCLUSIONS: The enterocyte MDR1 mRNA level and the CYP3A5*1 allele in the graft liver contribute differently to the interindividual variability in the oral clearance of tacrolimus after living-donor liver transplantation.

Adolescent↗

PubMed2006

Effect of intestinal CYP3A5 on postoperative tacrolimus trough levels in living-donor liver transplant recipients.

It has been reported that hepatic and intestinal cytochrome P450 (CYP) 3A4, CYP3A5 and P-glycoprotein affect the pharmacokinetics of tacrolimus, and that these proteins are associated with the large inter-individual variation in the pharmacokinetics of this drug. We previously showed that the concentration/dose ratio of tacrolimus tended to be lower in recipients of living-donor liver transplantation (LDLT) with a CYP3A5*1/*1-carrying graft. However, the effect of intestinal CYP3A5 remains to be elucidated. In the present study, we examined the CYP3A5 genotype in both recipients and donors, and the effect of the recipients' polymorphism on the concentration/dose ratio of tacrolimus in patients after LDLT. The CYP3A5*3 allele frequency was 80% in recipients and 77% in donors. The intestinal CYP3A5 mRNA expression level was significantly associated with genotype. The tacrolimus concentration/dose ratio was lower in recipients with the CYP3A5*1/*1 and *1/*3 genotype (CYP3A5 expressors) compared to the CYP3A5*3/*3 genotype (non-expressors). Amongst the combination of CYP3A5 genotypes between the graft liver and the native intestine, CYP3A5 expressors in both the graft liver and the native intestine had the lowest concentration/dose ratio of tacrolimus during 35 days after LDLT. Patients with the intestinal CYP3A5*1 genotype tended to require a higher dose of tacrolimus compared to the other group with the same hepatic CYP3A5 genotype. These results indicate that intestinal CYP3A5, as well as hepatic CYP3A5, plays an important role in the first-pass effect of orally administered tacrolimus.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2006

Evaluation of Calvert's formula for dosage adjustment of carboplatin in Japanese patients with hormone refractory prostate cancer.

For hormone refractory prostate carcinoma, a combination therapy of paclitaxel and carboplatin is used to expect life extension. We investigated the pharmacokinetics of carboplatin in Japanese prostate cancer patients (n=10, 55-72 years), and evaluated the usefulness of Calvert's formula in the individualized dosing adjustment. They were intravenously administered carboplatin (area under the free plasma concentration versus time curve (AUC)=5 mg.min/ml), following the intravenous administration of paclitaxel (175 mg/m(2)). The dosage of carboplatin for each patient was determined with Calvert's formula using individual creatinine clearance values. Plasma concentration of total platinum was measured sequentially and the pharmacokinetic parameters of carboplatin were determined in each patient. Plasma concentration of total carboplatin after intravenous infusion well fitted the two-compartment model. Carboplatin clearance was 62.0+/-12.7 ml/min (mean+/-S.D.), and linearly related to the individual creatinine clearance (r(2)=0.64, p<0.01). The actual AUC for total carboplatin was 8.20+/-1.11 mg.min/ml, and its inter-individual variability was decreased to 65% of that in carboplatin clearance, indicating the effectiveness of Calvert's formula for dosage adjustment of carboplatin. Leucopenia of grade 4 according to the National Cancer Institute's Common Toxicity Criteria was found in one patient, but no patient demonstrated thrombocytopenia. In conclusion, determining carboplatin dosage based on Calvert's formula decreased the inter-individual variability in the actual AUC compared with that in the carboplatin clearance, and a target AUC of 5 mg.min/ml of carboplatin was comparatively safe for Japanese patients with prostate cancer.

Aged↗

PubMed2006

Delayed effect of grapefruit juice on pharmacokinetics and pharmacodynamics of tacrolimus in a living-donor liver transplant recipient.

Tacrolimus is a calcineurin inhibitor that has been widely used to prevent allograft rejection after transplantation. We report a case of a living-donor liver transplant recipient experiencing a considerable increase in the trough blood concentration of tacrolimus after concomitant ingestion of grapefruit juice (250 mL) 4 times for 3 days. The trough blood concentrations of tacrolimus were not changed during or immediate after the repeated intake of grapefruit juice. However, almost 1 week after the final ingestion, the blood concentration of tacrolimus markedly increased to as much as 47.4 ng/mL from 4.7 ng/mL before the ingestion, resulting in a profound reduction of calcineurin phosphatase activity in peripheral blood mononuclear cells. Furthermore, headache and nausea, but not nephrotoxicity or hyperglycemia, took place throughout the period of the elevated blood concentrations. Grapefruit juice may have a clinically significant effect on the pharmacokinetics and pharmacodynamics of tacrolimus. It is recommended to avoid the consumption of grapefruit juice in transplant recipients treated with tacrolimus.

Adult↗

PubMed2006

Temporal decline in sirolimus elimination immediately after pancreatic islet transplantation.

Pancreatic islet transplantation is a curable treatment for type 1 diabetes and has been put into practice in various countries. In this study, we analyzed the pharmacokinetic characteristics of sirolimus and tacrolimus in six Japanese patients with pancreatic islet transplants immediately after surgery, and monitored efficacy and toxicity. The patients were treated with immunosuppressive therapy based on the Edmonton protocol, that is, sirolimus and low-dose tacrolimus. Pharmacokinetic analyses were performed using the nonlinear mixed-effects modeling program NONMEM. Large inter- and intra-individual variability was observed in the pharmacokinetics of sirolimus and tacrolimus. A model with increased apparent clearance in the postoperative period explained well the intra-individual variability in the pharmacokinetics of both drugs. The most frequent drug-induced toxicity was a decrease in the white blood cell count, and two of six patients required the administration of granulocyte colony-stimulating factor. Clinical laboratory tests immediately before the transplantation and cytochrome P450 3A5 genotype were not related to the high blood concentrations of sirolimus after the loading dose. From these results, the apparent clearance of sirolimus and tacrolimus might temporally decline immediately after pancreatic islet transplantation. A high trough concentration of sirolimus might increase the risk of hematological toxicy, and adjustment of the dosage for immunosuppressive treatment will be necessary in Japanese patients.

Adult↗

PubMed2006

Repeated intravenous injection of recombinant human hepatocyte growth factor ameliorates liver cirrhosis but causes albuminuria in rats.

Hepatocyte growth factor (HGF) is a promising agent for the treatment of liver cirrhosis because of its mitogenic and anti-fibrotic effects. We investigated the effect of recombinant human HGF (rh-HGF) on cirrhosis development; its pharmacokinetics and nephrotoxicity in rats with liver cirrhosis induced by 4-week treatment with dimethylnitrosamine (DMN). rh-HGF (0.3 mg/kg) was intravenously administered to rats once a day for 4 weeks in parallel with DMN treatment or twice a day for the last 2 weeks of DMN treatment. Repeated doses of rh-HGF increased the liver weight and serum albumin, and reduced serum ALT. The development of hepatic fibrosis was inhibited more efficiently by extended low-dose treatment with rh-HGF. In cirrhotic rats, serum levels of rh-HGF increased and clearance was decreased, leading to an increase in the area under the plasma-concentration time curve and a decrease in the steady-state volume of distribution. Repeated doses of rh-HGF led to increased urinary albumin excretion, but no rh-HGF-treated animals developed increased serum creatinine levels. Urinary albumin excretion returned to baseline after the cessation of rh-HGF. These results suggest that extended treatment with rh-HGF is required for the attenuation of cirrhosis, and repeated doses of rh-HGF cause adverse effects in extra-hepatic organs. These issues must be resolved before the widespread application of rh-HGF in the treatment of liver cirrhosis.

Alanine Transaminase↗

PubMed2005

Prediction of glycylsarcosine transport in Caco-2 cell lines expressing PEPT1 at different levels.

H(+)-coupled peptide transporter 1 (PEPT1) and the basolateral peptide transporter mediate the absorption of small peptides and peptide-like drugs in the small intestine. Recently, we constructed a mathematical model to simulate glycylsarcosine (Gly-Sar) transport in Caco-2 cells. In this study, we attempted to adjust our model to a change in the expression level of PEPT1. To obtain cell lines expressing PEPT1 at different levels, recloning of Caco-2 cells was performed, and nine clones were isolated. Compared with parental cells, clones 1 and 9 exhibited the lowest and the highest levels of [(14)C]Gly-Sar uptake from the apical side, respectively, whereas activities of the basolateral peptide transporter were comparable. Kinetic analysis demonstrated that the difference in the activity of PEPT1 was accounted by variations in V (max). Moreover, PEPT1 mRNA level was positively related to the activity of [(14)C]Gly-Sar uptake (r=0.55). Based on these findings, the V (max) value of PEPT1 was defined as a variable using the amount of PEPT1 mRNA as an index of the expression level. With this improved model, Gly-Sar transport in clones 1 and 9 was well-predicted, suggesting that our model can simulate Gly-Sar transport in cells expressing PEPT1 at different levels.

Biological Transport↗