Synthesis of (22R)-, (22S)-22-Fluoro-, and 22,22-Difluoro-25-hydroxyvitamin D3 and Effects of Side-Chain Fluorination on Biological Activity and CYP24A1-Dependent Metabolism.

Three novel analogues of C22-fluoro-25-hydroxyvitamin D3 (5-7) were synthesized and evaluated to investigate the effects of side-chain fluorination on biological activity and metabolism of vitamin D. These novel analogues were constructed by convergent synthesis applying the Wittig-Horner coupling reaction between CD-ring ketones (41,42,44) and A-ring phosphine oxide (11). The introduction of C22-fluoro units was achieved by stereoselective deoxy-fluorination for synthesizing 5 and 6 or two-step cationic fluorination for 7. The absolute configuration of the C22-fluoro-8-oxo-CD-ring (39) was confirmed by X-ray crystallographic structure determination. The basic biological activity of the side-chain fluorinated analogues, including compounds (5-7), was evaluated. Generally, osteocalcin promoter transactivation activity decreased in the order of C24-fluoro, C23-fluoro, and C22-fluoro analogues. In addition, the metabolic stability of C22-fluoro-25-hydroxyvitamin D3 (5-7) against hCYP24A1 metabolism was also evaluated. 22,22-Difluoro-25(OH)D3 (7) was more stable against hCYP24A1 metabolism compared with its non-fluorinated counterpart 25-hydroxyvitamin D3 (1), but fluorination at the C22 position had little effect on the metabolic stability compared with C24- and C23-fluoro analogues. Our research clarified that side-chain fluorination in vitamin D markedly changes CYP24A1 metabolic stability depending on the fluorinating position.

Synthesis of New 26,27-Difluoro- and 26,26,27,27-Tetrafluoro-25-hydroxyvitamin D3: Effects of Terminal Fluorine Atoms on Biological Activity and Half-life.

As an extension of our research on providing a chemical library of side-chain fluorinated vitamin D3 analogues, we newly designed and synthesized 26,27-difluoro-25-hydroxyvitamin D3 (1) and 26,26,27,27-tetrafluoro-25-hydroxyvitamin D3 (2) using a convergent method applying the Wittig-Horner coupling reaction between CD-ring ketones (13, 14) and A-ring phosphine oxide (5). The basic biological activities of analogues, 1, 2, and 26,26,26,27,27,27-hexafluoro-25-hydroxyvitamin D3 [HF-25(OH)D3] were examined. Although the tetrafluorinated new compound 2 exhibited higher binding affinity for vitamin D receptor (VDR) and resistance to CYP24A1-dependent metabolism compared with the difluorinated 1 and its non-fluorinated counterpart 25-hydroxyvitamin D3 [25(OH)D3], HF-25(OH)D3 showed the highest activity among these compounds. Osteocalcin promoter transactivation activity of these fluorinated analogues was tested, and it decreased in the order of HF-25(OH)D3, 2, 1, and 25(OH)D3 in which HF-25(OH)D3 showed 19-times greater activity than the natural 25(OH)D3.

Downregulated expression of intestinal P-glycoprotein in rats with cisplatin-induced acute kidney injury causes amplification of its transport capacity to maintain "gatekeeper" function.

The expression of transporters on the apical and basal membranes of renal proximal tubular cells are down- or upregulated to various extents under cisplatin (CDDP)-induced acute kidney injury (AKI). However, little is known about the changes in transporters in tissues other than the kidney under CDDP-induced AKI. This study aimed to investigate the modulation of the expression/function of intestinal efflux transporters, P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp), in CDDP-induced AKI rats. On day 3 after the intraperitoneal administration of CDDP (5 mg/kg) to rats, the expression levels of P-gp and Bcrp were compared with those of normal rats. Further, the absorption of three P-gp substrates (6α-methylprednisolone, rhodamine 123, and gatifloxacin) was evaluated in both groups using conventional loop techniques. In the CDDP-induced AKI rats, P-gp expression in the ileum was markedly decreased to approximately 38% of that in the normal rats. However, no significant changes in Bcrp expression were observed in the AKI rats. In contrast with the reduction in P-gp expression in the AKI rats, the absorption of the three P-gp substrates remained almost the same or decreased in the AKI group. The addition of verapamil (a potent P-gp inhibitor) increased the absorption of the three P-gp substrates to the values obtained from the normal rats. In conclusion, our results suggested that P-gp expression is downregulated in rats with CDDP-induced AKI but that P-gp maintains its potency as a "gatekeeper" against the absorption of xenobiotics by amplifying its individual transport capacity under these conditions.

Influence of Constant Torque Stretching at Different Stretching Intensities on Flexibility and Mechanical Properties of Plantar Flexors.

ABSTRACT: Oba, K, Samukawa, M, Nakamura, K, Mikami, K, Suzumori, Y, Ishida, Y, Keeler, N, Saitoh, H, Yamanaka, M, and Tohyama, H. Influence of constant torque stretching at different stretching intensities on flexibility and mechanical properties of plantar flexors. J Strength Cond Res 35(3): 709-714, 2021-The purpose of this study was to examine the effects of constant torque stretching (CTS) at different stretching intensities on the maximal range of motion (ROM) and muscle-tendon unit (MTU) stiffness of plantar flexors. Fourteen healthy men performed 4 trials of differing stretch intensities: no stretching (control), 50, 75, and 100%. Stretch intensity was defined as maximum passive resistive torque predetermined at a familiarization trial. Each stretch trial consisted of 5 sets of 60-second CTS at the designated stretch intensity. Both maximal ROM and passive resistive torque were assessed during passive dorsiflexion, and MTU stiffness was calculated using the torque-angle curves measured before and after CTS. There were no significant differences in maximal ROM or MTU stiffness at the baseline condition. After the intervention, significantly greater maximal ROM and significantly lower MTU stiffness were observed in the 100% CTS condition than the control condition, whereas there were no significant differences between the submaximal intensity condition (i.e., 50 or 75% intensity) and the control condition. Therefore, our findings suggest that maximal intensity stretching is the most effective approach for improving both flexibility and MTU stiffness with CTS.

[The Usefulness of a Pamphlet for Preventing Exposure to Antineoplastic Agents at Cancer Patients' Homes and an Awareness Survey for Pharmacists about Providing Information to Cancer Patients about Exposure to Antineoplastic Agents].

As the number of patients undergoing outpatient chemotherapy has increased, there is concern that cancer patients' family members are unknowingly exposed to antineoplastic agents at home through cancer patients' excrement or other secreted materials. In this study, we created a pamphlet that introduces several methods to prevent exposure to antineoplastic agents at home and conducted a questionnaire survey to assess the usefulness of the pamphlet. The results indicated that more than 90% of patients believed that the pamphlet was "useful" or "very useful" for ensuring safety with respect to antineoplastic agents at home. Further, most patients responded that the pamphlet decreased their anxieties about their disease and/or treatment. In order to examine pharmacists' involvement in providing information to cancer patients about exposure to antineoplastic agents, we conducted another questionnaire survey, with pharmacists working at Sapporo-Higashi Tokushukai Hospital and Sapporo Tokushukai Hospital. The results indicated that 41 out of 46 pharmacists practiced medication counseling; however, 39 pharmacists did not provide patients with instructions on ways to prevent exposure to antineoplastic agents at home. Their primary reason was a lack of adequate information to do so. Accordingly, the pamphlet prepared in our study would be an effective way to provide guidance for preventing exposure to antineoplastic agents at home.

Investigation on the Interactions between Various Drugs and Aojiru (Green Juice) Using a Simple Centrifugation Method.

The objective of this study was to evaluate the interactions between various drugs and aojiru (green juice), a popular health food in Japan, using a simple centrifugation method. The mixture of drug solution and aojiru suspension was gently shaken and centrifuged. The drug concentration in the supernatant fluid was then determined by HPLC. The concentration of rhodamine 123 (Rho-123), a model compound, in the supernatant fluid significantly decreased after mixing with aojiru, indicating extensive binding of Rho-123 to the insoluble components of aojiru. When administered into rat small intestinal loops together with aojiru, the plasma Rho-123 concentrations became much smaller than those when administered alone. This result strongly suggested that a strong interaction observed in vitro was well reflected in modulated absorption. Among seven drugs tested, chlorpromazine and imipramine exerted binding properties to aojiru similar to or greater than Rho-123. As a small part of both Rho-123 and imipramine was released when the aojiru precipitate was resuspended, their binding to aojiru was considered to be tight. The binding of diltiazem, fexofenadine, glibenclamide, metformin, and norfloxacin to aojiru was much weaker or almost negligible compared with that of chlorpromazine and imipramine. The present results suggest that aojiru can decrease the intestinal absorption of some clinically relevant drugs through tight binding in the small intestine and that the present centrifugation method is useful for predicting in vivo interactions between drugs and aojiru.

Preferential meropenem absorption activated by 1α,25-dihydroxyvitamin D3 and shared with foscarnet, a phosphate transporter substrate, in the rat ileum.

Meropenem (MEPM) is used for the treatment of serious infectious diseases solely as. INJECTABLE: Therefore, the development of an oral formulation would expand its clinical utility. To this end, an exact understanding of the absorption characteristics of MEPM is essential. In this study, MEPM absorption in the rat small intestine was investigated using an in situ loop technique and an in vitro diffusion chamber method. The disappearance ratios of MEPM (0.1 mM) were in the order of ileum > duodenum > jejunum. The extensive MEPM disappearance in the ileum was significantly reduced in the presence of foscarnet, a Na+-dependent phosphate transporter (NaPi-T) substrate, whereas glycylsarcosine, thiamine, taurocholic acid, and biapenem had no effects. The mucosal-to-serosal (M-to-S) permeation of MEPM across the rat ileal segments was very small under normal experimental conditions. However, on addition of 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) to the experimental medium, the M-to-S permeation of MEPM markedly increased, showing a more than 7-fold greater apparent permeation coefficient. The present results suggest that MEPM is preferentially absorbed in the rat ileum, sharing with foscarnet, and that 1,25(OH)2D3 potentially activates the absorption of MEPM there. A likely candidate for involvement in MEPM absorption was NaPi-T or a related transporter.

Development of a magnetic nanoparticle-based method for concentrating SARS-CoV-2 in wastewater.

Several virus concentration methods have been developed to increase the detection sensitivity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in wastewater, as part of applying wastewater-based epidemiology. Polyethylene glycol (PEG) precipitation method, a method widely used for concentrating viruses in wastewater, has some limitations, such as long processing time. In this study, Pegcision, a PEG-based method using magnetic nanoparticles (MNPs), was applied to detect SARS-CoV-2 in wastewater, with several modifications to increase its sensitivity and throughput. An enveloped virus surrogate, Pseudomonas phage φ6, and a non-enveloped virus surrogate, coliphage MS2, were seeded into wastewater samples and quantified using reverse transcription-quantitative polymerase chain reaction to assess the recovery performance of the Pegcision. Neither increasing MNP concentration nor reducing the reaction time to 10 min affected the recovery, while adding polyacrylic acid as a polyanion improved the detection sensitivity. The performance of the Pegcision was further compared to that of the PEG precipitation method based on the detection of SARS-CoV-2 and surrogate viruses, including indigenous pepper mild mottle virus (PMMoV), in wastewater samples (n = 27). The Pegcision showed recovery of 14.1 ± 6.3 % and 1.4 ± 1.0 % for φ6 and MS2, respectively, while the PEG precipitation method showed recovery of 20.4 ± 20.2 % and 18.4 ± 21.9 % (n = 27 each). Additionally, comparable PMMoV concentrations were observed between the Pegcision (7.9 ± 0.3 log copies/L) and PEG precipitation methods (8.0 ± 0.2 log copies/L) (P > 0.05) (n = 27). SARS-CoV-2 RNA was successfully detected in 11 (41 %) each of 27 wastewater samples using the Pegcision and PEG precipitation methods. The Pegcision showed comparable performance with the PEG precipitation method for SARS-CoV-2 RNA concentration, suggesting its applicability as a virus concentration method.

Coupling stimuli-responsive magnetic nanoparticles with antibody-antigen detection in immunoassays.

Because current homogeneous immunoassays show some limitations, particularly low sensitivity, we developed a new immunoassay to overcome these limitations. The approach was based on magnetic nanoparticles with a thermoresponsive polymer layer, a negatively charged polymer, and streptavidin-biotin-based antibody-antigen detection and yielded higher sensitivity than commonly used heterogeneous immunoassays. Because no special equipment is needed, it can be applied to currently available absorbance-based systems for high-throughput assays.

Transgenic overexpression of USP15 in the heart induces cardiac remodeling in mice.

We found a novel protein-protein interaction between ubiquitin-specific protease 15 (USP15) and skeletal muscle LIM protein 1 (SLIM1): USP15 and SLIM1 directly bound under cell-free conditions and co-immunoprecipitated from the lysates of the cells, where they were co-expressed; and USP15 deubiquitinated SLIM1, resulting in the increase of protein levels of SLIM1. Because SLIM1 is strongly implicated in the pathogenesis of myopathies and cardiomyopathies, we generated transgenic (TG) mice with cardiac-specific overexpression of human USP15. Heart weight to body weight ratios and mRNA levels of fetal gene markers in the heart were significantly higher in USP15-TG mice than in wild-type (WT) mice. Also, protein levels of endogenous murine SLIM1 in the heart were significantly higher in USP15-TG mice than in WT mice. Furthermore, the protein of alternatively spliced isoform of SLIM1 was only detected in the heart of USP15-TG mice, and mRNA levels of this isoform were higher as compared to WT mice. These results indicate that USP15 is involved in the regulation of hypertrophic responses in cardiac muscle through transcriptional and post-translational modulation of SLIM1.

Synthesis of C-2 substituted vitamin D derivatives having ringed side chains and their biological evaluation, especially biological effect on bone by modification at the C-2 position.

In order to obtain vitamin D derivatives, which have strong activity for enhancing bone growth, we designed vitamin D derivatives with various substitutions at the C-2 position. Novel 2 α-substituted vitamin D derivatives were synthesized starting from d-glucose as a chiral template of the A-ring with a CD-ring bromoolefin unit using the Trost coupling method. We evaluated these compounds by two in vitro assays, affinity to VDR and transactivation assays, using human osteosarcoma (Hos) cells, and demonstrated the SAR of the C-2 position of VD(3). Furthermore, by using the OVX model, we found that compound 5c, which has a hydroxypropoxy side chain at C-2 and 2,2-dimethyl cyclopentanone in the CD-ring side chain, has a strong activity for enhancing bone growth, same as the reported compound, 2α-(3-hydroxypropoxy)-1α,25-dihydroxyvitamin D(3)1d, and this derivative shows a possibility that calcemic activity is less than 1d in vivo.

[Investigation of Leftover Hyperphosphatemia Drugs in Hemodialysis Outpatients].

Currently, various hyperphosphatemia drugs are administered orally to hemodialysis patients in order to lower serum phosphorus levels. However, it is known that medication adherence is poor, possibly due to greater pill burden taken each time and their complicated schedules. Therefore, large amounts of unused hyperphosphatemia drugs are likely to be leftover. The increase in leftover prescribed drugs leads to the unnecessary elevation of medical care costs. To date, however, the available information on leftover hyperphosphatemia drugs in hemodialysis outpatients is limited. In this study, we performed an interview survey of medication adherence to hyperphosphatemia drugs among 60 hemodialysis outpatients and evaluated the cost of the leftover drugs. Thirty-four patients showed good adherence. On the other hand, 19 patients self-adjusted to take hyperphosphatemia drugs according to their daily diet. When assessing the serum phosphorus levels for these patients over the past year, the values often exceeded the targeted range (3.5-6.0 mg/mL). Furthermore, 35 patients kept hyperphosphatemia drugs at their home. When estimating the cost derived from leftover drugs using the bootstrap method, main distribution of drug cost was shown to be in the range of 2000 to 2500 yen. This drug cost seemed to in part reflect preparation for an emergency. A serious problem was that 14 patients had previous experience in discarding hyperphosphatemia drugs. This study suggested that more appropriate pharmaceutical care according to each patient's situation is essential in improving phosphorus control in hemodialysis outpatients and in reducing the waste of medical resources.

Inhibitory effects of indoxyl sulfate and creatinine on the renal transport of meropenem and biapenem in rats.

Carbapenem antibiotics are excreted preferentially in the urine after intravenous administration, with organic anion transporters (OATs) known to be involved in the renal tubular secretion of carbapenem antibiotics. Various uremic toxins (UTs) accumulate in the blood of patients with end-stage renal failure, and some UTs such as indoxyl sulfate (IS) and creatinine (Cr) are excreted in the urine via OATs. However, information about the possible interactions between these UTs and carbapenems in the renal secretion remains limited. In this study, we investigated the effects of IS and Cr on the renal transport of anionic meropenem and zwitterionic biapenem by using rat renal cortical slices. The uptake of meropenem and biapenem in the renal cortical slices was significantly decreased in the presence of 0.1 mM IS or 1 mM Cr. When biapenem and Cr were co-administered to rats intravenously, biapenem clearance from the plasma was clearly retarded, reflecting the current in vitro results. However, IS and Cr exerted no inhibitory effect on the uptake of metformin, a substrate of renal organic cation transporter (OCT) 2, in the renal cortical slices. Thus, our findings indicate that IS and Cr interfere with the renal secretion of carbapenem antibiotics by preferentially inhibiting OATs.

Downregulated expression of organic anion transporting polypeptide (Oatp) 2b1 in the small intestine of rats with acute kidney injury.

The expression of transporters on the apical and basal membranes of renal tubular cells is modulated under acute kidney injury (AKI). However, little is known about alterations in non-renal transporters in the tissues other than the kidney under AKI situation. This study aimed to assess the modulation of organic anion transporting polypeptide (Oatp) 1a2 and Oatp2b1 expression/function in the small intestine of rats with drug-induced AKI. AKI was induced by intraperitoneal administration of cisplatin at a dose of 5 mg/kg. On day 3 after cisplatin administration, morphological changes in the small intestine, Oatp1a2 and Oatp2b1 expression, and absorption of pravastatin and theophylline were evaluated. Non-negligible atrophy was observed in the jejunum and ileum of the AKI rats. However, the absorption of theophylline was not affected. While intestinal Oatp2b1 expression was markedly decreased in the AKI rats, no alteration was observed in Oatp1a2 expression. The plasma levels of pravastatin after intraluminal administration declined significantly in the AKI rats. However, no such decline was observed after intravenous administration. This study suggested that the responses of intestinal Oatps to experimentally induced AKI was not unidirectional and that pravastatin absorption was governed more potently by Oatp2b1 than by Oatp1a2 in the rat intestine.

[Factors Resulting Correlation and Differences in Renal Function Evaluation Index Using the Serum Cystatin C and Creatinine as Measured by an Enzymatic Method].

We previously reported the association of the estimated glomerular filtration rate (eGFRcreat) calculated from the serum creatinine level (S-Cr) measured using the Jaffe method with the GFR (eGFRcys) estimated from the serum cystatin C level (CysC). However, few studies have compared the eGFRcreat using the enzymatic method with the eGFRcys. It is unclear whether there are differences in the results of renal function assessment. The purpose of this study was to compare the eGFRcreat calculated from the S-Cr with the eGFRcys calculated from the CysC in patients in whom the S-Cr and CysC were simultaneously measured using the enzymatic method, examine the correlations of respective parameters, and clarify physiological factors involved in differences among the parameters. The subjects were 1334 patients treated in 5 institutions. The mean values and correlation coefficient were statistically analyzed using Student's t-test and Pearson's test, respectively. Influential factors between formulae were analyzed using multiple regression analysis. The mean eGFRcreat was 67.0 mL/min/1.73 m2, being significantly higher than the mean eGFRcys (63.2). Multiple regression analysis showed that factors influencing differences in the S-Cr and CysC included the sex, age, serum albumin, and blood urea nitrogen BUN/S-Cr. Furthermore, factors involved in the overestimation of the eGFRcreat in comparison with the eGFRcys included the serum albumin and BUN/S-Cr. The differences between the eGFRcreat calculated from the S-Cr and eGFRcys were less marked than when adopting the Jaffe method in our previous study. However, the eGFRcreat were higher than the eGFRcys in patients with malnutrition or dehydration.

Forefoot and hindfoot kinematics in subjects with medial tibial stress syndrome during walking and running.

Excessive foot pronation during static standing, walking and running has been reported as a contributing factor for the development of medial tibial stress syndrome (MTSS). The motion of foot pronation consists of hindfoot and forefoot motion. However, no previous studies have investigated forefoot and hindfoot kinematics during walking and running in subjects with MTSS. The current study sought to compare hindfoot and forefoot kinematics between subjects with and without MTSS while walking and running. Eleven subjects with MTSS and 11 healthy controls (each group containing 10 males and one female) participated in the current study. Segment angles of the hindfoot and forefoot during walking and running barefoot on a treadmill were recorded using three-dimensional kinematic analysis. An independent t-test was used to compare kinematic data between groups. Subjects with MTSS exhibited significantly greater hindfoot eversion and abduction (p < 0.05) during walking and running than subjects without MTSS, significantly greater forefoot eversion and abduction (p < 0.05) during walking, and significantly greater forefoot abduction during running (p < 0.05). Hindfoot and forefoot kinematics during walking and running were significantly different between subjects with and without MTSS. For prevention and rehabilitation of MTSS, it may be important to focus on not only hindfoot but also forefoot kinematics during both running and walking. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Oncogenic Ras mutant causes the hyperactivation of NF-κB via acceleration of its transcriptional activation.

It is well established that nuclear factor κB (NF-κB) acts as one of the most important transcription factors for tumor initiation and progression, as it both protects cells from apoptotic/necrotic signals and accelerates angiogenesis and tumor metastasis, which is mediated via the expression of target genes. However, it has not yet been clarified how oncogenic signals accelerate the activation of NF-κB. In the current study, we utilized untransformed NIH-3T3 cells stably harboring a κB-driven luciferase gene to show that an oncogenic mutant of Ras GTPase augmented TNFα-induced NF-κB activation. Notably, enforced expression of cyclin-dependent kinase inhibitors, such as p27Kip1 and p21Cip1 , effectively canceled the accelerated activation of NF-κB, suggesting that oncogenic Ras-induced cell cycle progression is essential for the hyperactivation of NF-κB. Furthermore, we found that Ras (G12V) augmented the transcriptional activation of NF-κB, and this activation required the p38 MAP kinase. We observed that a downstream kinase of p38 MAP kinase, MSK1, was activated by Ras (G12V) and catalyzed the phosphorylation of p65/RelA at Ser-276, which is critical for its transcriptional activation. Significantly, phosphorylation of the p65/RelA subunit at Ser-276 was elevated in patient samples of colorectal cancer harboring oncogenic mutations of the K-Ras gene, and the expression levels of NF-κB target genes were drastically enhanced in several cancer tissues. These observations strongly suggest that oncogenic signal-induced acceleration of NF-κB activation is caused by activation of the p38 MAP kinase-MSK1 signaling axis and by cell cycle progression in cancer cells.

Region-dependent absorption of faropenem shared with foscarnet, a phosphate transporter substrate, in the rat small intestine.

Faropenem, a penem antibiotic, is orally active despite its hydrophilic nature. However, its intestinal absorption has not yet been characterised in detail. This study was undertaken to determine the factors regulating faropenem absorption using intestinal loops prepared in the rat duodenum, jejunum and terminal ileum. Faropenem disappearance was much greater than that of cefotaxime and meropenem, and faropenem disappeared more extensively from the terminal ileum than from the jejunum or duodenum. In contrast to faropenem, the disappearance of ceftibuten was much greater from the duodenum and jejunum than from the terminal ileum. As the accumulation and enzymatic degradation of faropenem was minimal in the intestinal mucosa, faropenem was considered to enter the portal vein smoothly after its disappearance from the intestinal loops. Faropenem disappearance was not significantly influenced by the presence of monocarboxylic acids, amino acids or bile acid. Dipeptides such as L-carnosine and glycylglycine slightly but significantly lowered faropenem disappearance from the terminal ileum. On the other hand, foscarnet exerted a marked inhibitory effect on faropenem disappearance, but the antiviral agent did not modulate ceftibuten absorption. The present results suggest that faropenem is in part absorbed via a phosphate transporter present in the rat small intestine.

Relative contribution of absorptive and secretory transporters to the intestinal absorption of fexofenadine in rats.

It has been shown that fexofenadine, a selective non-sedating histamine H(1)-receptor antagonist, is a substrate for P-glycoprotein (P-gp) and an organic anion transporting peptide (OATP). This study was undertaken to investigate the relative contribution of these absorptive and secretory transporters to the intestinal absorption of fexofenadine in rats. When 0.1mM fexofenadine was introduced into duodenal, jejunal, and ileal loops, its disappearance was around 10% over 30 min. Cyclosporine A, but not ketoconazole, probenecid or mitoxantron, significantly increased fexofenadine disappearance in the ileal loops. The serosal-to-mucosal permeation of fexofenadine across the rat ileal segments was approximately 18-fold greater than its mucosal-to-serosal permeation. The secretory orientation of the ileal permeation of fexofenadine was weakened significantly in the presence of cyclosporine A, moderately in the presence of ketoconazole, but was unchanged in the presence of probenecid. When fexofenadine (0.1 or 0.5mM) was administered to rats intraluminally, plasma concentrations increased linearly up to 120 min. The magnitude of the increase in plasma fexofenadine concentrations in the presence of cyclosporine A was more remarkable at 0.5mM than at 0.1mM. The results obtained in this study suggest that the intestinal absorption of fexofenadine is relatively small in rats even if OATP functions as an absorptive transporter for fexofenadine. Low absorption of fexofenadine in rats is attributed to potent secretory transport mediated by P-gp.