論文 - 大谷　壽一

Inhibition of P-glycoprotein by flavonoid derivatives in adriamycin-resistant human myelogenous leukemia (K562/ADM) cells

Ikegawa T., Ohtani H., Koyabu N., Juichi M., Iwase Y., Ito C., Furukawa H., Naito M., Tsuruo T., Sawada Y.

Cancer Letters （Cancer Letters）  177 （ 1 ） 89 - 93 2002年03月

ISSN  03043835

　概要を見る

We investigated the effects of natural flavones, quercetin and morin, and their pentamethyl, pentaethyl, pentapropyl, pentabutyl and pentaallyl ethers, on the function of P-glycoprotein (P-gp) assessed by an increase in the uptake of [3H]vincristine by human myelogenous leukemia (K562) cells and adriamycin-resistant human myelogenous leukemia (K562/ADM) cells. Pentamethyl, pentaethyl, pentapropyl and pentaallyl ethers of morin and quercetin (20 μM) all increased the uptake of [3H]vincristine by K562/ADM cells, while quercetin, morin and their pentabutyl ethers had no effect. Pentamethylquercetin, pentaallylquercetin and pentaethylmorin remarkably increased the uptake of [3H]vincristine by K562/ADM cells by 10.6, 10.8 and 14.4-fold, respectively. These inhibitory potencies for P-gp were more potent than typical P-gp inhibitors, cyclosporine A and verapamil. Taking into consideration that these flavonoid derivatives possess antitumor promoter activity, they may become candidates of effective multidrug resistance-reversing agents in cancer chemotherapy. © 2002 Elsevier Science Ireland Ltd. All rights reserved.

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Proton gradient-dependent transport of valproic acid in human placental brush-border membrane vesicles

Nakamura H., Ushigome F., Koyabu N., Satoh S., Tsukimori K., Nakano H., Ohtani H., Sawada Y.

Pharmaceutical Research （Pharmaceutical Research）  19 （ 2 ） 154 - 161 2002年03月

ISSN  07248741

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Purpose. To investigate the transport mechanism of valproic acid across the human placenta, we used human placental brush-border membrane vesicles and compared them with that of lactic acid. Methods. Transport of [3H]valproic acid and [14C]lactic acid was measured by using human placental brush-border membrane vesicles. Results. The uptakes of [3H]valproic acid and [14C]lactic acid into brush-border membrane vesicles were greatly stimulated at acidic extravesicular pH. The uptakes of [3H]valproic acid and [14C]lactic acid were inhibited by various fatty acids, p-chloromercuribenzene sulfonate, α-cyano-4-hydroxycinnamate, and FCCP. A kinetic analysis showed that it was saturable, with Michaelis constants (Kt) of 1.04 ± 0.41 mM and 1.71 ± 0.33 mM for [3H]valproic acid and [14C]lactic acid, respectively. Furthermore, lactic acid competitively inhibited [3H]valproic acid uptake and vice versa. Conclusion. These results suggest that the transport of valproic acid across the microvillous membrane of human placenta is mediated by a proton-linked transport system that also transports lactic acid. However, some inhibitors differentially inhibited the uptakes of [3H]valproic acid and [14C]lactic acid, suggesting that other transport systems may also contribute to the elevated fetal blood concentration of valproic acid in gravida.

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Ejects of Single and Repeated Treatment with Itraconazole on the Pharmacokinetics of Midazolam in Rats

Sawada Y., Takedomi S., Matsuo H., Ohtani H., Yamano K., Iga T.

Drug Metabolism and Pharmacokinetics （Drug Metabolism and Pharmacokinetics）  17 （ 4 ） 275 - 283 2002年

ISSN  13474367

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To estimate the influence of repeated administration of drug metabolism inhibitors on the extent of drug interaction, we investigated the ejects of single intravenous or repeated oral administration of itraconazole on the pharmacokinetics of midazolam in rats. In the single administration study, the plasma concentration of itraconazole was maintained by intravenous infusion, and midazolam was administered into the portal vein to investigate its kinetics. In the repeated administration study, the kinetics of midazolam was investigated after seven-day oral treatment with itraconazole. The in vitro metabolism of midazolam and the contents of cytochrome P450 were investigated using liver microsomes from the itraconazole-treated rats. © 2002, The Japanese Society for the Study of Xenobiotics. All rights reserved.

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Polymorphism of MDR1 Gene in Healthy Japanese Subjects: A Novel SNP with an Amino Acid Substitution (Glu108Lys)

Honda T., Dan Y., Koyabu N., Ohtani H., Sawada Y., Ieiri I., Otsubo K., Higuchi S.

Drug Metabolism and Pharmacokinetics （Drug Metabolism and Pharmacokinetics）  17 （ 5 ） 479 - 481 2002年

ISSN  13474367

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We discovered a novel single nucleotide polymorphism (SNP) at position 325 (G325A) in exon 5 of the multidrug-resistance 1 (MDR1) gene in a study of 37 healthy Japanese subjects. Details are as follows. SNP, 020614Honda001; GENE NAME, human P-glycoprotein (MDR1); ACCESSION NUMBER, M29427; LENGTH, 25 bases; 5' -ATGAATCTGGAGG/AAAGACATGACCA-3'. This SNP is expected to cause an amino acid substitution (Glu108Lys). In this study, one homozygote and one heterozygote for G325A were identified. © 2002, The Japanese Society for the Study of Xenobiotics. All rights reserved.

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H⁺-linked transport of salicylic acid, an NSAID, in the human trophoblast cell line BeWo

Emoto A., Ushigome F., Koyabu N., Kajiya H., Okabe K., Satoh S., Tsukimori K., Nakano H., Ohtani H., Sawada Y.

American Journal of Physiology - Cell Physiology （American Journal of Physiology - Cell Physiology）  282 （ 5 51-5 ） C1064 - 75 2002年

ISSN  03636143

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We investigated the transport of salicylic acid and L-lactic acid across the placenta using the human trophoblast cell line BeWo. We performed uptake experiments and measured the change in intracellular pH (pHi). The uptakes of [14C] salicylic acid and L-[14C] lactic acid were temperature- and extracellular pH-dependent and saturable at higher concentrations. Both uptakes were also reduced by FCCP, nigericin, and NaN3. Various nonsteroidal anti-inflammatory drugs (NSAIDs) strongly inhibited the uptake of L-[14C] lactic acid. Salicylic acid and ibuprofen noncompetitively inhibited the uptake of L-[14C] lactic acid. α-Cyano-4-hydroxycinnamate (CHC), a monocarboxylate transporter inhibitor, suppressed the uptake of L-[14C] lactic acid but not that of [14C] salicylic acid. CHC also suppressed the decrease of pHi induced by L-lactic acid but had little effect on that induced by salicylic acid or diclofenac. These results suggest that NSAIDs are potent inhibitors of lactate transporters, although they are transported mainly by a transport system distinct from that for L-lactic acid.

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Effects of grapefruit juice and orange juice on the intestinal efflux of P-glycoprotein substrates

Tian R., Koyabu N., Takanaga H., Matsuo H., Ohtani H., Sawada Y.

Pharmaceutical Research （Pharmaceutical Research）  19 （ 6 ） 802 - 809 2002年

ISSN  07248741

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Purpose. The aim of this study is to investigate the effects of 50% ethyl acetate extracts of grapefruit juice (GFJ) and orange juice (OJ) on the transport activity of P-glycoprotein (P-gp) in the rat small intestine. Methods. The efflux of P-gp substrates from rat everted sac in the absence or presence of verapamil, GFJ, OJ or erythromycin was measured. Rhodamine123, fexofenadine and saquinavir were used as P-gp substrates. P-gp expression levels in the rat jejunum and ileum were determined by Western blot analysis. Results. The efflux of rhodamine123 from the everted sac increased from the apex of the jejunum to the low ileum and the expression of P-gp in the ileum was 2.31-fold higher than that in the jejunum. Verapamil and the 50% GFJ and OJ extracts inhibited the efflux from the intestine of all three drugs tested. Erythromycin decreased the efflux of rhodamine123 and fexofenadine, but did not affect the efflux of saquinavir in the intestine. Conclusions. GFJ and OJ extracts inhibited the efflux of P-gp substrates from the small intestine. Therefore, they may enhance the oral bioavailability of P-gp substrates by increasing absorption in the small intestine.

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Transcellular transport of genistein, a soybean-derived Isoflavone, across human colon carcinoma cell line

Oitate M., Nakaki R., Koyabu N., Takanaga H., Matsuo H., Ohtani H., Sawada Y.

Biopharmaceutics and Drug Disposition （Biopharmaceutics and Drug Disposition）  22 （ 1 ） 23 - 29 2001年12月

ISSN  01422782

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Genistein, a soybean-derived isoflavone, is thought to have an anticarcinogenic action, but little is known about the cellular mechanisms of its intestinal absorption. This study was designed to investigate the absorption mechanisms of genistein using human colon carcinoma cell line, Caco-2 cells. The apical-to-basolateral transcellular transport of genistein across a Caco-2 cell monolayer was significantly greater than that in the opposite direction. An uptake experiment revealed that cellular uptake of genistein by Caco-2 cells was concentrative. The transcellular transport of genistein was saturable and temperature-dependent, and was inhibited by other flavonoids such as rutin, quercetin, (+)-catechin and (-)-epicatechin. These results suggest that genistein is transported across Caco-2 cells by a carrier-mediated system, located on the apical membrane. Copyright © 2001 John Wiley & Sons, Ltd.

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Quantitative relationship between myocardial concentration of tacrolimus and QT prolongation in guinea pigs: Pharmacokinetic/pharmacodynamic model incorporating a site of adverse effect

Minematsu T., Ohtani H., Yamada Y., Sawada Y., Sato H., Iga T.

Journal of Pharmacokinetics and Pharmacodynamics （Journal of Pharmacokinetics and Pharmacodynamics）  28 （ 6 ） 533 - 554 2001年12月

ISSN  1567567X

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Clinical cases have been reported of tacrolimus (FK506)-induced QT prolongation. We have previously demonstrated sustained QT prolongation by FK506 in guinea pigs. Herein, we aimed to conduct a pharmacokinetic/pharmacodynamic (PK/PD) analysis of FK506, using a model involving the myocardial compartment. The pharmacokinetics of FK506 and its effects on QTc intervals were investigated in guinea pigs. In the pharmacokinetic study, whole blood and ventricular FK506 concentrations were analyzed, using a 4-compartment model during and after intravenous infusion of FK506 (0.01 or 0.1 mg/hr/kg). Subsequently, the concentration-response relationship between ventricular FK506 concentration and change in QTc interval was analyzed, using the maximal effect (Emax) model. Pharmacokinetic profiles of FK506 showed a delayed distribution of FK506 into the ventricle. Furthermore, the observed QT prolongation paralleled the ventricular FK506 concentrations, with no lag-time between the two. The Emax model successfully described the relationship between changes in QTc interval and ventricular FK506 concentrations. In conclusion, the PK/PD model where the myocardial drug concentration of FK506 was linked with its adverse effect could describe, for the first time, the anti-clockwise hysteresis observed in the relationship between blood FK506 concentration and QT prolongation. Such a hysteresis pattern for QT prolongation might be caused, therefore, mainly by the delayed disposition of FK506 to ventricular myocytes.

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Pharmacokinetic and pharmacodynamic analysis of the antihypercalcemic effect of incadronate disodium in rats

Ohno Y., Yamada Y., Usui T., Takahashi K., Tsuchiya F., Ohtani H., Sato H., Sawada Y., Iga T.

Biological and Pharmaceutical Bulletin （Biological and Pharmaceutical Bulletin）  24 （ 11 ） 1290 - 1293 2001年11月

ISSN  09186158

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Incadronate concentrates into the bone as a target organ after intravenous administration of incadronate disodium. Mature osteoclasts has take up incadronate from the bone surface and convert it from an active to an inactive form. As a result, incadronate decreases the plasma calcium concentration by suppressing bone resorption. In this study, the pharmacokinetic and pharmacodynamic (PK/PD) analysis model for ascertaining the anti-hypercalcemic effects of incadronate disodium was developed in rats. Data on both the concentration of incadronate in bone and that of free calcium in blood after intravenous administration from our previous study were used for analysis. To estimate the concentration in the surface layer of bone, data on the concentration of incadronate in bone after single intravenous administration were analyzed based on the PK model considering three-compartments. The estimated concentrations in the surface layer in bone were applied to the PD model as an input function. The PD model was developed to analyze the changes in the plasma calcium concentration after a single intravenous administration considering an irreversible inhibition of osteoclast activity. The obtained fitted curves were in good agreement with the observed data. The model could explain the long duration of the antihypercalcemic effect of incadronate disodium and should be useful for planning rational dose regimens for effective antihypercalcemic therapy.

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Possibility of the reversal of multidrug resistance and the avoidance of side effects by liposomes modified with MRK-16, a monoclonal antibody to P-glycoprotein

Matsuo H., Wakasugi M., Takanaga H., Ohtani H., Naito M., Tsuruo T., Sawada Y.

Journal of Controlled Release （Journal of Controlled Release）  77 （ 1-2 ） 77 - 86 2001年11月

ISSN  01683659

　概要を見る

For cancer chemotherapy, avoiding the side effects of chemotherapeutic agents is difficult. Multidrug resistance is one of the major obstacles to successful cancer chemotherapy. P-Glycoprotein (P-gp) serves as an efflux pump and plays a key role in the multidrug resistance. We examined the effect of MRK-16, a monoclonal antibody against P-gp, modified liposomes (MRK-Lip) on the human myelogenous leukemia K-562 cells and its adriamycin resistance cell line K-562/ADM cells to avoid the side effects and to reverse the multidrug resistance. The uptake of vincristine (VCR) by K-562/ADM cells was lower than that by K-562 cells. This low uptake was increased in the presence of verapamil and MRK-16, however, it was not increased in the presence of control antibody, IgG2A. The binding of MRK-Lip to K-562/ADM cells was higher than that of IgG2A-modified liposome (IgG-Lip) and liposome without modification (Cont-Lip). Moreover, the cytotoxicity of VCR-encapsulated MRK-Lip to K-562/ADM cells was higher than that of VCR-encapsulated IgG-Lip and Cont-Lip. These results suggest that the interaction between liposomes and multidrug resistance cells was increased by the modification of liposomes with MRK-16. Consequently, the usefulness of MRK-Lip in cancer chemotherapy as a potent carrier was suggested. © 2001 Elsevier Science B.V. All rights reserved.

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Pharmacokinetics and drug interactions of antidepressive agents

Sawada Y., Ohtani H.

Nippon rinsho. Japanese journal of clinical medicine （Nippon rinsho. Japanese journal of clinical medicine）  59 （ 8 ） 1539 - 1545 2001年08月

ISSN  00471852

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Tricyclic antidepressive agents(TCAs) are conventional antidepressant. Cytochrome P450(CYP) 2D6 is involved in the hydroxylation of TCAs, while N-demethylation of TCAs is mediated by other such as CYP2C19, 3A4 and 1A2. The elimination of TCAs is impaired by CYP2D6 inhibitors such as quinidine. Newer antidepressants, selective serotonin uptake inhibitors(SSRIs), are also metabolized in the liver. Fluvoxamine, an SSRI, is a potent inhibitors for CYP1A2 and CYP2C19, moderate for CYP3A4 and weak for CYP 2D6. Paroxetine, another SSRI, causes substantial inhibition of CYP2D6 activity. Milnacipran, a serotonin and noradrenaline reuptake inhibitor, is mainly excreted unchanged in urine and some part as its glucronide conjugate. In contrast to many SSRIs, milnacipran is devoid of metabolic inhibition.

[Pharmacokinetics and drug interactions of antidepressive agents].

Sawada Y, Ohtani H

Nihon rinsho. Japanese journal of clinical medicine 59 （ 8 ） 1539 - 45 2001年08月

ISSN  0047-1852

A comparative pharmacodynamic study of the arrhythmogenicity of antidepressants, fluvoxamine and imipramine, in guinea pigs

Ohtani H., Odagiri Y., Sato H., Sawada Y., Iga T.

Biological and Pharmaceutical Bulletin （Biological and Pharmaceutical Bulletin）  24 （ 5 ） 550 - 554 2001年06月

ISSN  09186158

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Among several classes of antidepressants, tricyclic antidepressants are known to prolong QTc intervals (QT interval corrected by heart rate) in electrocardiograms, while selective serotonin uptake inhibitors (SSRI) are considered to be devoid of arrhythmogenicity. In this study, we aimed to compare the arrhythmogenic potencies of imipramine (IMI), a typical tricyclic antidepressant, and fluvoxamine (FLV), an SSRI, at therapeutic and supratherapeutic concentrations using guinea pigs in vivo. Guinea pigs were anesthetized, and IMI (10 and 20 mg/kg/h) or FLV (20 mg/kg/h) was intravenously administered for 90 minutes to obtain the time-courses of drug concentrations in plasma and the changes in the QTc intervals during and after the drug administration. IMI induced distinct QTc prolongation in a dose-dependent manner, while FLV prolonged QTc intervals only slightly. A pharmacokinetic-pharmacodynamic analysis revealed that the potency for QTc prolongation of IMI was 1.7-fold higher than that of FLV. Taking the therapeutic concentration into account, the clinical risk of FLV for QTc prolongation was suggested to be 5-fold lower than that of IMI. Therefore, this SSRI agent was suggested to be safer than the tricyclic antidepressant for patients with cardiac risk factors, including arrhythmia, or for those taking other arrhythmogenic drugs concomitantly.

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In-vivo kinetics of the interaction between midazolam and erythromycin in rats, taking account of metabolic intermediate complex formation

Takedomi S., Matsuo H., Yamano K., Ohtani H., Sawada Y.

Journal of Pharmacy and Pharmacology （Journal of Pharmacy and Pharmacology）  53 （ 5 ） 643 - 651 2001年05月

ISSN  00223573

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To predict, quantitatively, the extent of drug interaction during repeated administration of a metabolic inhibitor, we analysed the effects of erythromycin treatment under several regimens on the area under the concentration curve (AUC) of midazolam in rats. Midazolam was administered into the portal vein 12 h after erythromycin treatment for 1, 2 or 3 days, or 12, 24, 36, 48, 72 and 96 h after erythromycin treatment for 4 days, and the plasma-concentration profiles of midazolam were analysed to assess the AUC. Moreover, the contents of total cytochrome P450 and inactive metabolic intermediate (MI) complex were simultaneously quantitated. While the AUC value of midazolam was not affected by the administration of erythromycin for 1 day, repeated administration of erythromycin evoked an increase in AUC ratio (AUC in erythromycin-treated rats/AUC in vehicle-treated rats), which reached a maximum value of 1.99 at 12 h after 4 days' treatment with erythromycin. The total content of cytochrome P450 in liver microsomes was unaffected by erythromycin treatment. Although the MI complex was undetectable after 1 day's treatment with erythromycin, its content increased with duration of erythromycin treatment, and the complex disappeared after the end of erythromycin treatment with a half-life of 12.3 h. In conclusion, the interaction between erythromycin and midazolam could be well predicted when the formation of MI complex in the liver was taken into account.

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Prediction of midazolam - CYP3A inhibitors interaction in the human liver from in vivo/in vitro absorption, distribution, and metabolism data

Yamano K., Yamamoto K., Katashima M., Kotaki H., Takedomi S., Matsuo H., Ohtani H., Sawada Y., Iga T.

Drug Metabolism and Disposition （Drug Metabolism and Disposition）  29 （ 4 I ） 443 - 452 2001年04月

ISSN  00909556

　概要を見る

The extent of decreases in apparent hepatic clearance and intrinsic hepatic clearance of midazolam (MDZ) after intravenous administration of MDZ with concomitant oral administration of cimetidine (CIM), itraconazole (ITZ), or erythromycin (EM) was predicted using plasma unbound concentrations and liver unbound concentrations of inhibitors. When MDZ was concomitantly administered with CIM, the observed increase in MDZ concentration was successfully predicted using inhibition constants assessed by human liver microsome and liver-to-plasma unbound concentration ratios in rats. However, the extent of interaction with ITZ or EM was still underestimated even taking into account the concentrative uptake of inhibitors into liver. We could predict the degree of "mechanism-based" inhibition by EM on the hepatic metabolism of MDZ, after repeated administration of EM, by a physiological model incorporating the amount of active enzyme as well as the concentration of inhibitor. The maximum inactivation rate constant and the apparent inactivation constant of EM on MDZ metabolism were 0.0665 min-1 and 81.8 μM, respectively. These kinetic parameters for the inactivation of the enzyme were applied to the physiological model with pharmacokinetic parameters of EM and MDZ obtained from published results. Consequently, we estimated that cytochrome P450 3A4 in the liver after repeated oral administration of EM was inactivated, resulting in 2.6-fold increase in the plasma concentration of MDZ. The estimated extent of increase in MDZ concentration in our study correlated well with the observed value based on metabolic inhibition by EM from published results.

Uptake mechanism of valproic acid in human placental choriocarcinoma cell line (BeWo)

Ushigome F., Takanaga H., Matsuo H., Tsukimori K., Nakano H., Ohtani H., Sawada Y.

European Journal of Pharmacology （European Journal of Pharmacology）  417 （ 3 ） 169 - 176 2001年04月

ISSN  00142999

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Valproic acid is an anticonvulsant widely used for the treatment of epilepsy. However, valproic acid is known to show fetal toxicity, including teratogenicity. In the present study, to elucidate the mechanisms of valproic acid transport across the blood-placental barrier, we carried out transcellular transport and uptake experiments with human placental choriocarcinoma epithelial cells (BeWo cells) in culture. The permeability coefficient of [3H]valproic acid in BeWo cells for the apical-to-basolateral flux was greater than that for the opposite flux, suggesting a higher unidirectional transport in the fetal direction. The uptake of [3H]valproic acid from the apical side was temperature-dependent and enhanced under acidic pH. In the presence of 50 μM carbonyl cyanide p-trifluoromethoxylhydrazone, the uptake of [3H]valproic acid was significantly reduced. A metabolic inhibitor, 10 mM sodium azide, also significantly reduced the uptake of [3H]valproic acid. Therefore, valproic acid is actively transported in a pH-dependent manner on the brush-border membrane of BeWo cells. Kinetic analysis of valproic acid uptake revealed the involvement of a non-saturable component and a saturable component. The Michaelis constant for the saturable transport (Kt) was smaller under acidic pH, suggesting a proton-linked active transport mechanism for valproic acid in BeWo cells. In the inhibitory experiments, some short-chain fatty acids, such as acetic acid, lactic acid, propanoic acid and butyric acid, and medium-chain fatty acids, such as hexanoic acid and octanoic acid, inhibited the uptake of [3H]valproic acid. The uptake of [3H]valproic acid was also significantly decreased in the presence of 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid, salicylic acid and furosemide, which are well-known inhibitors of the anion exchange system. Moreover, p-aminohippuric acid significantly reduced the uptake of [3H]valproic acid. These results suggest that an active transport mechanism for valproic acid exists on the brush-border membrane of placental trophoblast cells and operates in a proton-linked manner. © 2001 Published by Elsevier Science B.V.

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Assessment of systemic adverse reactions induced by ophthalmic β-adrenergic receptor antagonists

Yamada Y., Takayanagi R., Tsuchiya K., Ito K., Ohtani H., Sawada Y., Iga T.

Journal of Ocular Pharmacology and Therapeutics （Journal of Ocular Pharmacology and Therapeutics）  17 （ 3 ） 235 - 248 2001年

ISSN  10807683

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To assess quantitatively the risks of ophthalmic beta-blocking agents for cardiovascular and respiratory adverse reactions, we analyzed the binding kinetics of beta-blocking agents to the beta-1 and beta-2 adrenoceptors. The relationship between the occupancies for beta-1 and beta-2 adrenoceptors and the effects on the exercise pulse rate or the forced expiratory volume in one second (FEV1) after topical administration of carteolol, befunolol, timolol and betaxolol was analyzed using a ternary complex model. The beta-1 and beta-2 receptor occupancies after ophthalmic administration were calculated to be quite high as well as those after oral administration. The maximum occupancies for beta-1 and beta-2 receptors after ordinary ophthalmic administration were 52% and 88% for carteolol, 52% and 61% for befunolol, 62% and 82% for timolol, and 44% and 3% for betaxolol, respectively. Concave relationships were obtained between a decrease in exercise pulse rate and the beta-1 receptor occupancy and between a decrease in FEV1 and beta-2 receptor occupancy, respectively. Nasolacrimal occlusion was estimated to decrease the exercise pulse rate and FEV1 by 65% and 50%, respectively. The beta-1 and beta-2 adrenoceptor occupancies were proved to be the most appropriate indicators for cardiac and pulmonary adverse reactions evoked by ophthalmic beta-blocking agents.

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Characteristics of choline transport across the blood-brain barrier in mice: Correlation with in vitro data

Murakami H., Sawada N., Koyabu N., Ohtani H., Sawada Y.

Pharmaceutical Research （Pharmaceutical Research）  17 （ 12 ） 1526 - 1530 2000年12月

ISSN  07248741

　概要を見る

Purpose. We examined the functional properties of choline transport across the blood-brain barrier (BBB) in mice. We compared the kinetic parameters and transport properties with those found in our in vitro uptake experiments using mouse brain capillary endothelial cells (MBEC4). Methods. The permeability coefficient-surface area product (PS) values of [3H]choline at the BBB were estimated by means of an in situ brain perfusion technique in mice. Results. [3H]Choline uptake was well described by a two-component model: a saturable component and a nonsaturable linear component. The [3H]choline uptake was independent of pH and Na+, but was significantly decreased by the replacement of Na+ with K+. Various basic drugs, including substrates and inhibitors of the organic cation transporter, significantly inhibited the [3H]choline uptake. These in situ (in vivo) results corresponded well to the in vitro results and suggest that the choline transporter at the BBB is a member of the organic cation transporter (OCT) family. Conclusion. The choline transport mechanism at the BBB is retained in MBEC4.

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Quantitative prediction of catalepsy induced by amoxapine, cinnarizine and cyclophosphamide in mice

Nasu R., Matsuo H., Takanaga H., Ohtani H., Sawada Y.

Biopharmaceutics and Drug Disposition （Biopharmaceutics and Drug Disposition）  21 （ 4 ） 129 - 138 2000年12月

ISSN  01422782

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Parkinsonism can be a side effect of antipsychotic drugs, and has recently been reported with peripherally acting drugs such as calcium channel blockers, antiarrhythmic agents and so on. In this study, we examined the quantitative prediction of drug-induced catalepsy by amoxapine, cinnarizine and cyclophosphamide, which have been reported to induce parkinsonism. Dose-dependent catalepsy was induced by these drugs in mice. In vivo dopamine D1, D2 and muscarinic acetylcholine (mACh) receptor occupancies by these drugs in the striatum were also examined. The in vitro binding affinities (Ki values) of amoxapine and cinnarizine to dopamine D1, D2 and mACh receptors in rat striatal synaptic membrane were 200 and 2900 nM, 58.4 and 76.4 nM and 379 and 290 nM, respectively. Cyclophosphamide did not bind to these receptors at concentrations up to 100 μM. Twenty drugs, including those mentioned above, showed a significant correlation between the observed intensity of catalepsy and the values predicted with a pharmacodynamic model (Haraguchi K, Ito K, Kotaki H, Sawada Y, Iga T. Prediction of drug-induced catalepsy based on dopamine D1, D2, and muscarinic acetylcholine receptor occupancies. Drug Metab Disp 1997; 25: 675-684) based on in vivo occupancy of dopamine D1, D2 and mACh receptors. We conclude that occupancy of dopamine D1 and D2 receptors contributes to catalepsy induction by amoxapine and cinnarizine. Copyright © 2000 John Wiley & Sons, Ltd.

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Human placental transport of vinblastine, vincristine, digoxin and progesterone: Contribution of P-glycoprotein

Ushigome F., Takanaga H., Matsuo H., Yanai S., Tsukimori K., Nakano H., Uchiumi T., Nakamura T., Kuwano M., Ohtani H., Sawada Y.

European Journal of Pharmacology （European Journal of Pharmacology）  408 （ 1 ） 1 - 10 2000年11月

ISSN  00142999

　概要を見る

To elucidate the role of P-glycoprotein in human placenta, we examined its expression in placenta, and the transcellular transport and uptake of P-glycoprotein substrates in cultured human placental choriocarcinoma epithelial cells (BeWo cells). The uptake of [3H]vinblastine and [3H]vincristine into BeWo cells was increased in the presence of a metabolic inhibitor, sodium azide. The basolateral-to-apical transcellular transport of [3H]vinblastine, [3H]vincristine and [3H]digoxin was greater than the apical-to-basolateral transcellular transport. In the presence of cyclosporin A, the basolateral-to-apical transcellular transport of [3H]vinblastine, [3H]vincristine and [3H]digoxin was significantly increased, and the apical-to-basolateral transcellular transport was decreased. The uptake of [3H]vinblastine, [3H]vincristine and [3H]digoxin into BeWo cells was significantly enhanced in the presence of several inhibitors, such as verapamil or mouse monoclonal antibody anti-P-glycoprotein MX-MDR (MRK16) as well as cyclosporin A. Although progesterone significantly enhanced the uptake of [3H]vinblastine, [3H]vincristine and [3H]digoxin into BeWo cells, the uptake of [3H]progesterone was not affected by these inhibitors. Immunoblot analysis revealed that P-glycoprotein with a molecular weight of 172 kDa was expressed in BeWo cells and isolated trophoblast cells. Furthermore, P-glycoprotein was detected in human placental brush-border membrane vesicles, but not in human placental basolateral membrane vesicles. In conclusion, these data suggest that P-glycoprotein is expressed on the brush-border membrane (maternal side) of human placental trophoblast cells. P-Glycoprotein is considered to regulate the transfer of several substances including vinblastine, vincristine and digoxin from mother to fetus, and to protect the fetus from toxic substances. (C) 2000 Elsevier Science B.V.

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