Biomedical subjects

A Takadate

Publications and source records attributed to A Takadate.

At least 19 recordsLinked to original sources

PubMed2000

Decreased bilirubin-binding capacity in uremic serum caused by an accumulation of furan dicarboxylic acid.

In chronic renal failure, substances that are effectively excreted in healthy subjects accumulate in serum. These substances, uremic toxins, include a variety of organic acids. It has been reported that a decrease in the bilirubin (BR) binding capacity occurs in the serum of renal failure patients. 3-Carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) has a high affinity for human serum albumin (HSA) and is a potent inhibitor of the serum protein binding of many drugs. We recently reported that CMPF and BR share the binding site for dicarboxylate molecules on the HSA molecule [Pharm Res 1999;16:916-923]. In this study, in order to confirm whether CMPF is involved in the decrease of BR serum binding capacity in chronic renal failure patients, the total concentrations of uremic toxins, CMPF, and indoxyl sulfate (IS) and the free BR concentration in serum from healthy volunteers and renal failure patients were determined. Both total CMPF and IS concentrations correlate with the free BR concentration. However, results from the peroxidase method reveal that IS cannot displace BR under the physiological condition [IS]/[HSA] <1. We, therefore, conclude that CMPF is one of the substances which contribute to the decreased binding capacity of BR in uremic serum.

Adult↗

PubMed2000

Structural features for fluorescing present in methoxycoumarin derivatives.

Structural features of fluorescent methoxycoumarins were examined from the viewpoint of substituent effect and ring structure in connection with intramolecular charge-transfer (ICT). The fluorescence of methoxycoumarins depended primarily upon the ICT from a C6-electron-donating group to the substituents at the C3-position of the coumarin ring. Furthermore, the presence of a lactone ring itself, including a carbonyl group, cyclic ether oxygen and ethylenic bond as partial ring structures, was found to be essential for fluorescing in methoxycoumarins according to the fluorescent behaviors of chemically deformed model compounds.

Chemical Phenomena↗

PubMed1999

Interaction between two dicarboxylate endogenous substances, bilirubin and an uremic toxin, 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid, on human serum albumin.

PURPOSE: Two dicarboxylate endogenous substances, bilirubin (BR) and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF), have a very high affinity to human serum albumin (HSA). This study was undertaken to clarify the existence of a dicarboxylate binding site on HSA. METHODS: Chemical modification, pH dependent binding and X-ray crystallographic analysis were performed to characterize these dicarboxylate binding sites. RESULTS: It was found the binding behavior for dicarboxylates was different from typical site I ligands such as warfarin (WF) and phenylbutazone (PB) and that electrostatic interaction was an important factor for their binding to HSA. Moreover, His residues were considered to play an important role in pH dependent binding of dicarboxylic acids but in a different manner from the site I ligands. X-ray crystallography of CMPF and BR revealed the distances between the two carboxyl groups in their chemical structures were 5.854 A and 9.979 A, respectively. This difference may be reflected in pH dependent binding. Using fluorescent probe displacement, we attempted to identify the binding site for monocarboxylate derivatives of CMPF and investigated the role of individual carboxyl group in the recognition of the binding site. The results suggested two carboxyl groups were important for the specific binding of CMPF to site I. CONCLUSIONS: The binding site for dicarboxylic acids is located in subdomain IIA, which includes site I, on the HSA molecule. Electrostatic interaction is an important driving force for binding to HSA.

Bilirubin↗

PubMed1995

Characterization of binding site of uremic toxins on human serum albumin.

The interaction of uremic toxins including indole-3-acetic acid (IA), indoxyl sulfate (IS), hippuric acid (HA) and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) with human serum albumin (HSA) has been investigated by three methods of fluorescent probe displacement, ultrafiltration and equilibrium dialysis. The binding parameter of CMPF was found to have the strongest affinity (10(7)M-1) among all the uremic toxins studied. Competitive experiment based on the method of Kragh-Hansen suggested that IA, IS and HA bind to site II, whereas CMPF binds to site I. The present limited data indicated that the four uremic toxins caused inhibition to any endo- or exogenous substances on HSA.

Binding Sites↗

PubMed1994

Characterization of region Ic in site I on human serum albumin. Microenvironmental analysis using fluorescence spectroscopy.

Characteristics of region Ic among at least three overlapping binding regions (regions Ia, Ib and Ic) in site I on human serum albumin (HSA) were analysed using n-alkyl p-aminobenzoates (n-alkyl p-ABEs), all of which are specific fluorescent probes for region Ic. In the interaction processes between n-alkyl p-ABEs and HSA, hydrophobic interaction, van der Waals interaction and local structural changes in region Ic were found to be involved based on the results obtained by analyses of the fluorescence spectra, structure-activity relationships and thermodynamic parameters. In addition, comparison of the fluorescence spectra of n-alkyl p-ABEs in HSA and detergents indicated that the possibility of a hydrophobic region Ic around which an amino acid with cationic charge locates could not be denied because of the similarity of fluorescence spectra between n-alkyl p-ABEs in HSA and in neutral and cationic detergents. The deviation of n-alkyl p-ABEs with long alkyl chains (C9-C12) in the relationships between association constants and physicochemical properties of a series of n-alkyl p-ABEs (C1-C12) suggested that region Ic possess an optimal depth. A conformational change of HSA with increasing pH (pH 6-9) generated an increase in hydrophobicity and adaptability of the binding region and made interaction easy, with an increase in adaptability of the binding region Ic; consequently, it enhanced the binding of n-alkyl p-ABEs to HSA.

Binding Sites↗

PubMed1993

Reduction of erythrocyte membrane permeability and protein binding of low-molecular-weight drugs following glycoside derivitization.

The permeability of glycosides (salicin, arbutin, glycyrritin, p-nitrophenyl-beta-D-glucopyranoside, p-nitrophenyl-beta-D-galactopyranoside, p-nitrophenyl-beta-D-lactopyranoside, and p-nitrophenyl-beta-D-maltopyranoside) and their aglycons through human erythrocyte membrane was investigated. The transport rate of the glycosides through human erythrocyte membrane was slower than that of their aglycons. Glycosides with a disaccharide did not permeate the erythrocyte membrane; this observation suggests that the introduction of disaccharide to drugs gives rise to a significant decrease in the leakage of drugs through the erythrocyte membrane. The derivatives of glycosides encapsulated in erythrocytes were not released from these erythrocytes into the outer medium. The transport capacity of the glycosides was not influenced by the kind of suspending medium, but that of the aglycons was influenced by the medium. The glycosides bound to human serum albumin more weakly than their aglycons. Particularly, the glycosides were more difficult to displace from 7-anilinocoumarin-4-acetic acid (site III drug) than their aglycons, except for glycyrritin.

Cell Membrane Permeability↗

PubMed1992

Further characterization of reversal of signs of induced cotton effects of dicumarol derivatives-alpha 1-acid glycoprotein systems by protriptyline.

The interaction of dicumarol derivatives and protriptyline with respect to the binding to alpha 1-acid glycoprotein (AGP) has been investigated by circular dichroism (CD), equilibrium dialysis and ultrafiltration. Investigation of the induced CD spectra of dicumarol derivatives bound to AGP indicated that the conformations of these compounds were different when bound to AGP. Though all the dicumarol derivatives, protriptyline and AGP formed a ternary complex, interaction modes were different, depending upon the substituent groups at position 3 of the dicumarol molecule. On the basis of the protriptyline effect on the CD spectra of all dicumarol derivatives bound to AGP, the compounds were classified in the following way: (1) Dicumarol, ethylidenebis 4-hydroxycoumarin and propylidenebis 4-hydroxycoumarin caused reversal of the sign of ellipticity. This interaction was explained by cooperative binding. (2) Butylidenebis 4-hydroxycoumarin and pentylidenebis 4-hydroxycoumarin generated new band and disappeared ellipticity of the original Cotton effect. This interaction was also explained by the cooperative binding mode. (3) Ethylbiscoumacetate which generated the CD band similar to that of dicumarol in the absence of protriptyline, reversed the sign of the CD spectrum only at 325 nm. The interaction was anticooperative in nature. (4) Benzylidenebis 4-hydroxycoumarin represented type four which had no change in the CD spectrum by the addition of protriptyline. This interaction was explained by the two-state model accompanying the conformational change of AGP. These results suggested that all compounds, except for benzylidenebis 4-hydroxycoumarin, induced negative Cotton effects at 325 nm by taking the same asymmetrical perturbation by the addition of protriptyline and the interaction was carried out according to model 2. An attempt to study the interaction mechanism of two or more drugs with regard to the binding to protein using these models is thought to help in understanding drug-protein interactions.

Binding Sites↗

PubMed1992

Interaction mode of dicumarol and its derivatives with human serum albumin, alpha 1-acid glycoprotein and asialo alpha 1-acid glycoprotein.

The interaction of dicumarol and its seven other derivatives with human serum albumin (HSA), alpha 1-acid glycoprotein (AGP) and desialylatedAGP (asialoAGP) has been investigated by circular dichroism (CD) and fluorescence. The binding parameters of dicumarol and its derivatives obtained from fluorescence almost agreed with those obtained from CD. The binding data indicated that the total binding affinities (nK) to HSA were higher than the binding affinities to AGP and asialoAGP. Hydrophobic interaction was the driving force for the binding to all the three proteins and nK values in the binding process were found to be increased with the increase of hydrophobicity of the compound. This was evidenced by the attempts taken to correlate binding affinities with partition coefficients. Both electrostatic and van der Waals interactions were not found to play any significant role in the binding of these compounds to any of these three proteins. However, in case of the AGP and asialoAGP binding, apart from the hydrophobic interaction, some other forces may be involved as evidenced from the experimental data. Binding was exothermic, entropy driven and spontaneous. The change of enthalpy (delta H degree) was compensated for by the change in entropy (delta S degree). Relative contribution of hydrophobic interactions in the binding of these compounds to HSA was higher than to AGP or asialoAGP. Sialic acid was not found to impart any significant role in the binding of these compounds to AGP.

Asialoglycoproteins↗

PubMed1991

Mobilization of renal and hepatic cadmium by dithiocarbamates in rats.

Sodium N-benzyl-D-glucamine dithiocarbamate (BGD), sodium N-p-hydroxymethylbenzyl-D-glucamine dithiocarbamate (HBGD), sodium N-p-carboxybenzyl-D-glucamine dithiocarbamate (CBGD), and sodium N-p-methoxybenzyl-D-glucamine dithiocarbamate (MeOBGD) were evaluated for their efficacy in the distribution and excretion of cadmium in rats exposed to cadmium. Rats were injected intraperitoneally with 109CdCl2 (1 mg Cd/kg and 74 kBq of 109Cd/one animal) and 30 min or 24 h later, they were injected with chelating agents (400 mumol/kg). At both 30 min and 24 h after treatment with cadmium, these chelating agents all significantly enhanced the biliary excretion of cadmium. At 24 h after cadmium injection, BGD and MeOBGD were the most effective on the biliary excretion of the metal. These chelating agents were effective in mobilizing cadmium from the liver at 30 min after cadmium treatment. At 24 h after cadmium treatment, BGD and MeOBGD significantly depressed cadmium content in the liver. In another experiment, rats were injected intraperitoneally with 109CdCl2 and 3 d later, they were injected with BGD, HBGD, or MeOBGD every other day for 2 weeks. The fecal excretion of cadmium was significantly increased by these chelating agents and MeOBGD was the most effective. The hepatic and renal cadmium contents were significantly decreased after BGD, HBGD or MeOBGD injection. The injection of MeOBGD to rats pretreated with cadmium was more effective than that of BGD, HBGD, or CBGD in removing cadmium from the liver. HBGD injection was more effective in decreasing the cadmium content in the kidney. The treatment with these chelating agents did not cause the redistribution of cadmium to brain, testes, and heart.

Animals↗

PubMed1991

7-Alkylaminocoumarin-4-acetic acids as fluorescent probe for studies of drug-binding sites on human serum albumin.

7-Alkylaminocoumarin-4-acetic acids I-IX having alkylamino groups different in alkylchain lengths were synthesized as fluorescence probes for characterization of drug-binding sites on human serum albumin (HSA). The fluorescences of I-IX were quenched or enhanced in the presence of HSA with shifts of the emission maxima to shorter wavelength. The binding constants and the number of binding sites were determined by the spectral changes of the probes I-IX bound to HSA through analysis of Scatchard's and Job's plots. The primary binding sites of the tested probes were found to be site 2 (diazepam site) on HSA from the results of competitive displacement studies. The polarity of site 2 was estimated from the relationship between the emission maximum of the probe of IV and Z-values, and was found to be comparable to that of acetonitrile. Simple attempts to estimate the site 2 region from the molecular size of the probe of VIII obtained using the Corey-Pauling-Koltun molecular model suggest that the hydrophobic cleft at site 2 is about 21-25 A in depth. The distance between the lone tryptophan residue in HSA and probes bound to site 2 was estimated to be 15-17 A using Förster's equation on the basis of fluorescence energy transfer. The present data suggest that I-IX are useful as fluorescence probes for the characterization of site 2 on HSA.

Acetates↗

PubMed1990

Characterization of drug binding sites on alpha 1-acid glycoprotein.

The classification of drug binding sites on alpha 1-acid glycoprotein (AGP) was studied by displacement experiments using fluorescent probes. Basic drugs not only displaced basic probes strongly but also acidic probes as well. Acidic probes, on the other hand, were displaced by some acidic drugs such as phenylbutazone and sulfadimethoxine which had no effect on most of the basic probes. This contradiction suggests that the basic drugs do not completely share a binding site with the acidic drugs. The polarity of the basic drug binding site was higher than that of the acidic drug binding site. The negative charges were probably located in or near the former, different from the latter. The basic drug binding site was more sensitive to the conformational change of AGP. It seems that there are particular drug binding sites on the AGP molecule for acidic and basic drugs. However, all the displacement data do not fully support the possibility of two independent drug binding sites. Therefore, it is rather reasonable to consider that these sites are not completely separated but are significantly overlapped and influenced by each other. Accordingly, AGP seems to have one wide and flexible drug binding area.

Binding Sites↗

PubMed1989

Effect of N-benzyl-D-glucamine dithiocarbamate on the renal toxicity produced by subacute exposure to cadmium in rats.

The effect of N-benzyl-D-glucamine dithiocarbamate (BGD) on the renal toxicity produced by subacute exposure to cadmium in rats was studied. Rats were injected sc with CdCl2 (1.5 mg Cd/kg) daily for 26 days and thereafter they received 13 injections of BGD (400 mumol/kg) every other day. Urinary protein concentration and AST activity significantly increased after 20 days of cadmium treatment. The pattern of the increase in the urinary excretion of cadmium after cadmium treatment was consistent with that in the urinary excretion of protein and AST. Urinary excretion of amino acid increased gradually after the cessation of cadmium treatment. BGD treatment significantly decreased the urinary excretion of protein, aspartate aminotransferase (AST), and amino acid. Plasma AST activity was elevated 8 days after the beginning of cadmium treatment, indicating that the hepatic damage occurred prior to the renal damage. In addition, the microscopic examination of renal tissue from cadmium-treated rats revealed the necrosis of the proximal tubular cells. The cadmium concentrations in liver and kidney were significantly decreased by BGD treatment. The results of this study indicate that BGD treatment is effective in decreasing the cadmium concentrations in liver and kidney, resulting in the therapeutic effect on the cadmium-induced renal damage.

Amino Acids↗

PubMed1989

Characterization of binding sites for sulfadimethoxine and its major metabolite, N4-acetylsulfadimethoxine, on human and rabbit serum albumin.

In order to gain an understanding of protein binding of sulfadimethoxine (SDM) and its major metabolite, N4-acetylsulfadimethoxine (N4-AcSDM), the binding of SDM and N4-AcSDM to human and rabbit serum albumin (HSA and RSA) was investigated using circular dichroism (CD), fluorescence and dialysis techniques. The CD spectral characteristics of the compounds bound to the albumins suggested that the drug-binding sites on the HSA and RSA had somewhat different asymmetries. The binding constants for SDM-HSA and -RSA interaction were smaller than those for N4-AcSDM. Two specific drug-binding sites were found on RSA, similarly to HSA, from the results of competitive displacement using fluorescence probes. Moreover, SDM and N4-AcSDM were found to share the same first binding site on the albumins. It can be presumed from the displacement data with a series of p-aminobenzoates that the characteristics of the binding sites (such as depth and width of the hydrophobic cleft) for SDM and N4-AcSDM on RSA may be almost the same, but the characteristics of these drug-binding sites on HSA may be somewhat different.

Animals↗

PubMed1988