Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cholates”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 955 records · Page 53Linked to original sources
PubMed1999

Substrates of multidrug resistance-associated proteins block the cystic fibrosis transmembrane conductance regulator chloride channel.

1. The effects of physiological substrates of multidrug resistance-associated proteins (MRPs) on cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel currents were examined using patch clamp recording from CFTR-transfected mammalian cell lines. 2. Two MRP substrates, taurolithocholate-3-sulphate (TLCS) and beta-estradiol 17-(beta-D-glucuronide) (E217betaG) caused a voltage-dependent block of macroscopic CFTR Cl- currents when applied to the intracellular face of excised membrane patches, with mean apparent dissociation constants (KDs) of 96+/-10 and 563+/-103 microM (at 0 mV) respectively. The unconjugated bile salts taurocholate and cholate were also effective CFTR channel blockers under these conditions, with KDs of 453+/-44 and 3760+/-710 microM (at 0 mV) respectively. 3. Reducing the extracellular Cl- concentration from 154 to 20 mM decreased the KD for block intracellular TLCS to 54+/-1 microM, and also significantly reduced the voltage dependence of block, by suggesting that TLCS blocks Cl- permeation through CFTR by binding within the channel pore. 4. Intracellular TLCS reduced the apparent amplitude of CFTR single channel currents, suggesting that the duration of block is very fast compared to the gating of the channel. 5. The apparent affinity of block by TLCs is comparable to that of other well-known CFTR channel blockers, suggesting that MRP substrates may comprise a novel class of probes of the CFTR channel pore. 6. These results also suggest that the related proteins CFTR and MRP may share a structurally similar anion binding site at the cytoplasmic face of the membrane.

ATP-Binding Cassette Transporters↗
PubMed2003

The farnesoid X receptor controls gene expression in a ligand- and promoter-selective fashion.

Farnesoid X receptor (FXR) is a nuclear receptor for bile acids. Ligand activated-FXR regulates transcription of genes to allow feedback control of bile acid synthesis and secretion. There are five major bile acids in humans. We have previously demonstrated that lithocholate acts as an FXR antagonist, and here we show that the other four bile acids, chenodeoxycholate (CDCA), deoxycholate (DCA), cholate (CA), and ursodeoxycholate (UDCA), act as selective FXR agonists in a gene-specific fashion. In an in vitro coactivator association assay, CDCA fully activated FXR, whereas CA partially activated FXR and DCA and UDCA had negligible activities. Similar results were also obtained from a glutathione S-transferase pull-down assay in which only CDCA and the synthetic FXR agonist GW4064 significantly increased the interaction of SRC-1 with FXR. In FXR transactivation assays with a bile salt export pump (BSEP) promoter-driven luciferase construct, bile acids showed distinct abilities to activate the BSEP promoter: CDCA, DCA, CA, and UDCA increased luciferase activity by 25-, 20-, 18-, and 8-fold, respectively. Consistently, CDCA increased BSEP mRNA by 750-fold in HepG2 cells, whereas DCA, CA, and UDCA induced BSEP mRNA by 250-, 75-, and 15-fold, respectively. Despite the partial induction of BSEP mRNA, CA, DCA, and UDCA effectively repressed expression of cholesterol 7alpha-hydroxylase, another FXR target. We further showed that all four bile acids significantly increased FXR protein, suggesting the existence of an auto-regulatory loop in FXR signaling pathways. In conclusion, these results suggest that the binding of each bile acid results in a different FXR conformations, which in turn differentially regulates expression of individual FXR targets.

Cell Line↗
PubMedDate not supplied

Transepithelial electrical resistance is not a reliable measurement of the Caco-2 monolayer integrity in Transwell.

The significance of monitoring transepithelial electrical resistance (TEER) value during the study on drug absorption through Caco-2 monolayers in Transwells was re-evaluated. TEER value was monitored before, during, and after the absorption of Streptokinase (45 KD). Four enhancers--disodium ethylenediaminetetracetate (disodium EDTA), sodium cholate (NaC), sodium taurocholate (NaTC), and sodium caprate along with alpha-hemolysin (a cell membrane pore-forming toxin)--were used to signify the outcome of this study. Modified trypan blue exclusion technique was used to examine the Caco-2 cell viability throughout the absorption studies. The enhancers at the used concentration exhibited toxic effect on the Caco-2 cells as evident from the trypan blue exclusion studies. This toxic effect was not reflected by the TEER profile because TEER value dropped after the addition of the absorption enhancers. But it came back to its initial value after the cell culture media was replaced by enhancer-free media. This toxic effect was confirmed by the antiproliferation studies on the four enhancers and alpha-hemolysin against Caco-2 cells. Therefore, we concluded that the measurement of TEER is not a reliable method to determine the absorption enhancers toxicity or integrity of the Caco-2 monolayers in the Transwells.

Adjuvants, Pharmaceutic↗
PubMedDate not supplied

Solubilization and pharmacokinetic behaviors of sodium cholate/lecithin-mixed micelles containing cyclosporine A.

The purpose of this study was to investigate the solubilization capacity of sodium cholate/lecithin-mixed micelles and to evaluate the potential of mixed micelles as a carrier of cyclosporine A for intravenous infusion. The mixed micelles were prepared by coprecipitation technique. The formulation components and preparation procedures, which may affect the solubilization of cyclosporine A, were studied. The dilution stability of cyclosporine A-containing mixed micelles was investigated. Pharmacokinetic behaviors of mixed micelles in rabbits after intravenous infusion were compared with Sandimmun. Results showed the strategies to increase the solubility of cyclosporine A include lowering the molar ratio of sodium cholate to lecithin, increasing the concentration of lecithin, and reducing the ionic strength of the dispersion medium and temperature. The largest solubility was found to be 5.42 +/- 0.16 mg/ml. The leakage of mixed micelles in 5% glucose (5.84%) was much less than that in saline solution (36.7%). The relative bioavailability of mixed micelles versus Sandimmun was 112 +/- 20%, and statistical analysis demonstrated both preparations were bioequivalent. Sodium cholate/lecithin-mixed micelles are promising carriers in the intravenous delivery of cyclosporine A, considering their capability of large-scale production and low-toxic property.

Animals↗
PubMed1999

Uptake of bromosulfophthalein via SO2-4/OH- exchange increases the K+ conductance of rat hepatocytes.

In confluent primary cultures of rat hepatocytes, micromolar concentrations of bromosulfophthalein (BSP) lead to a sizeable hyperpolarization of membrane voltage. The effect is a saturable function of BSP concentration yielding an apparent value of 226 micromol/l and a Vmax of -10.3 mV. The BSP-induced membrane hyperpolarization is inhibited by the K+ channel blocker Ba2+, and in cable-analysis and ion-substitution experiments it becomes evident that the effect is due to a significant increase in cell membrane K+ conductance. Voltage changes were attenuated by the simultaneous administration of SO2-4, succinate, and cholate (cis-inhibition) and increased after preincubation with SO2-4 and succinate (trans-stimulation), suggesting that the effect occurs via BSP uptake through the known SO2-4/OH- exchanger. Microfluorometric measurements reveal that BSP-induced activation of K+ conductance is not mediated by changes in cell pH, cell Ca2+, or cell volume. It is concluded that K+ channel activation by BSP (as well as by DIDS and indocyanine green) may reflect a physiological mechanism linking the sinusoidal uptake of certain anions to their electrogenic canalicular secretion.

Animals↗
PubMed2004

Separation and quantitative recovery of mouse serum arylesterase and carboxylesterase activity.

Paraoxonase-1 (PON1) is known to be associated with high density lipoproteins. We optimized buffer conditions to obtain quantitative recovery of PON1 (arylesterase) activity and analyzed the distribution of PON1 in mice using a combination of size-exclusion chromatography and ultracentrifugation. Size-exclusion chromatography of mouse serum separated the esterase activity into two peaks, one overlapping the high density lipoproteins and a second peak of lower molecular weight, consistent with serum carboxylesterase, which accounted for approximately 20% of the total esterase activity of normal mouse serum. Using conditions for the quantitative recovery of arylesterase activity, we fractionated serum by ultracentrifugation into d < 1.21 g/ml, d < 1.25 g/ml, d > 1.21 g/ml, and d > 1.25 g/ml fractions. We observed that PON1 arylesterase activity and mass were isolated in the d < 1.21 g/ml fraction and that serum carboxylesterase was recovered in the d > 1.25 g/ml fraction. The significance of the confounding of PON1 arylesterase activity by serum carboxylesterase was demonstrated by studying mice challenged with a high-fat, high-cholate diet for 14 days. It was shown that all of the decrease in arylesterase activity in response to this diet is attributable to the HDL-associated arylesterase activity (PON1). We conclude that mouse PON1 is quantitatively associated with high density lipoproteins. The contribution of serum carboxylesterase to the total esterase activity significantly confounds the interpretation of total arylesterase activity in mouse serum.

Administration, Oral↗
PubMed1998

Effects of surfactants on the activity of phospholipase D.

We studied the dependence of the activity of cabbage phospholipase A on the substrate (phosphatidylcholine) the aggregated state of which is regulated by addition of either anionic (sodium dodecyl sulfate, cholate or oleate) or cationic (cetyl-trimethylammonium bromide) surfactants. Activation of the enzyme induced by anionic surfactants was shown to correlate with the size of their polar groups. The phospholipase hydrolase activity correlated with the transformation of multilayer liposomes into micelles. The relationship between the processes was of a complex character. The dependence of the amount of enzymically released choline on the calcium concentration passed through a sharp maximum in the presence of the anionic detergents and monotonically increased in the presence of the cationic detergent. In the former case, the sharp increase in the enzyme activity was suggested to be caused by precipitation of phospholipase D with the anionic detergent calcium salt, which can be considered as a specific type of immobilization.

Animals↗
PubMed2000

Cytochrome P450 1A2: oligomers in proteoliposomes.

The presence of oligomers of cytochrome P450 1A2 in membranes of proteoliposomes produced by the cholate-dialysis technique was demonstrated by cross-linking of protein molecules with bifunctional reagents followed by electrophoretic analysis of the modified proteins. A hexameric organization of cytochrome P450 1A2 in the membrane of proteoliposomes is suggested with high probability based on the comparison of the purified hemoprotein oligomeric structure in an aqueous medium and that in the proteoliposomes. The comparison was carried out using the same method.

Animals↗
PubMed1999

Differential effects of 17alpha-ethinylestradiol on the neutral and acidic pathways of bile salt synthesis in the rat.

Effects of 17alpha-ethinylestradiol (EE) on the neutral and acidic biosynthetic pathways of bile salt (BS) synthesis were evaluated in rats with an intact enterohepatic circulation and in rats with long-term bile diversion to induce BS synthesis. For this purpose, bile salt pool composition, synthesis of individual BS in vivo, hepatic activities, and expression levels of cholesterol 7alpha-hydroxylase (CYP7A), and sterol 27-hydroxylase (CYP27), as well as of other enzymes involved in BS synthesis, were analyzed in rats treated with EE (5 mg/kg, 3 days) or its vehicle. BS pool size was decreased by 27% but total BS synthesis was not affected by EE in intact rats. Synthesis of cholate was reduced by 68% in EE-treated rats, while that of chenodeoxycholate was increased by 60%. The recently identified Delta22-isomer of beta-muricholate contributed for 5.4% and 18.3 % (P < 0.01) to the pool in control and EE-treated rats, respectively, but could not be detected in bile after exhaustion of the pool. A clear reduction of BS synthesis was found in bile-diverted rats treated with EE, yet biliary BS composition was only minimally affected. Activity of CYP7A was decreased by EE in both intact and bile-diverted rats, whereas the activity of the CYP27 was not affected. Hepatic mRNA levels of CYP7A were significantly reduced by EE in bile-diverted rats only; CYP27 mRNA levels were not affected by EE. In addition, mRNA levels of sterol 12alpha-hydroxylase and lithocholate 6beta-hydroxylase were increased by bile diversion and suppressed by EE. This study shows that 17alpha-ethinylestradiol (EE)-induced intrahepatic cholestasis in rats is associated with selective inhibition of the neutral pathway of bile salt (BS) synthesis. Simultaneous impairment of other enzymes in the BS biosynthetic pathways may contribute to overall effects of EE on BS synthesis.

Animals↗
PubMed1999

Thermal analysis characterization of aortic tissues for cardiac valve bioprostheses.

Two multistep extractions were achieved on porcine aortic tissues to obtain acellular matrices used for cardiac bioprostheses. The evaluation of structural modifications and the possible damage of extracellular matrix fibrous proteins were investigated by means of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Protein-water interactions and degradation temperatures were determined by TGA. DSC was used to characterize protein thermal transitions (glass transition and denaturation), which provided information on the dynamic structure of the aortic tissue components. Sodium dodecyl sulfate (SDS) extraction had a destructuring effect, while Triton and cholate treatments did not affect the structural integrity of either elastin and collagen. A DSC comparison showed that SDS destabilizes the collagen triple helical domain and swells the elastin network.

Absorption↗
PubMed1999

Further observations on the uptake and effects of phosphonates in perfused rat liver studied by (31)P-NMR.

We examined the route of uptake of 2-aminoethylphosphonate (NEthPo) and of phenylphosphonate (PhePo; 10 mM each) in perfused liver by (31)P-NMR. Uptake of NEthPo was concentrative. The rate of uptake was reduced to 21 +/- 2% (n = 3; all percentages refer to control rates) by substituting choline for Na(+), and to 21 +/- 4% (n = 3), 32 +/- 6% (n = 5) and 70 +/- 5% (n = 3) by replacing Cl(-) by gluconate, SO(4)(2-) or NO(3)(-), respectively. Taurine (20 mM) reduced NEthPo uptake to 38 +/- 6% (n = 3). The data are consistent with uptake of NEthPo by the Na(+)-coupled Cl(-)-dependent beta-amino acid transporter. A small fraction of NEthPo was incorporated into phospholipid. PhePo uptake evolved over 1 h towards levels of the membrane-permeant volume marker dimethyl methylphosphonate. Uptake depended on H(+), and was inhibited by 4, 4'-diisothiocyanato-stilbene-2,2'-disulphonic acid (100 microM), bumetanide and furosemide (1 mM each) and alpha-cyano-4-OH-cinnamic acid (5 mM) to 31 +/- 4% (n = 4), 28 +/- 4% (n = 4), 27 +/- 5% (n = 6) and 40 +/- 7% (n = 4), respectively. These characteristics of PhePo uptake are reminiscent of H(+)-coupled monocarboxylate transport. The monocarboxylates, lactate and acetate (20 mM), and the substrate analogue, phenylalanine (20 mM), were not inhibitory, while benzoic acid (20 mM) slightly inhibited (to 82 +/- 5%; n = 4) PhePo uptake. The tested phosphonates (10 mM) did not significantly affect hepatic extraction of [(3)H]-cholate or [(3)H]-taurocholate (25 microM each; 1:3 bile salt:albumin). The monocarboxylate analogue, PhePo (10 mM), did not significantly interfere with disposal of lactate (0.3-5 mM).

Aminoethylphosphonic Acid↗
PubMed2000

Cyclodextrin dimers as receptor molecules for steroid sensors.

The dansyl-modified dimer 9 complexes strongly with the steroidal bile salts. Relative to native beta-cyclodextrin, the binding of cholate (1a) and deoxycholate (1b) salts is especially enhanced. These steroids bind exclusively in a 1:1 fashion. For other bile salts (1c-1e) both 1:1 and 1:2 complexes were observed with stabilities similar to those of native beta-cyclodextrin. This indicates that only one cavity is used, with a small contribution from the second. The difference is attributed to the absence of a 12-hydroxy group in the second group of steroids. Comparison with a dimer that lacks the dansyl moiety (6) shows that this group especially hinders the cooperative binding of la and 1b. The smaller interference in the binding of the other steroids indicates that self-inclusion of the dansyl moiety hardly occurs. This weak self-inclusion is supported by fluorescence studies. The dansyl fluorescence of dimer 9 is less blue-shifted than that of other known dansyl-appended cyclodextrin derivatives; this is indicative of a more polar micro-environment. Addition of guests causes a change in fluorescence intensity.

Bile Acids and Salts↗
PubMed2001

Structural consequences of metal complexation of cyclo[Pro-Phe-Phe-Ala-Xaa]2 decapeptides.

The conformational features of both free and Ca2+-complexed cyclo[Pro-Phe-Phe-Ala-Xaa]2 (with Xaa= Glu(OtBu), Lys(CIZ), Leu, and Ala) in solution have been determined by NMR spectroscopy and extensive distance-geometry calculations. The decapeptides are conformationally homogeneous in solution and show common structural features in their free and complexed forms. The structures of the free form contain only trans peptide bonds and are topologically similar to the structure of gramicidin-S, folded up in two antiparallel extended structures, stabilized by interstrand hydrogen bonds, and closed at both ends by two beta-turns. In contrast, the Ca2+-complexed peptides present two cis peptide bonds and are generally similar to those observed for the metal-complexed forms of antamanide and related analogues, folded into a saddle shape with two beta-turns. The Glu(OtBu)-, Leu-, and Lys(ClZ)-containing peptides examined here maintain the biological activity of the cyclolinopeptide A in their ability to competitively inhibit cholate uptake. The natural antamanide and cyclolinopeptide A are both able to inhibit the uptake of bile salts into hepatocytes. They share the same postulated active sequence Pro-Phe-Phe. Based on our structural results, we conclude that the ability to adopt a global conformation, characterized by a clear amphipathic separation of hydrophobic and hydrophilic surfaces, is an important feature for the functioning of this class of peptides.

Biological Transport↗
PubMed2002

Determination of total cholesterol content in food by flow injection analysis with immobilized cholesterol oxidase enzyme reactor.

A new analytical method has been developed--including a new sample preparation procedure--for the automatic determination of total (free and bound) cholesterol in food by flow injection analysis (FIA) with immobilized (cholesterol oxidase) enzyme reactor (IMMER). A suitable sample preparation procedure has been applied to eliminate the problems derived from sensitivity of FIA equipment to common organic solvents used for dissolving of cholesterol: after direct saponification the non-saponificable fraction was dissolved in water phase detergent (sodium cholate) solution. The analytical method is based on the oxidation by cholesterol oxidase followed by the photometric determination of hydrogen peroxide (at 500 nm) using the indicator reaction with peroxidase. The new FIA method was tested for commercial food samples such as whole egg powder and dried pasta. The results were compared with data obtained by GC-determination. It was found that this new procedure is suitable for rapid automated measurement of total cholesterol content in foodstuff and consequently, the FIA technique with immobilized enzyme reactor could be an alternative to the widely used gas-chromatographic (GC) method.

Cholesterol↗
PubMed2000

Separation of naphthalene-2,3-dicarboxaldehyde-derivatized-substance P and its metabolites by micellar electrokinetic chromatography.

This paper describes the development of analytical methodology for the separation of naphthalene-2,3-dicarboxaldehyde (NDA)-derivatized substance P (CBI-SP) and five lysine-containing metabolites by micellar electrokinetic chromatography (MEKC). The effect of surfactant composition and organic modifiers on the separation was investigated. The final separation buffer consisted of 80 mM sodium cholate in 50 mM N-tris (hydroxymethyl)methyl-2-aminoethanesulfonic acid (TES), pH 7. All six lysine-containing peptides were separated under these conditions.

Amino Acid Sequence↗
PubMed2001

Determination of alkylphenol ethoxylates by micellar electrokinetic chromatography with bile salts.

Octyl- and nonylphenol ethoxylates (OPEs and NPEs) with different numbers of ethoxy units (average values: n = 10 and N = 40 for OPEs, and n = 10 for NPEs) were separated by micellar electrokinetic chromatography under positive polarity using an 80 mM borate buffer of pH 8.5 containing sodium deoxycholate (SDC) or sodium cholate (SC). When sodium dodecyl sulfate (SDS) was added to the background electrolyte (BGE) in the absence of the bile salt, a single peak at a migration time longer than that of the EOF was obtained. Substituting the SDS by a bile salt, the homologues were resolved. At the same bile salt concentration, resolution between the homologues was higher with SDC than using SC. Optimum resolution between consecutive homologues was obtained with 50 mM SDC. In the presence of low or moderate amounts of acetonitrile or n-propanol, the background line improved significantly, whereas resolution may increase or decrease slightly. We propose a procedure for the determination of OPEs and NPEs with optimum resolution between the homologues as well as a modified procedure with improved selectivity for the single-run determination of other absorbing nonionic, cationic, and anionic (such as linear alkylbenzene sulfonates) surfactants in industrial and household cleaning products and its application to a variety of samples. The detection limit was ca. 28 microg x mL(-1) of total NPE (n = 10), and peak area repeatabilities at 50 microg x mL(-1) were 1.7% (intraday) and 5.6% (interday).

Bile Acids and Salts↗
PubMed2001

Separation of neutral compounds by microemulsion electrokinetic chromatography: fundamental studies on selectivity.

The selectivity of microemulsion electrokinetic chromatography (MEEKC) was studied utilizing some uncharged model compounds like aromatic amides, steroids, and esters of nicotinic acid. The cosurfactant of the microemulsion was found to be the most important factor affecting the selectivity, and alteration between 6.6% of 1-propanol, 1-butanol, tetrahydrofuran, and 2-ethoxyethanol caused several substantial changes in the migration order. In addition, the nature of the surfactant was found to significantly affect the selectivity. In this case, changes in order of migration was observed by replacement of half the content of sodium dodecyl sulfate (SDS) with either sodium dioctyl sulfosuccinate (SDOSS), 3-(N,N-dimethylmyristylammonio) propanesulfonate (MAPS), polyoxyethylene sorbitan monolaurate (Tween 21), and polyoxyethylene 23 lauryl ether (Brij 35). MEEKC was also accomplished with 3.3% of the anionic surfactant sodium cholate and with the cationic surfactant N-cetyl-N,N,N-trimethylammonium bromide (CTMA). Both provided substantial differences in selectivity as compared to the SDS-based systems. With SDS as surfacant, the concentration was varied within 1.0-4.5%. Minor selectivity changes were observed as the concentration of the surfacant was reduced, but the major effect was a reduction in the total migration time. The organic solvent of the microemulsion droplets was found only to have minor impact on the selectivity.

Chromatography↗
PubMed2002

Solute-solvent interactions in micellar electrokinetic chromatography: IV. Characterization of electroosmotic flow and micellar markers.

A wide study of the compounds and procedures mostly used to determine the electroosmotic flow (EOF) and micelle elution times has been done in seven different micellar electrokinetic chromatography (MEKC) systems. These systems are formed from mixtures of an aqueous buffer with the surfactants sodium dodecyl sulfate, lithium dodecyl sulfate, lithium perfluorooctane sulfonate, sodium cholate, sodium deoxycholate, tetradecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide. The solvation parameter model has been used to evaluate the usefulness of the compounds studied as EOF or micellar markers in each of the seven MEKC systems. It is demonstrated that methanol, acetonitrile and formamide are the best EOF markers, and that dodecanophenone is the best micellar marker.

Chromatography, Micellar Electrokinetic Capillary↗