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 127 records · Page 7Linked to original sources
PubMed1983

Kinetic aspects and mechanism of liposome disintegration in polyoxyethylene lauryl ether and sodium cholate solutions.

The disintegration behaviour of liposomes in polyoxyethylene lauryl ether (PLE) and sodium cholate solutions was studied by the turbidity disappearance method. In maximally solubilized systems of liposomes, the molar ratios (phosphatidylcholine/surfactant) were 0.43 and 1.8 for PLE and sodium cholate, respectively. The disintegration process of either unilamellar or multilamellar liposomes followed first-order kinetics. Based on a physical model in which liposomes heterogeneous in size were assumed to disintegrate from the outermost shell one by one, a mathematical expression of the turbidity disappearance rate was introduced and applied to explain the data thus obtained. Model calculations suggested that the number of disintegrated shells would not be so large, even if up to 50% reduction of the initial turbidity was observed. From the dependence of the pseudo-first-order rate constant (kobs) on the surfactant concentration for unilamellar liposomes, it was assumed in general that kobs consists of the contributions of the monomer and micellar fractions: for PLE, both fractions shared in the disintegration, but only the micellar fraction with sodium cholate. Furthermore, in the latter case, kobs depended on the initial liposome concentration. These results are likely to be consistent with the proposed modes of surfactant action classified as type A and type B (Helenius, A. and Simons, K. (1975) Biochim. Biophys. Acta 415, 29-79).

Cholic Acid↗
PubMed1986

Depolymerization of solubilized gastric (H+ + K+)-ATPase by n-octylglucoside or cholate.

We have previously shown that an active (H+ + K+)-ATPase can be extracted from gastric apical membranes using n-octylglucoside (Soumarmon, A., Grelac, F. and Lewin, M.J.M. (1983) Biochim. Biophys. Acta 732, 579-585). This extract contained an holomeric enzyme of 390-420 kDa and contained 68% of the K+-stimulated ATPase specific activity originally present. We demonstrate here that inactivation, induced during a more classically designed protocol, is associated with the appearance of smaller, polymorphic structures with molecular mass of 330-360 and 240-250 kDa estimated using molecular sieve chromatography and glycerol gradients. This suggests that (H+ + K+)-ATPase solubilization by n-octylglucoside is a complex process involving first extraction of the enzyme as an active polymer, with subsequent depolymerication and inactivation of this polymer. Depolymerization was specifically studied by treating the large holomeric n-octylglucoside-extracted (H+ + K+)-ATPase with increasing concentrations of either n-octylglucoside or cholate. Detergent-induced changes were characterized by centrifugation on glycerol gradients. Progressive displacement of ATPase activity into three different peaks at 32%, 26% and 20% glycerol was found with increasing detergent concentrations. n-Octylglucoside inhibited enzyme activities and was more deleterious for phosphatase than for ATPase activity. Moreover, it induced the dissociation of phosphatase and ATPase distribution profiles. At concentrations of 0.2 to 1.15%, cholate induced the displacement of the glycerol gradient profiles but no loss of activities and no dissociation of phosphatase and ATPase profiles. Higher concentrations of this detergent (2.5%) also inactivated the ATPase concomitantly with the appearance of a protein peak with no related activity at 16-18% glycerol. From this study we suggest that solubilization of gastric (H+ + K+)-ATPase can be achieved through the extraction of a polymer by n-octylglucoside and through subsequent depolymerization using cholate. We suggest that the different sizes correspond to monomers, dimers, trimers and perhaps tetramers. The monomers were apparently inactive under present test conditions.

4-Nitrophenylphosphatase↗
PubMed1987

A 1H-NMR study of bilirubin IX alpha solubilization by cholate micelles: application of nuclear Overhauser effects.

The solubilization of bilirubin IX alpha in aqueous solution by sodium cholate micelles has been examined by 270 MHz 1H-NMR spectroscopy. Incorporation of bilirubin into the micelles is accompanied by specific shifts of bilirubin vinyl and bridgehead protons and the C18 and C19 methyl groups of the steroid. The observed chemical shifts show a monotonic concentration dependence suggesting that changes in aggregation size are continuous. Nuclear Overhauser effects (NOE) have been shown to be a useful probe or micellization. A 4:1 cholate/bilirubin mixture has been investigated by difference NOE spectroscopy. The observation of intermolecular nuclear Overhauser effects between peripheral protons of bilirubin and cholate are diagnostic of spatially proximate groups. Inter-cholate nuclear Overhauser effects increase in magnitude upon bilirubin incorporation suggesting closer packing of steroid molecules on solubilization of the pigment. Intramolecular nuclear Overhauser effects observed for solubilized bilirubin are consistent with a compact intramolecularly hydrogen-bonded conformation resembling that determined for bilirubin in the solid state.

Bilirubin↗
PubMed1987

High and low affinity binding of [3H]cholate to rat liver plasma membranes.

The transport of bile acids across sinusoidal and canalicular membranes of hepatocytes is characterized as carrier mediated. Such a carrier should specifically bind bile acids at physiological concentrations. We examined the binding of [3H]cholate to rat liver plasma membranes using a microcentrifugation technique and detected high (KD = 1.23 +/- 0.44 microM, Bmax = 21.8 +/- 3.3 pmol/mg protein) and low (KD = 1.97 +/- 1.33 mM, Bmax = 41.5 +/- 25.3 nmol/mg protein) affinity binding sites. Maximal binding was achieved within 15-45 sec and was stable for 2 min at 37 degrees. Binding to the high affinity site was reversible, was not Na+ dependent or attributable to vesicular uptake, and exhibited a broad pH optimum. Binding to this site was negligible or not detected in liver mitochondrial and microsomal fractions, was saturable, and was inhibited by other bile acids. The IC50 values for bile acids as inhibitors of [3H]cholate binding at the high affinity site were: taurocholate, 1.9 nM; glycodeoxycholate, 3.1 nM; chenodeoxycholate, 5.6 nM; taurochenodeoxycholate, 7.3 nM; glycochenodeoxycholate, 11 nM; lithocholate, 13 nM; taurodeoxycholate, 20 nM; glycocholate, 3.6 microM; and deoxycholate, 5.6 microM. [3H]Cholate specific binding was inhibited by 10(-5) M bromosulfophthalein, bilirubin and indocyanin green. These data support the hypothesis that the high affinity binding site represents a carrier which is shared by bile acids and nonbile acid organic anions.

Animals↗
PubMed1988

Mechanisms of membrane protein insertion into liposomes during reconstitution procedures involving the use of detergents. 1. Solubilization of large unilamellar liposomes (prepared by reverse-phase evaporation) by triton X-100, octyl glucoside, and sodium cholate.

The mechanisms governing the solubilization by Triton X-100, octyl glucoside, and sodium cholate of large unilamellar liposomes prepared by reverse-phase evaporation were investigated. The solubilization process is described by the three-stage model previously proposed for these detergents [Lichtenberg, D., Robson, R.J., & Dennis, E.A.(1983) Biochim. Biophys. Acta 737, 285-304]. In stage I, detergent monomers are incorporated into the phospholipid bilayers until they saturate the liposomes. At that point, i.e., stage II, mixed phospholipid-detergent micelles begin to form. By stage III, the lamellar to micellar transition is complete and all the phospholipids are present as mixed micelles. The turbidity of liposome preparations was systematically measured as a function of the amount of detergent added for a wide range of phospholipid concentrations (from 0.25 to 20 mM phospholipid). The results allowed a quantitative determination of RSat, the effective detergent to lipid molar ratios in the saturated liposomes, which were 0.64, 1.3, and 0.30 for Triton X-100, octyl glucoside, and sodium cholate, respectively. The corresponding ratios in the mixed micelles, RSol, were 2.5, 3.8, and 0.9 mol of detergent/mol of phospholipid. The monomer concentrations of the three detergents in the aqueous phase were also determined at the lamellar to micellar transitions (0.18, 17, and 2.8 mM, respectively). These transitions were also investigated by 31P NMR spectroscopy, and complete agreement was found with turbidity measurements. Freeze-fracture electron microscopy and permeability studies in the sublytic range of detergent concentrations indicated that during stage I of solubilization detergent partitioning between the aqueous phase and the lipid bilayer greatly affects the basic permeability of the liposomes without significantly changing the morphology of the preparations. A rough approximation of the partition coefficients was derived from the turbidity and permeability data (K = 3.5, 0.09, and 0.11 mM-1 for Triton X-100, octyl glucoside, and sodium cholate, respectively). It is concluded that when performed systematically, turbidity measurements constitute a very convenient and powerful technique for the quantitative study of the liposome solubilization process by detergents.

Bacteriorhodopsins↗
PubMed1982

Molecular organization in the liquid--crystalline phases of lecithin--sodium cholate-water systems studied by nuclear magnetic resonance.

The molecular organization in the hexagonal and lamellar phases of the ternary systems lecithin--sodium cholate--water has been investigated by using a variety of nuclear magnetic resonance techniques. The main findings and conclusions are the following: (i) When calculated on a mole fraction basis, the phase equilibria are insensitive to changes in the alkyl chains of the lecithin. (ii) When incorporated into a lecithin bilayer, cholate exerts a strong perturbation on the lecithin alkyl chain order, giving a large decrease of the order parameters. (iii) This decrease of the order occurs since the average cross-sectional area per alkyl chain increases probably as a result of cholate placing itself flat on the bilayer surface. (iv) The diffusion of lecithin molecules is approximately equally rapid in the lamellar and hexagonal phases. (v) The hexagonal phase is formed by rodlike aggregates with the polar groups at the surface of the rods and with a continuous hydrocarbon core. The rods are not formed by stacking disklike mixed micelles. (vi) With the interpretations of the molecular packing and the phase structures, the observed phase equilibria are in good agreement with current theories of the factors that govern phase behavior in amphiphile--water systems.

Chemical Phenomena↗
PubMed1978

Reconstitution of 5-hydroxytryptamine transport from cholate-disrupted platelet plasma membrane vesicles.

The bile acid cholate disrupts platelet plasma membrane vesicles and inactivates 5-hydroxytryptamine transport activity. The transporter appears not to be solubilized by this procedure, but remains associated with a high molecular weight aggregate. Merely removing cholate does not restore the vesicular structure or transport activity, but in the presence of added soybean phospholipids, cholate removal generates proteoliposomes which accumulate 5-hydroxytryptamine. This reconstituted transport activity is similar in its ionic requirements and inhibitor sensitivity to transport in native membrane vesicles and intact platelets.

Biological Transport↗
PubMed1996

Fractal analysis of sodium cholate particles.

A fractal analysis was carried out on the powder particles of two samples of sodium cholate. A commercial sample had very irregular particles agglomerated, and accordingly the fractal dimension of the surface was 2.98, suggesting a noteworthy roughness of the particle surface; scanning electron microscopy showed that this was due to irregularities caused by a disordered agglomeration of very small particles, resulting in larger particles showing polygonal and smooth but limited facets. A second sample was obtained by recrystallization from ethanol of the commercial sodium cholate and contained large and regular particles, with very smooth surfaces. The fractal dimension therefore was accordingly low. Despite these differences, the two samples had similar, high reactive dimension values to dissolution (2.96 and 2.76, respectively), suggesting that the surfactant behavior of sodium cholate is an important parameter in driving the dissolution of the solid particles and leveling the surface defects.

Cholic Acid↗
PubMed1984

Studies in bile salt solutions. The effect of pH on the cholate and taurocholate stimulation of human milk lipase catalyzed hydrolysis of p-nitrophenylacetate.

The pseudo-first-order rate constants of hydrolysis of p-nitrophenylacetate, catalyzed by human milk lipase, have been measured in solutions of 0.01 mol dm-3 Bistris(2-[bis(2-hydroxyethyl)amino]-2-(hydroxymethyl)-propane-1,3 -diol) buffer at 310.5 K, containing a range of concentrations of sodium taurocholate and sodium cholate, at pH 8.00 and of sodium cholate at pH 6.5. The effect of pH on the activity of the enzyme has been investigated and the stimulation factors of taurocholate and cholate ions and of cholic acid have been calculated to be equal to 5.3, 3.7 and 10.7, respectively. The essential residues for catalytic activity of the enzyme have ionization constants equal to 6.45-6.46 for pK1 and 8.33-8.40 for pK2. The former value is attributed to the presence of a histidine imidazolium group but the identity of the residue leading to pK2 is not proven.

Catalysis↗
PubMedDate not supplied

The influence of the ionic medium on the behaviour of sodium glycocholate and cholate aqueous solutions.

In the framework of research on the sodium bile salts, solutions of sodium cholate and glycocholate had been studied only at three ionic medium concentrations. In this paper, experiments in two other concentrations of ionic medium are carried out both to verify the behaviour dependence on the ionic medium and to apply the results of this paper to a future investigation on solutions containing contemporary sodium cholate and glycocholate. To this aim, solubility, protonation constants, lead (II) salts solubility products at 25 degrees C and in 0.300 and 0.750 mol dm(-3) N(CH3)4Cl were determined. The formed species in solutions containing lead (II) together with the selected bile salts and the behaviour of the sodium salts in micellar and premicellar solutions were investigated, too. The obtained results were compared with those obtained at the other ionic medium concentrations.

Glycocholic Acid↗
PubMed1998

Chiral separation of polychlorinated biphenyls by micellar electrokinetic chromatography with sodium cholate.

Micellar electrokinetic chromatography (MEKC) with one kind of bile salt (sodium cholate) was used to separate three chiral polychlorinated biphenyls (PCBs; 84, 95, and 176), each one in its two enantiomers. Sodium cholate was used as chiral surfactant in a 2-(N-cyclohexylamino) ethanesulfonic acid (CHES) buffer under alkaline (pH 10) conditions containing urea (2 M). The influence of bile salt concentration on the efficiency and the resolution between the two enantiomers of PCBs 84 and 95 was established. The chiral separation of three PCBs was successfully achieved in less than 30 min (approximately 23 min for PCB 176 and approximately 29 min for PCBs 84 and 95).

1-Propanol↗
PubMed2006

Effects of L-type Ca2+ channel antagonists on in vitro excystment of Paragonimus ohirai metacercariae induced by sodium cholate.

The inhibitory effects of L-type Ca2+ channel antagonists on Na cholate-induced in vitro excystment (CIIE) of Paragonimus ohirai metacercariae were studied. At concentrations of 10 microM, nicardipine and nimodipine inhibited CIIE completely and by approximately 92%, respectively. Nitrendipine and (+/-)-verapamil inhibited CIIE by about one half and one third, respectively. Nifedipine and diltiazem did not inhibit CIIE significantly. At higher concentrations, nitrendipine at 20 microM completely inhibited CIIE, and (+/-)-verapamil at 40 microM inhibited CIIE by 93%. Nifedipine and diltiazem inhibited CIIE only slightly and little, respectively, even at 40 microM. Complete inhibition by nicardipine at 10 microM required preincubation of metacercariae with the antagonist for 15 min. The inhibitory effects of nicardipine and nimodipine were reversible, and most of the nimodipine-treated metacercariae could excyst within 1 h after being washed, but the nicardipine-treated ones started to excyst 1 h after washing. Nicardipine suppressed the active movement of encysted juveniles evoked by Na cholate, whereas nimodipine did not suppress this significantly. These results suggested that L-type Ca2+ channels appeared to be involved in CIIE of P. ohirai metacercariae and that the inhibitory effect of the channels was due primarily to factors other than the inhibition of muscular activity, probably involving the secretion and release of enzymes lytic against the metacercarial cyst wall.

Animals↗
PubMed2006

Sodium dodecyl sulfate promoting a cooperative association process of sodium cholate with bovine serum albumin.

Sodium cholate (NaC) was used as a representative bile salt in the process of cooperative binding to bovine serum albumin (BSA) in a mixture with sodium dodecyl sulfate (SDS). The experiments were performed in 0.02 M Tris-HCl buffer solution (pH 7.50), in the presence of 0.1% BSA and at 25 degrees C. The aim of this study is to provide information on the performance of the BSA in the promotion of cooperative binding of sodium cholate promoted by the presence of SDS. The method used to monitor the binding was based on the analysis of the effect of SDS and NaC concentrations and their mixtures upon the fluorescence intensity of the BSA tryptophan residues. Plots of the fluorescence emission bands in terms of the A0/A ratio vs surfactant concentrations, where A0 and A represent the areas of emission bands in the presence and absence of the surfactants, respectively, were drawn in order to investigate the surfactant interaction with the protein. An alternative methodology, the specific conductivity vs surfactant concentration plots, was used, which involves mixtures of SDS and NaC to investigate the association processes, through the determination of the critical aggregation concentration (cac, when in the presence of protein) and the critical micellar concentration (cmc). The results led to a general conclusion that as the mixed micellar aggregates become richer in the bile salt monomer, the tendency to lose the reactivity with the protein increases. According to our results, a clear evidence of the predomination of BSA-SDS-NaC complexes is found only for the SDS molar fraction above approximately 0.6, and below this fraction a tendency toward free mixed micelles starts to predominate.

Animals↗
PubMed2000

Sodium cholate sorption on cationic dextran hydrogel microspheres. 1. Influence of the chemical structure of functional groups.

New hydrogel microspheres based on crosslinked dextran, containing pendant quaternary ammonium groups with different chemical structures have been synthesized and tested as possible bile acid sorbents The in vitro sodium cholate sorption by these hydrogels has been followed in the absence or in the presence of competing anions The sorption results have indicated a strong influence of the chemical structure of functional groups on both the affinity and selectivity towards cholate ions. The best sorption performances were obtained with hydrogels having in the structure of functional groups an alkyl substituent with the length higher than C(8).

Adsorption↗
PubMed2001

Dietary cholate increases plasma levels of apolipoprotein B in mice by posttranscriptional mechanisms.

To induce atherogenesis in mice, a high fat (HF) diet is supplemented with cholic acid (CA), which increases apoB-containing particles and lower apoA-I-containing particles. HF diet without CA increases levels of both HDL and LDL, suggesting that CA may be responsible for the elevation of LDL and lowering of HDL. The mechanism of dietary CA-induced lowering of apoA-I-containing particles has recently been reported. In this study, we examined the mechanism of CA- and HF-induced elevation of apoB-containing lipoproteins in mice. Mice were fed the following four diets: control chow (C), high fat high cholesterol, (HF), control and 0.5% cholate (CA), and HF+CA. Dietary CA increased the plasma levels of apoB-containing particles by approximately 2-fold when compared to control; VLDL levels increased 2-fold, and LDL levels increased 1.3-fold. On HF diet, VLDL increased by 1.4-fold, and LDL by 2-fold, suggesting that CA and HF-induced increases of apoB-containing particles occurred by different mechanisms. We investigated the potential mechanisms regulating plasma levels of apoB in CA- and HF-fed mice. Although hepatic apoB mRNA levels did not change on CA diet, apoB-100 mRNA increased relative to B-48 as a result of decreased editing of apoB mRNA. Measurements of hepatic LDL receptor mRNA suggested that CA diet down-regulated LDL receptor mRNA, possibly by increasing the levels of hepatic cholesterol. Since plasma and hepatic vitamin E levels did not show significant changes on CA-containing diets, it suggests that dietary CA did not act by increasing the absorption of dietary fat. Hepatic lipase, known to modulate plasma levels of apoB-containing particles, did not show changes in CA- or HF-fed mice. Taken together, these results suggest that dietary CA increased apoB-containing particles both in chow-fed and fat-fed mice by enhancing the relative production of apoB-100, and also by reducing LDL receptor-mediated clearance of apoB-containing particles. Thus, dietary cholate modulates plasma levels of apoB primarily by posttranscriptional mechanisms.

Animals↗
PubMed2005

Oligomeric cholates: amphiphilic foldamers with nanometer-sized hydrophilic cavities.

The hydroxyl at the C-3 of cholic acid was converted to an amino group, and the resulting amino-functionalized cholic acid was used as a monomer to prepare amide-linked oligomeric cholates. These cholate oligomers fold into helical structures with nanometer-sized hydrophilic internal cavities in solvent mixtures consisting of mostly nonpolar solvents such as carbon tetrachloride or ethyl acetate/hexane and 2-5% of a polar solvent such as methanol or DMSO. The conformations of the foldamers were studied by UV, fluorescence, fluorescence quenching, and fluorescence resonance energy transfer. The nature of the polar/nonpolar solvents and their miscibility strongly influenced the folding reaction. Folding was cooperative, as evidenced by the sigmoidal curves in solvent denaturation experiments. The folded conformers became more stable with an increase in the chain length. The folding/unfolding equilibrium was highly sensitive toward the amount of polar solvent. One percent variation in the solvent composition could change the folding free energies by 0.5-1.4 kcal/mol.

Amides↗
PubMed2005

Lipid phase transition in saccharide-coated cholate-containing liposomes: coupling to the surrounding matrix.

We performed FTIR measurements on cholate-containing liposomes (CCL) embedded in saccharide (trehalose or sucrose) matrixes with different contents of residual water. We obtained information on the CCL phase transition following the thermal evolution (310-70 K) of the IR spectrum of the carbonyl moieties of phospholipids in the frequency range 4225-4550 cm(-1). Furthermore, we simultaneously followed the thermal evolution of the water association band, which gave information on the behavior of the surrounding water-saccharide matrix. The analysis revealed a small sub-band of the water association band present in CCL but not in cholate-free liposomes, the thermal evolution of which is tightly coupled to that of the spectrum of the carbonyl moieties of phospholipids. We suggest that this band arises from water molecules, which are inserted within the lipidic structure, in the region located at the border between the hydrophilic and the hydrophobic moieties of phospholipids in the presence of cholic acid. Such water molecules could be responsible for the peculiar flexibility and hydrophilicity of CCL. Following Giuffrida et al. (J. Phys. Chem. B 2003, 107, 13211-13217), we also performed a Spectra Distance analysis, which enabled us to detect an overall liposomes-matrix structural coupling.

Cholates↗
PubMedDate not supplied

Increased serum concentrations of secondary bile salts during cholate feeding are due to coprophagy. A study with wild-type and Atp8b1-deficient mice.

Coprophagy (i.e., consumption of feces) is a behavior seen in rodents and other animal species. This behavior can substantially influence the enterohepatic cycling of compounds, including bile salts. Since many studies involve the feeding of rodents with bile salt supplemented diets, it is of importance to know the influence of coprophagy on bile salt composition in such studies. We compared the peripheral and portal bile salt composition of mice in conventional and metabolic cages when fed a control diet or a diet containing 0.5% cholate. We also performed these experiments with Atp8b1-deficient mice as it has been suggested that in the absence of this transporter bile salt absorption in the intestine would be increased. In mice on a control diet there is little difference in bile salt composition between conventional housing and metabolic housing. Metabolic housing led to a near complete disappearance of the low levels of dihydroxy bile salts (i.e., deoxycholate + chenodeoxycholate) in peripheral serum. In mice fed a control diet, the portal blood concentration of unconjugated dihydroxy bile salts was extremely low (<2%), but these rose to about 10% when mice were fed a cholate-supplemented diet. In metabolic cages the portal blood content of these unconjugated dihydroxy bile salts was reduced to undetectable levels. Whether housed in conventional cages or in metabolic cages, wild-type and Atp8b1-deficient mice had similar concentrations in portal blood, suggesting that intestinal bile salt absorption is not altered in Atp8b1-deficient mice.

Adenosine Triphosphatases↗