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 595 records · Page 33Linked to original sources
PubMed1984

A vanadate-stimulated NADH oxidase in erythrocyte membrane generates hydrogen peroxide.

Oxidation of NADH by rat erythrocyte plasma membrane was stimulated by about 50-fold on addition of decavanadate, but not other forms of vanadate like orthovanadate, metavanadate aad vanadyl sulphate. The vanadate-stimulated activity was observed only in phosphate buffer while other buffers like Tris, acetate, borate and Hepes were ineffective. Oxygen was consumed during the oxidation of NADH and the products were found to be NAD+ and hydrogen peroxide. The reaction had a stoichiometry of one mole of oxygen consumption and one mole of H2O2 production for every mole of NADH that was oxidized. Superoxide dismutase and manganous inhibited the activity indicating the involvement of superoxide anions. Electron spin resonance in the presence of a spin trap, 5, 5'-dimethyl pyrroline N-oxide, indicated the presence of superoxide radicals. Electron spin resonance studies also showed the appearance of VIV species by reduction of VV of decavanadate indicating thereby participation of vanadate in the redox reaction. Under the conditions of the assay, vanadate did not stimulate lipid peroxidation in erythrocyte membranes. Extracts from lipid-free preparations of the erythrocyte membrane showed full activity. This ruled out the possibility of oxygen uptake through lipid peroxidation. The vanadate-stimulated NADH oxidation activity could be partially solubilized by treating erythrocyte membranes either with Triton X-100 or sodium cholate. Partially purified enzyme obtained by extraction with cholate and fractionation by ammonium sulphate and DEAE-Sephadex was found to be unstable.

Animals↗
PubMed1987

The enterohepatic circulation of methotrexate in vivo: inhibition by bile salt.

We examined the enterohepatic circulation of methotrexate (MTX) in the rat in vivo and determined the effect of the unconjugated bile salt, cholate, on the process. MTX (70 mg/kg body weight) was administered i. v. and the bile salt (1 mM) was delivered through intestinal perfusion. In the control group 38.43% +/- 4% of the administered dose of MTX appeared in bile 2 h after administration of the drug. In the bile salt-treated group 21.4% +/- 3.7% of the administered doses of MTX appeared in bile, which was significantly lower (P less than 0.01) than the proportion in the control group. The liver content of MTX was depressed by 23% in the bile salt-treated group compared with the control group. This study demonstrates, in vivo, the important role that the enterohepatic circulation plays in exposing the small intestine to toxic levels of MTX and shows that the unconjugated bile salt, cholate, inhibits the process.

Animals↗
PubMed1990

Morpho-cytochemical and biochemical evidence for insulin absorption by the rat ileal epithelium.

In order to investigate the mechanism through which insulin is absorbed by the intestinal epithelium and transferred to the circulation where it exercises its biological activity of lowering blood glucose levels, a combined biochemical morpho-cytochemical study was undertaken on rat ileal tissue, in vivo. Insulin was introduced into the lumen of the ileum in combination with sodium cholate and aprotinin and allowed to be absorbed for various periods of time. Analysis of blood samples from the inferior vena cava, at different time points has demonstrated an increase in plasma insulin followed by a decrease in blood glucose levels. The ileal tissues were studied at different time points after the introduction of the insulin, by applying the protein A-gold immunocytochemical technique. Insulin antigenic sites were detected with high resolution, at various levels of the enterocytes but were absent from goblet cells. At 2 to 5 min, the labelling was mainly associated with the microvilli and endocytotic vesicles in the apical portion of the epithelial cells. Some gold particles were in contact with the lateral membranes. At 10 min, the labelling was found at the level of the trans-side of the Golgi apparatus and mainly along the baso-lateral membranes of the epithelial cells. Labelling was also detected in the interstitial space. The control experiments have demonstrated the specificity of the labelling and confirmed the nature of the insulin molecules detected. Furthermore, the morphological study has confirmed that exposure of the tissue to the insulin-cholate-aprotinin solution does not affect the integrity of the epithelium while promoting insulin absorption.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Bile salts in breast milk.

Breast milk was studied for the presence of bile salts. Cholate and chenodeoxycholate were found in all samples examined. In both colostrum and milk there was a predominance of cholate. Their biological activity remains to be determined.

Bile Acids and Salts↗
PubMed1986

Solubilisation and reconstitution of the rabbit skeletal muscle sarcoplasmic reticulum K+ channel into liposomes suitable for patch clamp studies.

Sarcoplasmic reticulum (SR) membrane vesicles have been prepared from rabbit skeletal muscle and solubilised using K+ cholate. Solubilised membrane proteins were reconstituted into small asolectin liposomes by dialysis against cholate-free solution. Large liposomes were produced by freezing and thawing at -80 degrees C and room temperature, respectively. The liposomes were assayed for the SR K+ channel using the patch clamp technique. Channel density was modulated by varying protein:lipid ratios during reconstitution. Channels inserted into the membrane with a preferred orientation. The solubilised and reconstituted channel behaves ohmically over the holding potential range +/- 70 mV and has a conductance of 178.4 +/- 4.4 pS (mean +/- SE, n = 37) in 200 mM KCl. The channel has a selectivity sequence of K+ greater than NH4+ greater than Rb+ greater than Na+ and K+ conductance is blocked by hexamethonium and decamethonium. The opening probability of the reconstituted channel is voltage dependent. The conductance and gating characteristics displayed by the solubilised and reconstituted channel correlate well with those previously observed following the fusion of native SR membrane vesicles with planar phospholipid bilayers.

Animals↗
PubMed1981

Isolation, characterization, and reconstitution of a solubilized fraction containing the hydrophobic sector of the mitochondrial proton pump.

The hydrophobic sector of the mitochondrial ATPase complex was purified by sequential extraction with cholate and octylglucoside, by further differential solubilization with guanidine and cholate in the presence of phosphatidylcholine, and by fractionation with ammonium sulfate. A polypeptide with a mass of 28,000 dalton was present in the purified hydrophobic section which was cleaved by trypsin, resulting in loss of reconstitution activity. In contrast, dicyclohexylcarbodiimide-binding proteolipid remained unimpaired after exposure to trypsin. The 32Pi-ATP exchange activity of the reconstituted ATPase complex was inhibited by p-hydroxymercuribenzoate, which reacted primarily with the 28,000-dalton protein, as monitored by acrylamide gel electrophoresis with 14C-labeled inhibitor. The function of a 22,000-dalton polypeptide and of some minor components in the region of the proteolipid remains unknown. An examination of the phospholipid requirements for reconstitution of an active complex revealed an unexpected discrepancy. With an excess of phosphatidylethanolamine, optimal reconstitution of 32Pi-ATP exchange and ATP synthesis in the presence of bacteriorhodopsin and light was achieved: at a high phosphatidylcholine:phosphatidylethanolamine ratio, the rate of ATP synthesis remained high, but the rate of 32Pi-ATP exchange dropped precipitously. A new procedure is described for the reconstitution of the ATPase complex with purified phospholipids which is stable for at least 15 days.

Adenosine Triphosphatases↗
PubMed1984

Effects of bile salts on permeability and morphology of main pancreatic duct in cats.

We studied the changes in permeability and morphology in the main pancreatic duct of cats after exposure of the duct to specific bile salts. Cats were anesthetized and the main pancreatic duct was cannulated in the tail and head of the pancreas. The duct was perfused with sodium cholate (1, 1.5, 2, 15 mM) or sodium glycodeoxycholate (1, 2, 15 mM) for 60 min at pressures which never exceeded 20 cm water. Then the duct was perfused with fluorescein-tagged dextran molecules of specific size (3000, 20,000, or 40,000 daltons). Recovery of the dextran from portal venous blood indicated that the duct was permeable to that particular dextran. Normally the ducts were impermeable to even the 3000-dalton dextran, and perfusion with either 1 mM cholate or glycodeoxycholate did not change this. However, perfusion with either bile salt at concentrations above 1 mM progressively increased duct permeability. At this highest bile salt concentrations used, the ducts became permeable to molecules as large as 20,000 daltons. Morphologic changes paralleled the changes in permeability. Control animals had pancreatic ducts whose ultrastructure was indistinguishable from normal. Perfusion of the ducts with low concentrations of bile salt for up to 60 min resulted only in a loss of microvilli from the cell surface and an increase in cytoplasmic phagolysosomes. Perfusion with higher concentrations of bile salt for 5-60 min induced progressively severe alterations. These included disruption of the tight junctions and the swelling of intercellular spaces between the duct cells, flattening of the duct epithelium, and eventual cell loss which left a break in the epithelial lining of the duct. These studies indicate that the pancreatic duct in cats, exposed to specific bile salts at physiological concentrations and pressures, undergoes marked structural alterations. The duct becomes permeable to molecules at least as large as 20,000 daltons, whereas it is normally impermeable to molecules as small as 3000 daltons.

Animals↗
PubMed1992

Bile acid fractionations by high-performance liquid chromatography in equine liver disease.

Serum bile acids were fractionated by high-performance liquid chromatography (HPLC) in 13 control and 8 cases of liver disease in horses. The severity and type of liver injury was determined by histopathological examination of biopsy and/or necropsy specimens. The total serum bile acids (tSBA) were determined in these horses by an enzymatic method (SBA-EA) and by summation of the bile acids (SBA-LC) as fractionated by the HPLC. The SBA-LC were generally higher than the SBA-EA in both the controls and liver disease and they did not parallel each other. The primary bile acids, total cholates and total chenodeoxycholates accounted for most of the tSBA increases in liver disease. There was a shift in profile from taurocholate to free (unconjugated) cholate in direct relation to the severity of the liver injury. Among the secondary bile acids, total deoxycholates and total taurodeoxycholates increased at random. The pattern of the SBA profile in relation to the severity of the liver disease suggested that hepatocellular excretion is the most sensitive step in the enterohepatic circulation of the bile acids.

Animals↗
PubMed1979

[The effect of unconjugated bile salts on the intestinal absorption of electrolytes and water in the proximal jejunum. Studies in conscious rats (author's transl)].

With an in vivo-perfusion-technique the influence of unconjugated bile salts (cholate, desoxycholate) on the net electrolyte and volume absorption is studied in the jejunum of conscious rats. The applied doses correspond to physiological concentrations in the intestine of rats. Control experiments were performed in the same animal. Cholate and desoxycholate diminish the net electrolyte and volume absorption resp. cause a net secretion. The effects are largely reversible. The extent of net volume absorption depends on the applied dose of each bile salt. The possible mode of action of unconjugated bile salts on the electrolyte and water absorption in the small intestine is discussed.

Animals↗
PubMed1988

Evidence for high molecular weight Na-Ca exchange in cardiac sarcolemmal vesicles.

Cardiac sarcolemma (SL) vesicles were subjected to irradiation inactivation-target sizing analyses and gel permeation high performance liquid chromatography (HPLC) to ascertain the weight range of native Na-Ca exchange. Frozen SL vesicle preparations were irradiated by electron bombardment and assayed for Na-Ca exchange activity. When applied to classical target sizing theory, the results yielded a minimum molecular weight (Mr) of approximately 226,000 +/- 20,000 SD (n = 6). SL vesicle proteins were solubilized in 6% sodium cholate in the presence of exogenous phospholipid and fractionated by size on a TSK 30XL HPLC column. Eluted proteins were mixed 1:1 with mobile phase buffer containing 50 mg/ml soybean phospholipid and reconstituted by detergent dilution. The resulting proteoliposomes were assayed for Na-Ca exchange activity. Na-Ca exchange activity eluted in early fractions containing larger proteins as revealed by SDS-PAGE. Recovery of total protein and Na-Ca exchange activity were 91 +/- 7 and 68 +/- 11%, respectively. In the peak fraction, Na-Ca exchange specific activity increased two- to threefold compared to reconstituted controls. Compared to the elution profile of protein standards under identical column conditions, sodium cholate solubilized exchange activity had a minimum Mr of 224,000 Da. Specific 45Ca2+-binding SL proteins with Mr of 234,000, 112,000, and 90,000 Da were detected by autoradiography of proteins transferred electrophoretically to nitrocellulose. These data suggest that native cardiac Na-Ca exchange is approximately 225,000 Da or larger. The exact identification and purification of cardiac Na-Ca exchange protein(s) remains incomplete.

Animals↗
PubMed1989

Expansion of the bile acid pool changes the biliary transport characteristics of centrizonal hepatocytes.

We investigated whether acinar differences in taurocholate transport are responsible for the increased maximal secretory rate observed after expansion of the bile acid pool. The bile acid pool was expanded by cholate feeding for four days. Periportal and centrizonal hepatocytes were then probed by ante- and retrograde liver perfusion, respectively. In control animals, secretory rate constant (alpha 1) averaged 0.439 +/- 0.123 and 0.104 +/- 0.035 min-1 during ante- and retrograde perfusion, respectively, in the absence of exogenous taurocholate. These values did not significantly change when taurocholate was infused. In cholate-fed animals, alpha 1 was comparable during antegrade perfusion but was significantly reduced (0.038 +/- 0.035, p less than 0.05) during retrograde perfusion in the absence of exogenous taurocholate, presumably owing to induction of cytosolic bile acid binding proteins. During loading with exogenous taurocholate, by contrast, alpha 1 was significantly accelerated (0.252 +/- 0.026; p less than 0.01) in centrizonal hepatocytes from bile-acid fed rats. Expansion of the bile acid pool is able to change the bile salt secretory characteristics of centrizonal hepatocytes toward those of periportal ones.

Animals↗
PubMed1993

Phosphatidylcholine as substrate for human pancreatic phospholipase A2. Importance of the physical state of the substrate.

The long-chain phosphatidylcholine/sodium cholate aqueous system as substrate for human pancreatic phospholipase A2 (PLA2) was investigated. At a constant phosphatidylcholine (PC) concentration of 8 mM, the enzyme activity increased with a decrease in cholate (C) concentration up to a PC/C ratio of approximately 0.8 and then rather abruptly decreased to lower values at a ratio above 1.5. At ratios between 0.8 and 1.5, an increasing lag phase in the PLA2 activity was seen, indicating a progressive decrease in substrate availability to the enzyme. Reaction mixtures with a PC/C ratio of up to 0.67 were optically clear solutions composed of mixed bile salt/PC micelles of increasing mixed micellar aggregate size. Ratios between 0.67 and 1.5 were characterized by an increase in turbidity (at 330 and 450 nm) due to increasing formation of vesicles or liposomes. Above a PC/C ratio of 1.5, a sharp increase in turbidity was seen due to increasing formation of bilayer structures other than vesicles. Pure vesicles obtained by dialysis of mixed micellar solutions were not hydrolyzed by the enzyme. Addition of bile salts reversed the inhibition which was accompanied by a decrease in turbidity. Phosphatidylcholine was preferred as substrate for human PLA2 when present in large mixed disc-like bile salt micelles. Vesicular or other types of lamellar liquid-crystalline phases of long-chain phosphatidylcholine did not serve as substrate for PLA2.

Chemical Phenomena↗
PubMed1991

Effects of perturbations in hepatic free and esterified cholesterol pools on bile acid synthesis, cholesterol 7 alpha-hydroxylase, HMG-CoA reductase, acyl-CoA:cholesterol acyltransferase and cytosolic cholesteryl ester hydrolase.

Effects of expansion of the hepatic free cholesterol pool on bile acid and cholesterol metabolism and homeostasis were examined in rats fed cholesterol in high-fat diets or treated with oleyl-p-(n-decyl)-benzenesulfonate (ODS) or progesterone. Cholesterol feeding for 10-16 days, which increased free (33%) and esterified (6-fold) cholesterol, had no effect on cholate synthesis, total bile acid synthesis, or cholate turnover, whereas these activities were increased 60-80% by ODS and progesterone, which produced only small increases (19%) in free cholesterol. Cholesterol feeding reduced beta-hydroxy-beta-methylglutaryl (HMG)-CoA reductase (72%) and cholesteryl ester hydrolase (48%) and increased acyl-CoA:cholesterol acyltransferase (184%), whereas ODS and progesterone reversed these compensatory responses in cholesterol-fed rats. Cholesterol 7 alpha-hydroxylase was changed no more than 22% by any treatment. A bolus of ODS elevated biliary cholesterol output 41% and shifted biliary bile acid synthesis and composition toward 12-deoxy bile acids. These effects were not seen in ODS-fed or progesterone-treated rats, in which cholesteryl ester stores were depleted. It is concluded that effects of free cholesterol on bile acid synthesis and biliary cholesterol are probably mediated by specific precursor or regulatory pools which can be independently regulated and which represent a relatively small fraction of hepatic free cholesterol.

Animals↗
PubMed1990

Hydrolysis of fluorescent pyrene-acyl esters by human pancreatic carboxylic ester hydrolase and bile salt-stimulated lipase.

Fluorescent esters containing pyrenedecanoic acid (P10) or pyrenebutanoic (P4) acid (P4cholesterol, P10cholesterol, P4- and P10-containing triacylglycerols) were synthesized and used as substrates for human pancreatic carboxylic ester hydrolase and bile salt-stimulated lipase from human milk. Both enzymes were purified by immunoaffinity chromatography. All fluorescent pyrene derivatives were hydrolyzed by pancreatic carboxylic ester hydrolase and bile salt-stimulated lipase, but at different rates. The hydrolytic rates of the "short" acyl esters (P4-containing esters) were higher than those of the "long" ones (P10-containing esters). Conditions were optimized for sensitivity of the assay using fluorescent cholesteryl esters. The pH optimum was 7.5-8.0. Sodium cholate exhibited a stronger activating effect than taurocholate or taurodeoxycholate (maximal activation was achieved with 5 mmol/L cholate and with a molar ratio cholesteryl ester/cholate around 1:10). Both pancreatic carboxylic ester hydrolase and bile salt-stimulated lipase from milk were strongly inhibited by the other amphiphiles tested, namely phosphatidylcholine and Triton X-100, and were inactivated by low concentrations (10 mumol/L) of the serine-reactive diethyl-paranitrophenyl phosphate (E600). Both enzymes were strongly inhibited by relatively low concentrations of plasma low density lipoproteins. These studies indicate that the fluorescent esters containing pyrene fatty acids can be used as substrates for assaying and investigating the properties of pancreatic carboxylic ester hydrolase as well as bile salt-stimulated lipase from milk.

Animals↗
PubMed1977

Reappraisal of cholesterol solubilization in bile salt-lecithin solution and the stability of bile.

On the basis obtained in a preceding study, cholesterol solubilization in aqueous bile salt-lecithin solution was investigated. The alteration of mixing sequence was found to yield differences not only in the rate but also in the magnitude of cholesterol solubilization. Both the rate and the magnitude were remarkably bigger in the system solubilizing cholesterol and lecithin mixture by bile salt than that solubilizing cholesterol crystal by bile salt with solubilized lecithin. A linear relation between the quantity of solubilized cholesterol and the concentration of bile salt except for lower concentration range was obtained for every bile salt-lecithin system. Values of k, the slope of the partial straight line, determined for cholate, chenodeoxycholate, deoxycholate and equimolar cholate-deoxycholate systems were 5.85 X 10(-2), 7.60 X 10(-2), 9.50 X 10(-2) and 7.17 X 10(-2), respectively. Cholesterol solubilizing power of bile salt was thus enhanced by the addition of lecithin. Since the solubilizing power could be given by the ratio of the solubilizate to the solubilizer, it was expressed graphically by the ratio of cholesterol to bile salt as ordinate and the concentration of bile salt as abscissa. The saturability of cholesterol solubilization in bile was purposefully exhibited in this graph by plotting assayed data of biliary lipid components.

Bile↗
PubMed1976

Basic studies on cholesterol solubilization in bile salt solution.

Previous studies on cholesterol solubilization by bile salts have often shown inconsistencies. To obtain basic informations on this problem, cholesterol solubilization in the aqueous solution of several bile salts have been reexamined. Kinetic studies revealed that not only the rate but also the magnitude of solubilization depended on the amount of excess cholesterol and the concentration of bile salt. An appropriate proportion of added cholesterol to bile salt was evaluated as 1:5-10 (w/w), corresponding to about 200% excess amount to approximate supposed solubility. The solubilization equilibrium was rather difficult to fix and must be checked by the procedure used. A linear relation was obtained between the quantity of solubilized cholesterol and the concentration of bile salt. The slope of the straight line was designated k. As the solubilizing power could be given by the ratio of the solubilizate to the solubilizer, it was expressed numerically by k value as well as graphically by the molar ratio of cholesterol to bile salt as ordinate and the molar concentration of bile salt as abscissa in which the above relation was hyperbolic, k being as asymptote. k values obtained for cholate, chenodeoxycholate, deoxycholate and equimolar cholate-deoxycholate mixture were 3.72 X 10(-2), 6.79 X 10(-2), 8.10 X 10(-2) and 6.55 X 10(-2) respectively.

Bile Acids and Salts↗
PubMed2003

Urinary excretion of bile acids in bile duct-ligated rats.

BACKGROUND: In patients with complete bile duct obstruction, the only pathway of bile acid elimination is through the urine. However, the urinary excretion of various bile acid conjugates in the presence of bile duct obstruction has not been clarified. Given this factor, the urinary excretion of various bile acids was compared in rats that were bile duct-ligated for 3 days. METHODS: After urinary bladder cannulation, radiolabeled bile acids were intravenously injected, and urine samples were collected every 2 h for 6 h, and radioactivity was counted. RESULTS: Urinary excretion (cumulative percent dose during 6 h) of taurocholate and cholate was similar (19.3% and 16.8%). Urinary excretion of tauroursodeoxycholate, lithocholate, and taurolithocholate-sulfate was less effective (12.7%, 9.8% and 2.1%, respectively). Cholate was mostly conjugated with taurine, and lithocholate was mostly conjugated with taurine and further hydroxylated. CONCLUSIONS: These results indicate that unconjugated bile acids were taken up by the liver and excreted into the blood after further biotransformation even under conditions of complete bile duct obstruction. Although bile acid sulfates are the major bile acids in the urine of patients with obstructive jaundice, monohydroxylated bile acids are considered not to be so effectively excreted into the urine, even with conjugation with taurine and sulfate, in rats.

Animals↗
PubMed2000

A scanning electron microscope study on the effects of different bile salts on the epithelial lining of jejunal mucosa.

Deconjugation of bile salts may occur in the jejunum under conditions of bacterial proliferation in the upper small intestine. We studied the morphological changes of jejunal mucosa induced by different conjugated (taurocholate, taurodeoxycholate, taurochenodeoxycholate, tauroursodeoxycholate) and unconjugated (cholate, deoxycholate, chenodeoxycholate, ursodeoxycholate) bile salts as compared by scanning electron microscopy. The epithelial lining of the jejunum was not affected in structural appearance below 40 mM concentration of the conjugated bile salts examined. On the other hand, the unconjugated bile salts examined induced morphological changes in varying degree and severity from crack formation at the tip to complete denudation of the jejunal villi, depending on the kind and dose of bile salts given. Among the unconjugated bile salts examined, the most robust in action was deoxycholate, which induced crack formation at 1.0 mM concentration, and the weakest was cholate. The study suggests that deconjugated bile salts produced by bacterial overgrowth in the upper small intestine can induce breakdown of the junctional integrity of the epithelial lining in varying degree and severity, ultimately leading to exfoliation of the epithelium.

Animals↗