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PubMed1992

Stimulatory and inhibitory effects of bile salts on rat pancreatic secretion.

The effects of various species of bile salts (chenodeoxycholate, deoxycholate, ursodeoxycholate and cholate, and their taurine and glycine conjugates) on pancreatic exocrine secretion were studied in conscious rats with external bile and pancreatic fistulae. For examination of the stimulatory effects of bile salts, bile and pancreatic juice were collected for a basal period of 90 minutes and returned to the intestine, and then solutions of bile salts (60 mmol/L) were infused intraduodenally at a rate of 1 mL/h for 2 hours. For examination of their inhibitory effects, pancreatic secretion was stimulated by exclusion of the bile and pancreatic juice; and then solutions of the bile salts were again infused intraduodenally. Chenodeoxycholate, glycochenodeoxycholate, ursodeoxycholate, deoxycholate, and its conjugates (glycodeoxycholate and taurodeoxycholate) significantly increased the fluid, bicarbonate and protein outputs, and bicarbonate concentration, with decrease in protein concentration. These increases were partially inhibited by infusion of either a cholecystokinin antagonist or secretin antibody. In contrast, cholate, taurocholate, tauroursodeoxycholate, glycoursodeoxycholate, and taurochenodeoxycholate inhibited pancreatic secretion and increase in the plasma cholecystokinin concentration produced by exclusion of bile and pancreatic juice. Thus, some bile salts, including taurocholate and taurochenodeoxycholate (major bile salts in rat bile) inhibited pancreatic secretion and cholecystokinin release, whereas some other bile salts increased pancreatic secretion via cholecystokinin release and secretin release.

Animals↗
PubMed1977

Hypocholesterolemic action of a novel delta8-dihydroabietamide derivative, THD-341, in rats.

The hypocholesterolemic properties of THD-341, N-(2,6-dimethylphenyl)-delta8-dihydroabietamide, were studied in rats. THD-341 reduced serum cholesterol levels in cholesterol-cholate-fed rats at a concentration of less than 0.001% in the diet or an oral dose of less than 3 mg/kg, once a day. When compared in terms of the 50% inhibitory dose for serum cholesterol elevation (ID 50%, % in diet), THD-341 (0.0008%) was comparable to D-thyroxine (0.0005%), more potent than estradiol (0.003%), and far more potent than clofibrate (0.2%), beta-sitosterol (0.8%), cholestyramine (2%), or nicotinic acid (3%). A daily intravenous injection of THD-341 was also effective (ID 50%: 7 mg/kg). THD-341 reduced serum and liver cholesterol in rats made hypercholesterolemic by 0.3% dietary thiouracil or 0.25% dietary cholate. Liver cholesteriol was more profoundly affected than the serum cholesterol. In normal rats, cholesterol was reduced in liver but not in serum. Its mechanism of action is unknown but the results suggest that THD-341 inhibits cholesterol absorption or re-absorption.

Abietanes↗
PubMed1979

Effect of feeding the shell fish (Corbicula japonica) on lipid metabolism in the rat.

Rats were maintained for 2 weeks on 3 different diets; a basal diet, one containing 0.1% cholate, and one containing 0.1% cholesterol and 0.1% cholate. Each dietary group was further divided into subgroups whose diet contained 0, 5 or 10% (dry weight) of minced corbicula (Corbicula japonica Prime). Feeding corbicula significantly reduced the increase of cholesterol levels in rats fed the cholesterol diet. Though corbicula contains several sterols, sterols other than cholesterol were almost not absorbed. Serum and liver triglyceride levels were significantly reduced by feeding corbicula meat in all the dietary groups. Activities of glucose-6-phosphate dehydrogenase, malic enzyme and acetyl-CoA carboxylase were also markedly reduced by feeding corbicula. The results suggest that corbicula is a hypolipidemic food.

Animal Feed↗
PubMed1985

Treatment of young rats with cholestyramine or a hypercholesterolemic diet does not influence the response of serum cholesterol to dietary cholesterol in later life.

Groups of 10 female Wistar rats (aged 4 weeks) were fed for 29 days either a low-cholesterol commercial diet, a commercial diet containing 2% (w/w) cholesterol, 0.5% cholate and 5% olive oil or a diet containing 2% cholestyramine. The rats were then fed the low-cholesterol commercial diet for the next 91 days and the high-cholesterol diet for another 29 days. There was no significant difference between the groups in the increase of cholesterol in serum and liver during the last period of cholesterol feeding. A fourth group of 10 animals was fed the diet containing cholesterol and cholate during the entire experimental period of 149 days. By the end of the experiment serum cholesterol in these animals was lower and liver cholesterol was higher than in the 3 groups fed the high-cholesterol diet during days 120-149 of the experiment. This study does not present evidence for imprinting effects of early diet manipulation on the later cholesterolemic response to a high cholesterol diet.

Age Factors↗
PubMed1994

Analysis of dansyl amino acids in feedstuffs and skin by micellar electrokinetic capillary chromatography.

Micellar electrokinetic capillary chromatography (MECC) using sodium dodecyl sulphate (SDS) and sodium cholate have been used for analyses of 30 dansylated (Dns) amino acids. The influences of sample preparation, Dns/amino acid ratio, sample solvent composition, and separation conditions including voltage, temperature, pH and buffer composition were investigated. Complete separations of acidic and neutral amino acids were obtained within 45 min in the SDS system. The efficiency expressed as number of theoretical plates for the applied capillary 0.52 m long were between 210,000 and 343,000, and the repeatability was very good with relative standard deviations on relative migration times between 0.09 and 0.70% and on relative normalised peak areas (RNPAs) between 0.85 and 3.41%. The linearity studies gave correlation coefficients between 0.9957 and 0.9993 for RNPAs against concentration. Detection limits were between 3 and 6 fmol or approximately 2 pg of each amino acid. Basic amino acids were separated in a MECC system using sodium cholate. Procedures and problems using Dns derivatisation for amino acids analysed by the MECC methods are described. Finally, examples of analyses of hydrolysates of real complex samples show, that this method can be applied to determine the amino acid composition of proteins in feedstuffs and skin.

Amino Acid Sequence↗
PubMed1983

Binding of phencyclidine to the detergent solubilized acetylcholine receptor from Torpedo marmorata.

The binding of phencyclidine to the acetylcholine receptor from Torpedo marmorata electroplaque was measured following solubilization of the receptor in sodium cholate followed by the exchange of cholate for Tween 80. In both the membrane-bound and solubilized AChR, the addition of cholinergic agonists simultaneously with the addition of PCP results in a 100 to 1000 fold increase in the PCP association rate and a 5 to 10 fold increase in the dissociation rate as compared to the unliganded AChR or AChR equilibrated with agonist prior to PCP addition. In addition, the number of binding sites and the pharmacological properties of the binding are not markedly changed in the soluble receptor. These results suggest that the acetylcholine receptor can undergo similar conformational transitions in the membrane-bound and the Tween 80 solubilized form and that phencyclidine can monitor these transitions in both cases.

Animals↗
PubMed1987

Reconstitution of the glucose transporter from rat skeletal muscle.

As a step in the purification and characterization of the glucose transporter from rat skeletal muscle, we have reconstituted glucose transport activity in liposomes. Plasma membranes were prepared from skeletal muscle which display D-glucose reversible binding of cytochalasin B (10 pmol sites/mg protein; KD = 0.3 microM). Older rats gave a slightly lower specific activity and much lower yield of sites per g muscle than young rats. Glucose transport activity was reconstituted into liposomes by the freeze-thaw procedure using either plasma membranes directly or cholate-extracted membrane proteins; the latter gave a 50% higher specific activity. The reconstituted transport activity was stereospecific, saturable, and inhibited by cytochalasin B, phloretin, and mercuric chloride. The optimum cholate concentration for extraction and reconstitution of transport activity was about 1.5%, and the highest specific activity of reconstituted transport was seen only at low ratios of protein to lipid in the reconstitution. Chromatography on agarose lentil lectin and agarose ethanethiol doubled both the specific activity of reconstituted transport and the fraction of glucose uptake which was stereospecific. In all of these respects the results were similar to our results with the bovine heart transporter (T. J. Wheeler and M. A. Hauck, Biochim. Biophys. Acta 818, 171-182 (1985)). Our findings suggest that further purification procedures developed for the heart transporter may be applicable to the skeletal muscle transporter as well.

Animals↗
PubMed1989

The deconjugation ability of bacteria isolated from the jejunal fluids in the blind loop syndrome with high 14CO2 excretion--using the breath analysis technique and thin-layer chromatography.

Five patients with blind loop syndrome (Billroth II) were examined by measuring 14CO2 specific activity of expired breath samples taken at intervals after a meal containing glycine-1-14C cholate. The 5 patients tested showed a marked increase of 14CO2 specific activity. Furthermore, the ability of deconjugation of bacteria isolated from the jejunal fluids in the efferent loop of these patients was tested by thin layer chromatography. The bacterial species identified from the samples were as follows: enterococcus, Lactobacillus (L) buchneri, L. bifidus, L. brevis, Eubacterium (E) lentum, Bacteroides (B) vulgaricus, B. filamentosum, Corynebacterium (C) granulosum, Escherichia (E) coli, Staphylococcus (S) epidermidis, and Aerobacter (A) aerogenes. These species of bacteria, except E. coli and A. aerogenes, showed the deconjugation ability by which conjugated bile acids in ox gall was hydrolyzed. Administration of chloramphenicol (1g per day for 14 days orally divided doses) to the 5 patients reduced 14CO2 specific activity significantly. On the other hand, 9 healthy men (control subjects) who were tested showed a flat curve, and 8 of the 9 had no growth of bacteria isolated from the jejunal fluids. The remaining healthy man showed an overgrowth of E. coli and Pseudomonas (P) aeruginosa, but the species did not have the ability of deconjugation. Thus, we concluded that the patients with blind loop syndrome(Billroth II) had the bacterial overgrowth in the efferent loop that contained species with deconjugation ability, and, as a result the bacterial overgrowth contributed to causing abnormalities (increased deconjugation) in the metabolism of bile acids in the small intestine. When the concentration of conjugated bile acids in the small intestine was reduced to levels below the critical micellar concentration by several factors, fat malabsorption and subsequent steatorrhea were induced (1,-4). Furthermore, H. Fromm and A. F. Hofmann presented in vivo that the patients with blind loop syndrome had fat malabsorption and the patients who had a high 14CO2 output after oral administration of glycine-1-14C cholate showed a low 14CO2 output after oral administration of antibiotic drug (5,6). However, there has been no report on the deconjugation ability of bile acids of bacteria isolated from the jejunal fluids in the efferent loop of patients with Billroth II who had positive breath tests.(ABSTRACT TRUNCATED AT 400 WORDS)

Bacteria↗
PubMed1989

Effects of oleic acid and bile salts on canine villous motility.

The effects on canine villous motility of mucosal Tyrodes solution containing oleic acid (10 mM) and/or either taurocholic or cholic acid (15 mM) in the presence or absence of IV atropine (1 mg/kg) was used to assess the neural mediation of the effects of luminal nutrients. Villous motility was measured over 12 min periods by in vivo videomicroscopy of segments of jejunum. Neither bile salt had effects alone but villous motility increased after oleic acid was added to taurocholate and decreased after oleic acid was added to cholate. Villous motility increased when taurocholate and oleic acid were present initially and returned to control levels when removed. Villous motility was not affected by cholate and oleic acid but villous motility decreased when they were removed from the Tyrodes solution. Atropine blocked the increase in villous motility caused by taurocholate and oleic acid. Bile salts can modify the effect of oleic acid on villous motility and a cholinergic step is involved in the stimulation of motility.

Animals↗
PubMed1990

The order of hepatic cytotoxicity of bile salts in vitro does not agree with that examined in vivo in rats.

Using an enzyme release from isolated rat hepatocytes incubated with a bile salt as a marker, the cytotoxic order of bile salts was found to be taurochenodeoxycholate, glycochenodeoxycholate greater than tauroursodeoxycholate, glycoursodeoxycholate, cholate greater than taurocholate, glycocholate. Thus, the cytotoxicity of conjugates of ursodeoxycholate was greater than that of conjugates of cholate. However, these data do not agree with the order of cytotoxicity of these bile salts previously studied in vivo by the authors which demonstrated the least cytotoxic nature of conjugates of ursodeoxycholate.

5'-Nucleotidase↗
PubMed1995

Bile salt secretion by hepatocytes incubated with bile salts and liposomes or low density lipoproteins.

The purpose of this work was to determine the effect of exogenous unesterified cholesterol provided in either artificial liposomes or LDL on bile salt synthesis by isolated rat hepatocytes. Rates of de novo synthesis were determined in the presence of 300 or 600 microM taurocholate, 600 microM taurodehydrocholate, cholate, deoxycholate or chenodeoxycholate. There was no significant difference between the cholesterol uptake by hepatocytes when the degree of hydrophobicity of the bile salts changed (cholate vs deoxycholate or chenodeoxycholate). Compared to taurocholate, taurodehydrocholate lowered the hepatic incorporation of unesterified cholesterol for the first 60 minutes; compared to control, taurocholate stimulated the cholesterol incorporation for the first 20 minutes. A possible explanation for this finding would be an interaction between bile salts and exogenous cholesterol, depending on the kind of conjugated bile salt. Taurocholate increased the exchange of cholesterol between liposomes or LDL and hepatocyte membranes. It resulted in a significant increase of bile salt synthesis and secretion. This phenomenon was not observed with taurodehydrocholate.

Animals↗
PubMed1978

Effect of pH on bile salt degradation by mixed fecal cultures.

Stoll specimens from 3 healthy volunteers were cultured under an-aerobic conditions in brain heart infusion broth with and without the addition of cholate, deoxycholate of chenodeoxycholate. The initial pH of the medium was adjusted to 5.5, 6.3, 7.3 (unadjusted), 8.0, and 9.0. Cell-free extracts prepared from the resulting bacterial growth contained increased levels of NAD- and NADP-dependent 3alpha-, 7alpha-, and 12alpha-hydroxysteroid oxidoreductases when the initial pH was 8.0 or 9.0 and depressed levels of these activities when the initial pH was 5.5 or 6.3 (as compared to control values obtained at 7.3). At pH 5,5 all activities except NAD-dependent 7alpha-hydroxysteroid oxidoreductase were absent. A powerful selective effect was imposed on NAD-dependent 7alpha-hydroxysteroid oxidoreductase when deoxycholate or chenodeoxycholate were incorporated into or chenodeoxycholate were incorporated into the medium. Thin-layer chromatography of either extracts of cholate-containing, acidified spent bacterial medium showed alkaline or neutral (optimal at pH 8). The precent hydroxyl group estimations at the 3alpha-, 7alpha-, and 12alpha-positions revealed an increase in disappearance of OH groups at all three positions with increasing initial pH value. The order of extent of bioconversion was 7alpha-OH greater than 3alpha-OH; at pH 8 AND 9, approximately 90% 7alpha-OH bioconversion was observed. Spent bacterial media and a number of commercial secondary bile salts were all negative in the Ames' assay for mutagenicity.

Anaerobiosis↗
PubMed1987

Arachidonic acid transfer from diacyl-sn-glycero-3-phosphocholine to ether phospholipids in rat peripheral blood lymphocytes.

The main phospholipid fractions of rat peripheral blood lymphocytes consisted of 30.8% diacylglycerophosphocholine and 20.3% diacylglycerophosphoethanolamine; the proportion of the ether phospholipids were small especially of alkyl- and alkenyl-glycerophosphoethanolamine (3.3 and 6.6% respectively). Other classes of phospholipids included glycerophosphoserine (10.5%), glycerophosphoinositol (6.5%) and sphingomyelin (13.6%). The incorporation of labeled arachidonic acid in the glycerophospholipids showed a rapid uptake into diacyl and ether classes of phospholipids and into triglycerides. When labeled cells were reincubated without arachidonic acid the diacylglycerophosphocholine rapidly lost its radioactivity, but a concomitant increase was observed in alkylacylglycerophosphocholine and more especially in alkenylacylglycerophosphoethanolamine and a smaller increase in alkyl- and diacyl-glycerophosphoethanolamine. The radioactivity was fairly constant in glycerophosphoserine and in glycerophosphoinositol, but decreased slightly in triglycerides. The arachidonic acid transfer reaction was completed after 2-3 hours reincubation. When labeled cells were reincubated in the presence of sodium cholate, the loss of radioactivity in the diacylglycerophosphocholine fraction increased. The transfer of arachidonic acid to ether phospholipids was the same with or without sodium cholate, but the later enhanced arachidonic acid transfer to diacylglycerophosphoethanolamine.

Animals↗
PubMed1996

Influence of bile salts on hepatic mdr2 P-glycoprotein expression.

Mdr2 P-glycoprotein is expressed in the canalicular membrane of the mouse hepatocyte and is responsible for phospholipid secretion into bile. It is our hypothesis that it functions as a flippase in the translocation of phosphatidylcholine from the inner leaflet to the outer leaflet of the canalicular membrane. We have investigated the influence of different types of bile salts on the expression levels of mdr2 Pgp. Feeding mice a cholate-supplemented diet results in an increased mdr2 mRNA level, and this is accompanied by an increased biliary phospholipid secretion capacity. Cholate is a more hydrophobic bile salt than the main endogenous bile salt, muricholate. The induction of mdr2 gene expression and concomitant increase in phospholipid secretion are in line with the function of biliary phospholipids to inactivate the detergent action of hydrophobic bile salts.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1990

Characterizing mechanisms of hepatic bile acid transport utilizing isolated membrane vesicles.

Utilizing the above-outlined approaches, mechanisms of hepatic bile acid transport have been characterized in membrane vesicles of rat liver, particularly for the conjugated trihydroxy bile acid, taurocholic acid. Uptake across the sinusoidal membrane is carrier mediated and coupled to the transmembrane sodium gradient. This carrier has an apparent Km between 30 to 50 microM and a Vmax between 4 to 6 nmol mg-1 protein min-1. Furthermore, Na+ gradient-dependent sinusoidal uptake of taurocholate can be stimulated by low concentrations of albumin. There is controversy as to whether the process is electrogenic. Although photoaffinity labeling studies indicate that an additional carrier for Na(+)-dependent bile acid uptake is also present at the sinusoidal membrane, this carrier has so far not been characterized in membrane vesicles. The proposition that pH gradient-driven furosemide-sensitive cholic acid uptake into sinusoidal membrane vesicles may represent carrier-mediated hydroxyl/cholate exchange must be revised on the basis of the recent findings that (1) true initial uptake rates are not saturable; (2) pH gradient-driven cholate uptake is also found in liposomes; and (3) furosemide also inhibits pH gradient-driven cholate uptake in liposomes. The mechanisms of transcellular transport of bile acids have been studied less extensively, but Na(+)-independent carrier-mediated taurocholic acid transport has been demonstrated in purified subcellular fractions such as rat liver microsomes and Golgi membranes. Finally, transport studies in canalicular rat liver plasma membrane vesicles indicate that canalicular excretion of bile acids is also a carrier-mediated process that may be driven, at least in part, by the physiologic electrical potential gradient, and that preferentially transports trihydroxy and conjugated dihydroxy bile acids.

Animals↗
PubMedDate not supplied

Irreversible labelling of delta-opioid receptors in rat brain and neuroblastoma cells by [3H]azido-DTLET: characterization of subunits and autoradiographic visualization of the covalent binding.

[3H]Az-DTLET (Tyr-D-Thr-Gly-Phe(pN3)-Leu-Thr), a photoaffinity probe for delta opioid receptors binds to a single class of sites in rat brain membranes with a high affinity (KD = 1.66 nM). The selectivity index of Az-DTLET (KI delta/KI mu = 0.036) is better than that of its precursor DTLET (0.053). Rat brain or neuroblastoma glioma cells membranes were incubated with 10 nM [3H]Az-DTLET, washed and irradiated with U.V. After irradiation a fraction (20-30%) of specific binding was found to remain indissociable after 10 min at 60 degrees C and was considered as irreversible. This fraction increased as a function of the irradiation time. The radioactivity irreversibly bound to rat brain membranes, solubilized by sodium cholate, was associated with high molecular weight species (200,000 daltons). In denaturing conditions (SDS 2%), the [3H]Az-DTLET specific binding was associated with molecular components of 45-50 K and 90-100 K daltons. In contrast, when opioid receptors were prelabelled by [3H]Az-DTLET, solubilized by Na-cholate and irradiated, the radioactivity was only recovered with subunits of 45-50 K daltons. The autoradiographic localization of the irreversibly bound [3H]Az-DTLET in rat brain was identical to that of reversibly bound [3H]DTLET or [3H]Az-DTLET. These results suggest that [3H]Az-DTLET represents an adequate specific probe for studies on the structure, function and anatomical distribution at light and even electron microscopic level of delta-opioid receptors.

Animals↗
PubMed1983

Properties of detergent-dispersed iodothyronine 5- and 5'-deiodinase activities from rat liver.

In order to obtain more knowledge about the regulation and mechanism of thyroid hormone deiodination, some properties of detergent-solubilized iodothyronine deiodinase have been studied. Moreover, a starting point for its purification has been made. Several chromatography media were tested for their ability to purify the deiodinases. In some instances, a 4-fold purification was obtained. Treatment of cholate-solubilized microsomes with 35% ammonium sulphate resulted in quantitative precipitation of the deiodinase activities and concomitant removal of phospholipid. The pellet could be solubilized with 0.3% W-1 ether and the deiodinase in this ammonium sulphate extract exhibited approximately 10-fold higher apparent Km and Vmax values for its substrate compared with the cholate extract. Readdition of some phospholipids was shown to decrease enzyme activity. Isoelectric focusing of W-1 ether-solubilized microsomes resulted in a major activity peak around pH 6.4 and a minor peak at pH 5.2, while in the ammonium sulphate extract the deiodinase had an isoelectric point at pH 9.3. Refocusing of this activity peak yielded a preparation with a specific activity only 3-times higher than in the ammonium sulphate extract. However, after sodium dodecyl sulphate polyacrylamide gel electrophoresis only five bands could be detected. The elevated kinetic parameters as well as the higher isoelectric point of the deiodinase after ammonium sulphate treatment were caused by delipidation of the enzyme. Both the change in isoelectric point and the behaviour on several column materials were found to be similar for the 5- and 5'-deiodinase activities. These results suggest that a single enzyme is operative in the deiodination of iodothyronines in rat liver and that its activity may be regulated by phospholipids.

Animals↗
PubMed1987

Characterization of the aflatoxin B1-binding site of rat albumin.

A fluorescence-enhancement method was used to investigate the non-covalent interaction between aflatoxin B1 and rat albumin. Solvent-induced shifts in the emission spectrum of aflatoxin B1 provided evidence that the aflatoxin B1-binding site of rat albumin is a highly nonpolar environment. A dissociation constant of 20 microM was determined at 20 degrees C. The possibility that aflatoxin B1 binds one of the three major drug sites of albumin was investigated by ligand-displacement experiments. Mechanisms whereby marker ligands displace aflatoxin B1 were further investigated by comparing the experimental binding parameters with those derived theoretically, assuming competitive binding. The results indicate that: aflatoxin B1 and phenylbutazone compete for a common high-affinity site on rat albumin; high-affinity binding of aflatoxin B1 and site-II marker ligands takes place independently; aflatoxin B1 does not compete with either cholate or warfarin for the same high-affinity site, but the simultaneous binding of warfarin or cholate negatively modulates the binding of aflatoxin B1 to albumin. Fluorescence energy-transfer studies show that the lone tryptophan residue, Trp-214, is not associated with the aflatoxin B1-binding site.

Aflatoxin B1↗