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PubMed1987

Metabolism of 5-fluorouracil to an N-cholyl-2-fluoro-beta-alanine conjugate: previously unrecognized role for bile acids in drug conjugation.

Recently we demonstrated clinically significant levels of a previously unrecognized metabolite of the anticancer drug 5-fluorouracil (FUra) in bile of cancer patients. In the present study, reanalysis of bile from these patients demonstrated the presence of not one but two previously unrecognized metabolites. The major unrecognized metabolite was purified by reversed-phase HPLC, after which its molecular weight was determined by fast-atom-bombardment mass spectrometry to be 497. The similarity in HPLC retention times and molecular weights of this FUra derivative and the bile acids N-cholylglycine (Mr 465) and N-cholyltaurine (Mr 515), along with the structural similarity of the FUra catabolite 2-fluoro-beta-alanine and the amino acids glycine and taurine, led to the hypothesis that this metabolite could be a conjugate of 2-fluoro-beta-alanine and cholic acid. This hypothesis was tested and confirmed by hydrolyzing the purified metabolite by cholylglycine hydrolase after which: 2-fluoro-beta-alanine was demonstrated by using a sensitive HPLC technique capable of resolving all of the known putative FUra metabolites, and unconjugated cholic acid was identified by both GC and GC-MS. Additionally, chemically synthesized N-cholyl-2-fluoro-beta-alanine was shown to cochromatograph on HPLC and TLC with the purified biliary metabolite. In summary, this study demonstrates a unique, so far as we know, pathway of drug metabolism in man in which an amino acid drug metabolite is conjugated with cholic acid and eliminated into the bile. Furthermore, the finding that 2-fluoro-beta-alanine is conjugated to bile acids may provide some insight into the mechanism of cholestasis that is frequently observed after administration of fluoropyrimidine by hepatic arterial infusion.

Alanine↗

PubMed1984

[Increase of bile acid reabsorption following total small intestine resection in the rat].

Bile salts undergo an enterohepatic circulation. The relative distribution of labelled cholic acid in portal blood, enterocytes, intestinal contents and feces, following intravenous injection of (carboxylic-14C) cholic acid, can be considered as an indication of the absorptive capacity of the epithelium cells. Seven days after a massive small intestinal resection (60-80 cm), the animal weight and the bile salt absorption were significantly decreased. Nevertheless, thirty days after the operation, weight and radioactivities reached the values found in the controls: in portal and cava blood, liver, intestinal contents and feces. An increase of the absorptive capacity of the intestinal epithelial cells was also observed.

Animals↗

PubMed1984

The economy of the enterohepatic circulation of bile acids in the baboon. 2. Regulation of bile acid synthesis by enterohepatic circulation of bile acids.

Isotope dilution within bile acid pools and radiochemical assessment of cholesterol oxidation to bile acids were methods used to measure short-term feedback regulation of bile acid synthesis in baboons with controlled enterohepatic circulations. Intraduodenal infusion of labeled endogenous bile acid pools into bile acid-depleted animals with enhanced bile acid synthesis showed that the rate of bile acid returned to the liver affected the degree of inhibition of bile acid synthesis. Infusion of prepared bile acid pools of varying composition resulted in a specific pattern of feedback inhibition of bile salt synthesis related to pool composition and mass. Individual bile salts inhibited their own synthesis more than that of other bile salts, and chenodeoxycholic and deoxycholic acids were found to have greater inhibitory effects than cholic acid. Glycine-conjugated cholic and chenodeoxycholic acids had greater inhibitory effects than did the respective free bile salts. Infusion of mixed bile acid pools showed that dihydroxy bile acids (chenodeoxycholic or deoxycholic) enhanced feedback inhibition of cholic acid. In all studies, inhibition of bile acid synthesis occurred twice as fast as its derepression.

Animals↗

PubMed1976

Identification and characterization of a bile acid receptor in isolated liver surface membranes.

It is generally assumed that hepatic transport of bile acids is a carrier-mediated process. However, the basic mechanisms by which these organic anions are translocated across the liver cell surface membrane are not well understood. Since carrier-mediated transport involved binding of the transported molecule to specific receptor sites, we have investigated the possibility that bile acid receptors are present in liver surface membranes. Isolated liver surface membranes were incubated at 4 degrees C with [14C]cholic acid and [14C]taurocholic acid, and membrane-boudn bile acid was separated from free by a rapid ultrafiltration technique through glass-fiber filters. Specific bile acid binding is rapid and reversible and represents approximately 80% of the total bile acid bound to liver surface membranes. Taurocholic acid binding is independent of the medium pH, while cholic acid binding demonstrates an optimum at pH 6.0. Analysis of equilibrium data for both cholic and taurocholic acid binding indicates that specific binding is saturable and consistent with Michaelis-Menten kinetics, while nonspecific binding is nonsaturable. Apparent maximal binding capacity and dissociation constant values indicate a large capacity system of receptors that have an affinity for bile acids comparable to that of the hepatic transport mechanism. Scatchard analysis of the saturation kinetics as well as inhibition studies suggest that bile acids bind to a single and noninteracting class of anion that competes with bile acids for hepatic uptake, also inhibits cholic acid binding. In contrast, no inhibition was demonstrated with indocyanine green and probenecid. Specific bile acid binding is enriched and primarily located in liver surface membranes and found only in tissues involved in bile acid transport. Specific bile acid binding is independnet of Na+, Ca2+, and Mg2+ and does not require metabolic energy. In addition, thiol groups and disulfide are not required for activity at the binding site. However, specific bile acid binding is markedly decreased by low concentrations of proteolytic enzymes and is also decreased by the action of neuraminidase and phospholipases A and C. These results are consistent with the existence of a homogeneous bile acid receptor protein in liver surface membranes. The primary surface membrane location of this receptor, its binding properties, and its ligand specificity suggest that bile acid binding to this receptor may represent the initial interaction in bile acid transport across liver surface membranes.

Adenosine Triphosphatases↗

PubMed1976

Bile acid metabolism after jejunoileal bypass operation for obesity.

Bile acid metabolism and duodenal bacterial flora were studied in 12 obese patients before and 1-2 months after jejunoileal bypass operation, either including 37.5 cm jejunum and 12.5 cm ileum (Type I) or 12.5 cm jejunum and 37.5 cm ileum (Type III). The cholic acid pool size was unchanged after type I, but decreased after type III, bypass. The daily fractional turn-over of cholic acid increased about five times after both types of operation. The synthesis rate of cholic acid increased after both types of bypass, but more after type I than after type III. In duodenal bile the ratios of cholic to taurine conjugates increased after type I, but were unchanged after type III bypass, whereas the ratio of cholic to chenodeoxycholic acid was unchanged after both types of bypass. The bacterial flora and the occurrence of free bile acids in the fasting duodenal contents did not change after either of the two types of bypass operation. It is concluded that jejunoileal bypass results in marked disturbances in the bile acid metabolism. Surprisingly, these are most severe after bypass including the longest ileum, possibly because of insufficient stimulation of the bile acid synthesis in this type of operation.

Bile Acids and Salts↗

PubMed1985

The effect of calcium on the pathogenicity of high fat diets to the colon.

The pathogenicity of lipid components and dietary fats on the colonic epithelium have been studied with five model systems in experimental animals, with rectal perfusion of bile acids, colonic perfusion of bile acid solutions, dietary supplementation with cholic acid, oral boluses of fat, and diets with various levels of fats. The lipid or fat led to colonic epithelial cell cytotoxicity and/or an increase in cell proliferation which was inhibited by supplementary calcium. These results could mean that calcium may reduce the toxicity of high fat diets to the colon and reduce the colonic cancer risk associated with high fat diets.

Animals↗

PubMed1999

Influence of various bile acids on the metabolism of glycyrrhizin and glycyrrhetic acid by Ruminococcus sp. PO1-3 of human intestinal bacteria.

Ruminococcus sp. PO1-3, an intestinal bacterium isolated from human feces, metabolized glycyrrhizin (GL) to glycyrrhetic acid (GA) and GA to 3-oxo-glycyrrhetic acid (3-oxo-GA) and possessed GL beta-D-glucuronidase and 3beta-hydroxysteroid dehydrogenase (3beta-HSD) involved in the metabolism of GL. This bacterial growth was enhanced by GL at a concentration of 0.4 mm and was suppressed by GA at concentration of 1.0 mM. Chenodeoxycholic acid, deoxycholic acid and lithocholic acid among the bile acids added to this bacterium suppressed the growth and GL beta-D-glucuronidase activity and 3beta-HSD activity incident to it at a concentration of 1.0 mM, while cholic acid, hyodeoxycholic acid and glycine and taurin conjugates of cholic acid, chenodeoxycholic acid, deoxycholic acid and lithocholic acid had almost no effect on this bacterium at a concentration of 0.2 to 1.0 mm. However, these enzyme activities of this sonicated bacteria were inhibited by all of these bile acids. Although each bile acid and GL added to bacteria at the same time suppressed the growth and the amount of metabolite GA by all bile acids used except cholic acid, taurocholic acid and taurodeoxycholic acid with GL, a combination of each bile acid and GA eased the growth inhibition caused by GA at a concentration of 0.2 mM and enhanced the amount of metabolite 3-oxo-GA by the glycine conjugate of bile acids with GA. GL or GA added after 6 h culture with each of these bile acids and bacteria was metabolized to a relatively large amount of GA by chenodeoxycholic acid and lithocholic acid and their glycine and taurine conjugates, glycocholic acid and taurodeoxycholic acid, or had almost no effect on the amount of metabolite 3-oxo-GA, respectively. These results showed that although GL added after the exposure to bile acid and GA and bile acid added at the same time as bacteria had different bile acid action, these conditions enhanced the amount of metabolite GA from GL and metabolite 3-oxo-GA from GA.

Bacteria, Anaerobic↗

PubMed1974

Increased formation of ursodeoxycholic acid in patients treated with chenodeoxycholic acid.

The formation of ursodeoxycholic acid, the 7 beta-hydroxy epimer of chenodeoxycholic acid, was investigated in three subjects with cerebrotendinous xanthomatosis and in four subjects with gallstones. Total biliary bile acid composition was analyzed by gas-liquid chromatography before and after 4 months of treatment with 0.75 g/day of chenodeoxycholic acid. Individual bile acids were identified by mass spectrometry. Before treatment, bile from cerebrotendinous xanthomatosis (CTX) subjects contained cholic acid, 85%; chenodeoxycholic acid, 7%; deoxycholic acid, 3%; allocholic acid, 3%; and unidentified steroids, 2%; while bile from gallstone subjects contained cholic acid, 45%; chenodeoxycholic acid, 43%; deoxycholic acid, 11%, and lithocholic acid, 1%. In all subjects, 4 months of chenodeoxycholic acid therapy increased the proportion of this bile acid to approximately 80% and decreased cholic acid to 3% of the total biliary bile acids, the remaining 17% of bile acids were identified as ursodeoxycholic acid. After the intravenous injection of [3H]chenodeoxycholic acid, the specific activity of biliary ursodeoxycholic acid exceeded the specific activity of chenodeoxycholic acid, and the resulting specific activity decay curves suggested precursor-product relationships. When [3H]7-ketolithocholic acid was administrated to another patient treated with chenodeoxycholic acid, radioactivity was detected in both the ursodeoxycholic acid and chenodeoxycholic acid fractions. These results indicate that substantial amounts of ursodeoxycholic acid are formed in patients treated with chenodeoxycholic acid. The ursodeoxycholic acid was synthesized from chenodeoxycholic acid presumably via 7-ketolithocholic acid.

Bile Acids and Salts↗

PubMed1977

[Effect of various dietary carbohydrates on supplementary cholesterol].

The effect of addition of different carbohydrates (starch, glucose, fructose) to the feed was investigated using the experimental animal. Additionally, the admixture of cholesterol and of cholesterol plus cholic acid was tested. Fructose (70% of the feed) causes a slight increase in serum triglyceride concentration and a very slight increase in triglyceride concentration in the liver. Fructose and to a lesser degree glucose cause an increase in pyruvate kinase activity in the liver. The activity of glucose-6-phosphate dehydrogenase is increased slightly following high-dosed glucose, whereas the increase is very pronounced following fuctose-rich feed. The admixture of cholesterol (with cholic acid) causes a decrease in glucose-6-phosphate dehydrogenase activity up to 70%. The activity of glutamate dehydrogenase is decreased also following cholesterol admixture. A fructose-rich diet causes a slight degree of hyperlipemia with a metabolic situation similar to a latent diabetic state. This effect is greatly intensified by the addition of cholesterol and cholic acid to the diet of the rats. Especially striking was the increase in serum-free-fatty-acid concentrations in all groups of animals. This is speculated to be a sign of insulin deficiency. The so-called "carbohydrate-induced hypertriglyceridemia" is obviously intensified within a short period by the admixture of cholesterol plus cholic acid to the experimental diet.

Animals↗

PubMed1987

Quantitation of serum bile acids by isotope dilution with 13C-labelled homologs.

Quantitation of individual bile acids in serum can be carried out with radioimmunoassays or with gas chromatography. The most specific measurements are obtained with combined gas chromatography/mass spectrometry employing stable isotope labelled bile acids as internal standards. So far only the use of deuterated internal standards has been described for this purpose. 24-13C-labelled bile acids have not been used since correction for the natural abundance of the 13C contribution has to be made. Furthermore, the maximal degree of labelling of 13C-labelled bile acids is about 90%. This requires additional correction for the percentage of unlabelled molecules. Using 13C-labelled bile acids as internal standards and adequate corrections for isotope interferences we have measured individual serum bile acids in healthy volunteers by inverse isotope dilution with coefficient of variation (CV) values of 5.4-6.2% determined for the total procedure of sample preparation and analytical technique. In fasting serum of 15 healthy volunteers chenodeoxycholic acid averaged 0.98 +/- SD 0.77 mumol/l, cholic acid 0.49 +/- 0.39 mumol/l and deoxycholic acid 1.07 +/- 0.68 mumol/l. Two hours postprandially these values increased to 2.42 +/- 1.46 mumol/l for chenodeoxycholic acid, 0.81 +/- 0.45 mumol/l for cholic acid and 1.66 +/- 1.02 mumol/l for deoxycholic acid. These data agree well with those described in the literature obtained with deuterated internal standards. It may be concluded that 24-13C-labelled bile acids are suitable as internal standards for quantitation of serum bile acids, if corrections for isotope interferences are made.

Adult↗

PubMed1988

The in vitro porcine brain tubulin assembly assay: effects of a genotoxic carcinogen (aflatoxin B1), eight tumor promoters and nine miscellaneous substances.

Aflatoxin B1 (AFB1) had a reversible inhibitory effect on the assembly of porcine brain tubulin in vitro. The 30%-inhibition concentration was 0.3 mM AFB1. The 8 tumor promoters showed different effects. Five of them, anthralin, cholic acid, gamma-hexachlorocyclohexane (lindane, gamma-HCH), lithocholic acid and phenobarbital (PB), enhanced the in vitro assembly. The effect was reversible in the case of PB and anthralin, only partially reversible in the case of cholic acid and gamma-HCH, whereas the stimulating effects of lithocholic acid led to an irreversible modification of the tubulin structure, as shown by the insolubility of the microtubules at 0 degrees C. This could be confirmed by an electron microscopic study. The doses necessary for a 30% enhancement of the steady-state level were 3 mM (PB), 0.2 mM (anthralin), 6 mM (cholic acid), 0.7 mM (gamma-HCH) and less than 0.2 mM (lithocholic acid). The other 3 tumor promoters tested - diethylstilbestrol (DES), 4,4'-dichloro-diphenyl-trichloro-ethane (DDT) and saccharin - inhibited the assembly. The concentrations necessary for a 30% inhibition varied within a wide range: 0.025 mM, 0.4 mM and 7.5 mM for DES, DDT and saccharin, respectively. Five of the 9 miscellaneous compounds, namely asbestos (crocidolite), bavistan, colchicine, chloropropham and ethylacetate, showed inhibitory effects, whereas Fe2+ (a constituent of asbestos) and 5-azacytidine did not influence the assembly process. The 30%-inhibition concentrations for colchicine, ethylacetate and asbestos were 10 microM, 0.153 M and 0.19 mM, respectively. For bavistan and chloropropham the 30%-inhibition values were 0.7 mM and 2.0 mM, respectively. The inhibitory effects of chloropropham and asbestos were reversible. For colchicine and bavistan the reversibility of the effects was not assayed. In agreement with published data, dimethylsulfoxide (DMSO) and acetone enhanced the in vitro assembly of porcine brain tubulin. The doses needed for a 30% enhancement by DMSO and acetone were 0.4 mM and 0.136 M, respectively. The effect of DMSO was irreversible whereas acetone led to a reversible stimulation. Some compounds were tested for their influence on preformed microtubules (interaction with the equilibrium between assembly and disassembly). Anthralin, cholic acid, PB and DMSO showed no effect on the steady-state plateau. A slight reduction was induced by DDT and bavistan, whereas DES, colchicine and chloropropham led to a pronounced reduction.

Aflatoxins↗

PubMed1981

Isolation and characterization of thirteen intestinal microorganisms capable of 7 alpha-dehydroxylating bile acids.

Thirteen anaerobic bacteria capable of performing the 7 alpha-dehydroxylation of both cholic acid and chenodeoxycholic acid were isolated from human feces and also from sewage. Ten organisms from heat-treated samples were species of Clostridium identical or closely related to the Clostridium bifermentans-C. sordellii group and consisted of four strains elaborating 7 alpha-dehydroxylase alone and six strains capable of catalyzing both 7 alpha-dehydrogenation and 7 alpha-dehydroxylation. The remaining three organisms, recovered from fresh human feces, were gram-positive, nonflagellated, nonsporeforming, anaerobic rods and comprised two distinct species. Strain HD-17, still unidentified, had both activities, but was unique in that it exclusively 7 alpha-dehydroxylated cholic acid while biotransforming chenodeoxycholic acid, preferably though 7 alpha-dehydrogenation. Two unclassified strains, b-8 and c-25, metabolized both acids though 7 alpha-dehydroxylation and 7 alpha-dehydrogenation. Except for strains b-8 and c-25, all of th 7 alpha-dehydroxylating bacteria split the conjugated bile acid series, and hydrolases were detected in cell-free filtrates of early stationary-phase broth cultures.

Bacteria↗

PubMed1982

Effect of 7-ketolithocholic acid on bile acid metabolism in humans.

The effect of 7-ketolithocholic acid on biliary bile acid composition, cholesterol saturation, and as an intermediate in the conversion of chenodeoxycholic acid to ursodeoxycholic acid was investigated in 5 subjects with gallstones. After 7-ketolithocholic acid (400 mg/day) was administered orally for 14 days, biliary bile acid composition changed: The proportion of cholic acid decreased (from 45% to 19%), deoxycholic acid decreased (from 15% to 10%), chenodeoxycholic acid increased markedly (from 36% to 59%), ursodeoxycholic acid increased (from 36% to 59%), ursodeoxycholic acid increased (from 2% to 7%), and lithocholic acid increased (from 2% to 5%), while only trace amounts of 7-ketolithocholic acid were detected. During this treatment, the biliary lithogenic index fell from 2.6 to 0.9 and was accompanied by a pronounced drop in biliary cholesterol concentration. After biliary bile acid levels became constant [24-14C]chenodeoxycholic acid was given intravenously as a pulse-label, and the resultant biliary ursodeoxycholic acid and lithocholic acid specific activity curves showed a precursor--product relationship with chenodeoxycholic acid. Similarly, when uniformly labeled 7-[24-14C]ketolithocholic acid was fed (400 mg/day, 1000 +/- 100 dpm/mg) the specific activities of biliary chenodeoxycholic acid and ursodeoxycholic acid became constant and approximated each other, but these were only 75% as high as the fed 7-ketolithocholic acid. These results indicate that 7-ketolithocholic acid is absorbed, and suppresses endogenous bile acid production and biliary cholesterol secretion. Both isotopic experiments infer that ursodeoxycholic acid and lithocholic acid are formed from chenodeoxycholic acid and not from 7-ketolithocholic acid. The reduction in biliary lithogenic index and in cholesterol concentration suggest that low doses of 7-ketolithocholic acid may be effective in dissolving gallstones.

Bile↗

PubMed1984

Changes in biliary and fecal bile acids in mice after treatments with diosgenin and beta-sitosterol.

Diosgenin and beta-sitosterol (1% in diet) were administered to CRJ:CD-1 male mice for 15 days, in order to examine the changes in bile acid metabolism. There were some differences between diosgenin and beta-sitosterol in their effects on diet intake, liver weight, and plasma cholesterol level. However, both phytosterols caused no statistically significant changes in body weight gain, decreased cholesterol absorption to about one-third that observed in control mice, decreased liver cholesterol level, increased fecal excretion of cholesterol, and decreased fecal excretion of bile acids. Most of the increase in fecal excretion of cholesterol occurred 2 days after the start of feeding of phytosterols and gradually declined thereafter, but the levels on day 15 were nevertheless higher than those in the control mice. The fecal excretion of bile acids decreased progressively after the treatment with phytosterols. The decrease of bile acid derived from chenodeoxycholic acid was more predominant than the decrease of those derived from cholic acid, resulting in an increase of the cholic acid/chenodeoxycholic acid ratio. The biliary cholesterol, phospholipid, and bile acid mole % ratios and the lithogenic index were not changed, but the percentages of cholic acid and its related bile acids (the cholic acid group) to the total bile acids increased and those of the chenodeoxycholic acid group decreased after the treatments. The pool size of bile acids decreased in the mice given diosgenin but not in those given beta-sitosterol. Distribution of bile acids between the gallbladder and intestine was not altered by either phytosterol.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

The effect of oral absorption enhancers on the in vivo performance of insulin-loaded poly(ethylcyanoacrylate) nanospheres in diabetic rats.

Poly(ethylcyanoacrylate) (PECA) nanospheres have been employed as biodegradable polymeric carriers for oral (po) delivery of insulin. The main goal of this investigation was to screen various absorption enhancers, which were used to protect insulin-loaded PECA, by following their in vivo performance after oral administrations to streptozotocin-induced diabetic rats. The nanospheres were prepared by polymerization in a continuous aqueous phase at pH 2.5 and in the presence of Pluronic 68 (0.5%). This polymerization technique was able to hold 85 +/- 7.5% of insulin added, 30 min after initiation of polymerization. The drug loading was evaluated by HPLC. Insulin absorption after oral administration was evaluated by its hypoglycemic effect. The addition of protease inhibitor to insulin-loaded PECA nanospheres significantly reduced the blood glucose level after po administrations. Capric acid (0.5%) showed the maximum reduction in blood glucose level (bG max = 34.4 +/- 4.1 mg%), while cholic acid (0.5%) showed the fastest reduction in blood glucose level (Tmax, G = 6.0 +/- 0.2 h) among the tested oral absorption enhancers. Insulin associated with PECA nanospheres retained its biological activity up to 12 days in 50% of the rats in the presence of glycyrrhizic acid (1%). The per cent pharmacological availabilities (PA%) were in the order of capric acid (0.5%) > glycyrrhizic acid (1%) > deoxycholic acid (0.5%) > hydroxypropyl-beta-cyclodextrin (HPbetaCD) (1%) > cholic acid (0.5%). There was no significant difference in the PA% between capric acid (0.5%), glycyrrhizic acid (1%) and deoxycholic acid (0.5%). Although sodium cholate (0.5%) showed the lowest increase in PA% (3.1 +/- 3.11%), its Tmax G was the shortest (6 +/- 0.2 h) among the tested absorption enhancers. The reduction in blood glucose levels was maintained < 200 mg/dL in the order of glycyrrhizic acid (166 +/- 56 h) > capric acid (72 h) >; deoxycholic acid (66 +/- 6 h) > no enhancer (64 +/- 16 h) > HPbetaCI) (31 +/- 17.5) > cholic acid (22 +/- 5.7 h) > aprotenin (20 +/- 3.5 h). Therefore, capric acid and glycyrrhizic acid could be successfully used as oral absorption enhancers.

Administration, Oral↗

PubMed2003

Bile acids increase response and expression of human myometrial oxytocin receptor.

OBJECTIVE: We tested the hypothesis that during intrahepatic cholestasis of pregnancy bile acids activate the myometrial oxytocin receptor pathway. STUDY DESIGN: Myometrial sensitivity to oxytocin and oxytocin-receptor messenger RNA and protein level was investigated. The ability of cholic acid to mediate such changes was evaluated. RESULTS: Cholestasis patients required lesser oxytocin to elicit four uterine contractions in 10 minutes (1.3+/-0.6 vs 3.6+/-0.8 U, P<.05, n=7) and had lower in vitro ED(50) (1.6 x 10(-10) mol/L vs 1.0 x 10(-8) mol/L, P<.05, n=7) than controls. The 24-hour incubation of control myometrial strips (n=7) with cholic acid (20 micromol/L) increased oxytocin sensitivity. Incubation of cultured myometrial cells (n=5) with cholic acid increased oxytocin-receptor expression (messenger RNA and protein). CONCLUSION: We demonstrate that during intrahepatic cholestasis of pregnancy, an activation of the oxytocin receptor pathway occurs. This event seems to be the result of a cholic acid-mediated increase in oxytocin-receptor expression.

Adult↗

PubMed1981

Effects of bile acids on colon carcinogenesis in rats treated with carcinogens.

Primary bile acids were studied as possible colon tumor promoters or inhibitors in a rat model of chemically induced colon cancer. Cholic acid feeding increased the number of animals with tumors, the number of tumors per animal, and the number of tumors per tumor-bearing animal. Tumor enhancement was attributed to deoxycholic acid, the bacterial metabolite of cholic acid. When chenodeoxycholic acid was fed to the rats in our model, tumor incidence was increased, but the number of tumors per animal and the number of tumors per tumor-bearing animal were similar to controls. The different fecal bile acid pattern obtained with chenodeoxycholic acid may be responsible for the differences in tumor incidence. The methodology to characterize and identify all steroidal components of the feces requires extraction, thin-layer chromatography, gas-liquid chromatography, and gas-liquid chromatography-mass spectrometry. Newer techniques include LH-20 chromatography (for sulfated steroids) and high-pressure liquid chromatography.

Animals↗

PubMed1996

Characterization of lipoproteins during human cholestasis.

We have characterized changes in lipoproteins from cholestatic individuals and reproduced them by incubating lipoproteins from healthy individuals with cholic acid. The cholestatic patients showed an increase in low density lipoprotein (LDL) (>85%), with a smaller proportion of esterified cholesterol, and a fall in high density lipoprotein (HDL) (<10%), with a larger proportion of phospholipids. The protein composition of cholestatic HDL1 was characterized by a smaller proportion of apo A (I, II) and a prominent apo E fraction (39% vs. 9%). These changes involved an increase in degree of molecular packing (order) of HDL1. The addition of cholic acid to serum from healthy individuals altered the lipoprotein distribution, with an increase in LDL, the disappearance of HDL2 and HDL3 and the appearance of HDL1. These HDL1 were characterized by increased phospholipid and reduced apo AI fractions. They also showed a lower density and appeared as spherical particles in contrast to cholestatic HDL. Incubation of healthy HDL with cholic acid in vitro reproduces some of the alteration observed in cholestatic HDL.

Chemical Phenomena↗