Effect of ursodeoxycholic acid on bile secretion and bile components. Comparison with chenodeoxycholic acid and dehydrocholic acid]

Effects of some bile acids on the biliary flow, BSP output and composition (phospholipid, cholesterol, bilirubin and bile acids) were studied in dogs. Ursodeoxycholic acid (UD), chenodeoxycholic acid (CD) and dehydrocholic acid (DC) caused a dramatic increase in biliary flow and BSP output. Relative potencies of these effects were DC greater than CD greater than or equal to UD. UD increased the phospholipid, bile acids and cholesterol concentration but had little effect on bilirubin concentration. Furthermore, UD greatly increased the output of four bile components. CD slightly decreased the phospholipid, cholesterol and bilirubin concentration without the bile acids, while CD increased the output of bile components. After UD or CD administration, the bile acid of each appeared markedly in the bile, dose dependently. On the other hand, DC caused a dramatic decrease of phospholipid, cholesterol and bilirubin concentration but had little effect on bile acids concentration. Output of bile components was increased by DC the first 1 hr but decreased at 2 hr. After DC administration, 3alpha, 7alpha-dihydroxy-12keto-5beta-cholanic acid appeared in the bile while DC did not. Therefore, it is concluded that UD and CD are cholanereticas and DC is a hydrocholeretica.     

Correlation of biliary cholesterol, phospholipids and bile acid compositions and the development of cholesterol cholelithiasis in mice

A study was attempted to establish a screening method for detecting cholelitholytic ingredients from a wide variety of natural substances. Although mice were selected as a suitable pathological model of cholelithiasis to detect a small amount of the ingredients, all the conventional lithogenic diets caused unfavorable influence on the animals. Therefore, as the first step we formulated a new lithogenic diet consisting of butter, cholesterol, cholic acid, etc, which was adequate for mice. Subsequently, the pathological characteristics and persistence of cholelithiasis were examined in the animals; the changes in bile compositions including free and conjugated bile acids, cholesterol and phospholipids were observed before and at the onset of cholelithiasis. Following confirmation of the stone formation, a normal diet was substituted for the lithogenic diet to likewise assess the bile compositions 4 and 6 weeks later. An increasing tendency for deoxycholic acid, disappearance of chenodeoxycholic acid and decrease in ursodeoxycholic acid were seen under the condition of cholelithiasis. In addition, the cholic acid-glycine conjugate which should not exist in the normal state and the increase in free and tauring-conjugated cholic acid were noticed. The biliary cholesterol level in treated mice increased to about 4 times higher than that in untreated mice, while the biliary phospholipids and total bile acids levels increased to only about 1.5 and about 2 times the control levels, respectively. The incidence of stone formation rose sharply at an experimental period between 2 and 3 weeks after starting the lithogenic diet. Gallstones die not disappear even at the 6th week after substituting a normal diet for the lithogenic one. However, the cholic acid-glycine conjugate disappeared, and deoxycholic acid as well as chenodeoxycholic acid and ursodeoxycholic acid tended to recover to the normal levels in the bile.     

Mesophase formation during cholesterol gallstone dissolution in human bile: effect of bile acid composition

Duodenal bile obtained from patients with gallstones who were acutely infused with chenodeoxycholic acid, ursodeoxycholic acid, or cholic acid were examined for the propensity toward the formation of a liquid crystalline mesomorphic phase when cholesterol gallstones were incubated in these bile acids. Bile taken from patients infused with ursodeoxycholic acid was found to be enriched in ursodeoxycholic acid; mesophase formation was detected in these samples but not in bile from patients infused with chenodeoxycholic acid or cholic acid.     

Taurine ameliorates cholesterol metabolism by stimulating bile acid production in high‐cholesterol‐fed rats

This study was designed to investigate the effects of dietary taurine on cholesterol metabolism in high‐cholesterol‐fed rats. Male Sprague‐Dawley rats were randomly divided into two dietary groups (n = 6 in each group): a high‐cholesterol diet containing 0.5% cholesterol and 0.15% sodium cholate, and a high‐cholesterol diet with 5% (w/w) taurine. The experimental diets were given for 2 weeks. Taurine supplementation reduced the serum and hepatic cholesterol levels by 37% and 32%, respectively. Faecal excretion of bile acids was significantly increased in taurine‐treated rats, compared with untreated rats. Biliary bile acid concentrations were also increased by taurine. Taurine supplementation increased taurine‐conjugated bile acids by 61% and decreased glycine‐conjugated bile acids by 53%, resulting in a significant decrease in the glycine/taurine (G/T) ratio. Among the taurine‐conjugated bile acids, cholic acid and deoxycholic acid were significantly increased. In the liver, taurine supplementation increased the mRNA expression and enzymatic activity of hepatic cholesterol 7α‐hydroxylase (CYP7A1), the rate‐limiting enzyme for bile acid synthesis, by three‐ and two‐fold, respectively. Taurine also decreased the enzymatic activity of acyl‐CoA:cholesterol acyltransferase (ACAT) and microsomal triglyceride transfer protein (MTP). These observations suggest that taurine supplementation increases the synthesis and excretion of taurine‐conjugated bile acids and stimulates the catabolism of cholesterol to bile acid by elevating the expression and activity of CYP7A1. This may reduce cholesterol esterification and lipoprotein assembly for very low density lipoprotein (VLDL) secretion, leading to reductions in the serum and hepatic cholesterol levels.     

Hyperalphalipoproteinaemic activity of BRL 26314--I. Enhanced cholesterol turnover in rats

Administration of BRL 26314 [N-(4-chlorobenzyl)-L-phenylalanine] raises circulating high-density lipoprotein (HDL) cholesterol and lowers total triglyceride levels in rats whether maintained on stock or semi-synthetic diets. HDL is also elevated by BRL 26314 in hypothyroid rats and in rats with pre-existing hyperlipidaemia where aortic total cholesterol concentration is decreased. BRL 26314 promotes the excretion of a dose of radiolabelled cholesterol as faecal sterols and bile acids, and decreases the extent of cholesterol-radiolabelling in tissue pools, particularly the aorta and adipose tissue. The increase in cholesterol and bile acid (cholic acid) turnover distinguishes BRL 26314 from a cholestatic agent such as 1-naphthyl isothiocyanate where a superficially similar change in HDL concentration disguises an impaired cholesterol transport. BRL 26314 is not a general protein inducer but part of the mechanism of action may involve enhancement of white adipose tissue lipoprotein lipase activity.     

Modulation of bile acids induced by paraquat in rabbits

Rabbit bile was examined for changes in composition induced by paraquat. Paraquat was administered intraperitoneally and changes in bile components were monitored by high performance liquid chromatography. Alterations in the ratios of total glycine/taurine conjugated bile acids (TGC/TTC), cholic acid/deoxycholic acid (CA/DC), cholic acid/chenodeoxycholic acid (CA/CDC) and cholic acid/cholesterol (CA/CH) were measured as an index of paraquat toxicity. A statistically significant increase in the ratio of TGC/TTC was observed, while CA/DC, CA/CDC and CA/CH showed a decrease. Phospholipids, protein, sugar, bilirubin, beta-carotene, vitamin A and vitamin E in the bile and serum of the experimental animals were also monitored. In bile, the levels of cholesterol, phospholipids, protein, sugar, and total bile acids increased while the levels of the antioxidants beta-carotene, vitamin A and vitamin E decreased. A decrease in the bilirubin content of the bile was also observed. These modifications may be useful clinically for assessment of paraquat toxicity.     

The effect of etofibrate on cholesterol and bile acid metabolism in the hamster

Hamsters were given etofibrate at a dose of 300 mg/kg body wt, by gavage for 5 days, while being fed a chow diet. After treatment, serum cholesterol levels were 27% lower compared to those of the control animals. A similar trend was observed for triglyceride levels. Hepatic lipid levels were unchanged by the treatment. HMG-CoA reductase and acylCoA cholesterol acyltransferase were decreased while cholesterol 7 alpha-hydroxylase was not significantly modified by etofibrate. A choleretic effect and an increase of cholesterol excretion into hepatic bile was observed in treated animals. Nevertheless, composition and cholesterol saturation index of gallbladder bile were similar in control and treated animals. With respect to controls, hepatic bile of treated hamsters contained a lesser amount of cholic and deoxycholic acid and a greater amount of ursodeoxycholic acid.     

Biosynthesis of bile acids in mammalian liver.

The biosynthesis of bile acids in mammalian liver and its regulation, together with the physiological role of bile acids, are reviewed in this article. Bile acids are biosynthesized from cholesterol in hepatocytes. Several steps are involved including epimerisation of the 3beta-hydroxyl group, reduction of the delta4 double bond to the 5beta-H structural arrangement, introduction of alpha-hydroxyl groups at C7 or C7 and C12 and, finally, oxidative degradation of the side chain by three carbon atoms. This gives the primary bile acids, cholic and chenodeoxycholic acids. Cholesterol-7alpha-hydroxylation is the rate determining step in the biosynthesis of cholic and chenodeoxycholic acids. Feedback regulation of cholesterol biosynthesis occurs by various mechanisms including termination of the synthesis of specific cytochromes P-450, modulation of specific cytosol proteins, short-term changes in the process of phosphorylation-dephosphorylation and changes in the capacity of the cholesterol pool as a substrate. Prior to being exported from the liver, bile acids are conjugated with glycine and taurine to produce the bile salts. After excretion into the intestinal tract, primary bile acids are partly converted to secondary bile acids, deoxycholic and lithocholic acids, by intestinal microorganisms. The majority of bile acids is absorbed from the intestinal tract and returned to the liver via the portal blood, so that only a small fraction is excreted in the feces. Bile acids returned to the liver can be reconjugated and reexcreted into the bile in the process of enterohepatic recycling. In addition to the physiological function of emulsifying lipids in the intestinal tract, bile acids are particularly important in respect of their ability to dissolve and transport cholesterol in the bile.     

Hypocholesterolemic effect of bile acid sulfonate analogs in hamsters

We studied the effects of bile acid sulfonate analogs, namely, 3alpha,7alpha,12alpha-trihydroxy-5beta-cholane-24-sulfonate (C-sul), 3alpha,7alpha-dihydroxy-5beta-cholane-24-sulfonate (CDC-sul), and 3alpha,7beta-dihydroxy-5beta-cholane-24-sulfonate (UDC-sul), on serum and liver cholesterol levels, cholesterol 7alpha-hydroxylase activity, and biliary bile acid composition in hamsters fed cholesterol. Of the three analogs studied, UDC-sul slightly but significantly decreased free, esterified, and total cholesterol concentrations in the serum. UDC-sul and CDC-sul reduced liver total cholesterol levels by 25% and 18%, respectively, particularly in the esterified cholesterol fraction. Analysis of biliary bile acids showed the presence of the administered analogs, indicating that sulfonate analogs efficiently participate in enterohepatic cycling. The proportion of cholic acid was increased in all groups fed sulfonate analogs, but the ratio of glycine to taurine conjugated bile acids (G/T) was elevated only in UDC-sul feeding hamsters. There was no significant change in cholesterol 7alpha-hydroxylase activity in hamsters fed C-sul or CDC-sul, while UDC-sul slightly stimulated the enzyme activity compared to the control. The UDC-sul induced decrease in serum and liver cholesterol concentrations may be secondary to enhanced bile acid synthesis. This is supported by the increased cholesterol 7alpha-hydroxylase activity and elevated G/T ratio in biliary bile acids observed following UDC-sul administration.     

Lipid metabolism in liver of rat exposed to cadmium.

We investigated the effect of exposition to cadmium (Cd, 15ppm for 8 weeks) through drinking water on liver lipid metabolism in adult male Wistar rats. As compared to metal non-exposed (control) rats, the serum triglycerides, cholesterol and LDL+VLDL cholesterol concentrations increased. This was associated to a decrease of lipoprotein lipase activity in post heparinic plasma. The VLDL secretion from liver was not modified. Cd treatment increased triglycerides and decreased esterified cholesterol contents in liver. The high triglyceride mass was related to the increased glycerol-3-phosphate acyltransferase mRNA expression. In addition, the liver fatty acids synthesis increased, as determined by an increment of fatty acid synthetase and isocitrate dehydrogenase activities, and [(14)C]-acetate incorporation into saponifiable lipid fraction. The relative percentage of palmitic acid (16:0) and total saturated fatty acids were increased compared with control. Hepatic glucose-6-phosphate dehydrogenase, malic dehydrogenase and cholesteryl ester hydrolase activities were unchanged. In liver, the Cd treatment decreased triglyceride and cholesterol in mitochondria, also increased triglyceride in cytosol, and cholesterol and phospholipid contents in nuclei, compared with control. In addition, an increase of nuclei phosphatidylcholine synthesis was observed. Cd exposure alters directly or indirectly the serum lipid content and liver lipid metabolism.     

Rosuvastatin reduces plasma lipids by inhibiting VLDL production and enhancing hepatobiliary lipid excretion in ApoE*3-leiden mice

The present study was designed to investigate the lipid-lowering properties and mechanisms of action of a new HMG-CoA reductase inhibitor, rosuvastatin, in female ApoE*3-Leiden transgenic mice. Mice received a high fat/cholesterol (HFC) diet containing either rosuvastatin (0 [control], 0.00125%, 0.0025%, or 0.005% [w/w]) or 0.05% (w/w) lovastatin. The highest dose of rosuvastatin reduced plasma cholesterol and triglyceride levels by 39% and 42%, respectively, compared with the HFC control. Lovastatin had no effect on plasma cholesterol and triglyceride levels. In ApoE*3-Leiden mice on a chow diet, rosuvastatin (0.005% [w/w]) decreased plasma cholesterol levels by 35% without having an effect on triglyceride levels. On a chow diet, expression of genes involved in cholesterol biosynthesis and uptake in the liver was increased by rosuvastatin. Further mechanistic studies in HFC-fed mice showed that rosuvastatin treatment resulted in decreased hepatic VLDL-triglyceride and VLDL-apolipoprotein B production. VLDL lipid composition remained unchanged, indicating a reduction in the number of VLDL particles secreted. Lipolytic activity and expression of genes involved in cholesterol and triglyceride synthesis and beta-oxidation of fatty acids in the liver were not affected by rosuvastatin treatment, and hepatic lipid content did not change. However, activity of hepatic diacylglycerol acyltransferase was significantly decreased by 25% after rosuvastatin treatment. Moreover, biliary excretion of cholesterol, phospholipids, and bile acids was increased during treatment. The results indicate that rosuvastatin treatment in ApoE*3-Leiden mice on a HFC diet leads to redistribution of cholesterol and triglycerides in the body, both by reduced hepatic VLDL production and triglyceride synthesis and by enhanced hepatobiliary removal of cholesterol, bile acids, and phospholipids, resulting in substantial reductions in plasma cholesterol and triglyceride levels.     

Hepatic uptake and biliary secretion of bile acids in the perfused rat liver.

Hepatic uptake and biliary secretion have been evaluated in the isolated perfused rat liver for cholic, chenodeoxycholic, ursodeoxycholic acid, both free and taurine-conjugated; the physicochemical properties of the bile acids have also been calculated and related to these experimental parameters. Cholic acid disappearance rate from the perfusate was the fastest, followed by that of ursodeoxycholic and chenodeoxycholic; it was also faster for taurine-conjugated bile acids than for their respective unconjugated forms. The recovery in bile was higher for conjugated than for unconjugated bile acids, and among each class, was higher for cholic than for chenodeoxycholic and ursodeoxycholic. The hepatic uptake correlated negatively (r = -0.99) with the bile acid lipophilicity, while the biliary secretion correlated with the solubility of the molecules. These results show the effect of the physicochemical properties of BA on their hepatic handling, at the physiological concentration of BA in the portal blood.     

Low density lipoprotein-lowering and high density lipoprotein-elevating effects of nicardipine in rats

Oral administration of a calcium antagonist, nicardipine hydrochloride (simply designated as nicardipine), in doses of 10-100 mg/kg tended to decrease total serum cholesterol and to increase high density lipoprotein (HDL) cholesterol in the normal rat. These effects of nicardipine were much greater than those of clofibrate, a standard cholesterol-lowering drug. Neither nicardipine nor clofibrate caused significant alteration in serum triglyceride and phospholipid. In hypercholesterolemic rats, nicardipine increased significantly HDL cholesterol with a reduction of total serum cholesterol, whereas clofibrate did not change HDL cholesterol. Separation of serum lipoproteins either by ultracentrifugation in various densities of KBr-NaCl solution or by polyacrylamide gel electrophoresis demonstrated that nicardipine increased preferentially HDL2 (density: 1.063-1.125), with a reduction of the low density lipoprotein (LDL) (density: 1.006-1.063) level in hypercholesterolemic rats. Serum triglyceride and liver phospholipid were increased slightly by nicardipine with no clear dose-dependency. Clofibrate also increased serum triglyceride. In normal rats, neither nicardipine nor nicotinic acid inhibited sterol biosynthesis from [1-14C]acetate in the liver, whereas clofibrate inhibited sterol production. Oral administration of [4-14C]cholesterol to hypercholesterolemic rats indicated that nicardipine had no inhibitory effect on the intestinal absorption of cholesterol.     

Fecal bile acid excretion and liver cholesterol synthesis after sucralfate and cholestyramine administration in the rat

The relative ability of the resin cholestyramine and sucralfate (disucrose octasulfate) to bind bile acids in the gastro intestinal tract and increase fecal bile acid excretion has been studied in normal rats under standard diet. Plasma and liver cholesterol concentrations and in vitro cholesterol synthesis from 14C-acetate by liver slices, have been determined before and after one and three weeks of drug administration (0.5 or 1.0 g/100 g food). Plasma and liver cholesterol levels were unchanged after one week of treatment, but a moderate decrease in liver cholesterol content was observed after 3 weeks administration of cholestyramine and, to a lesser extent of sucralfate. Both drugs increase fecal bile acid excretion with a definitely higher effect of cholestyramine at either dose or period of administration. However, the resin produced a higher bile acid excretion after one week than after three weeks, whereas sucralfate effect increases with the time of administration. In vitro cholesterogenesis was clearly increased by cholestyramine and moderately by sucralfate although 14C-acetate incorporation into cholesterol was not quantitatively correlated to the amount of bile acid excreted in feces. The potential interest of sucralfate as bile acid sequestrant and hypocholesterolemic agent in man deserves further investigations.     

Bile acids in porcine fetal bile

A study of the biliary bile acid composition in porcine fetus compared with that of the adult pig is described. Biles, collected during gestation (weeks 4, 15 to 17 and at birth), aged six months and two years old, were analyzed by gas-liquid chromatography and capillary GC-MS. Bile acids were separated into different conjugate groups by chromatography on the lipophilic anion exchange gel, piperidinohydroxypropyl Sephadex LH-20. All and one fourth of the total bile acids in the bile of weeks 4 and 15 of gestation, respectively, were present as unconjugated form, however, only a trace of unconjugated bile acids was present in bile of late gestation, the young and the adult pigs. The ratio of glycine/taurine (G/T) conjugates in the conjugated fraction of the fetal bile at 15 weeks gestation was less than 1, which markedly contrasted with the conjugation pattern for adult bile where the ratio of G/T conjugates was approximately more than 9. The predominant acids identified in porcine fetal bile of the 4 weeks gestation were cholic acid (3alpha,7alpha,12alpha-trihydroxy-5beta-chola n-24-oic acid) and chenodeoxycholic acid (3alpha,7alpha -dihydroxy-5beta-cholan-24-oic acid). However, cholic acid in late gestation, young, and adult bile was the smallest component, whereas chenodeoxycholic acid was still the major constituent of these biles. The presence of small but valuable amounts of allocholic acid (3alpha,7alpha,12alpha-trihydroxy-5alpha-chol an-24-oic acid) and cholic acid in early gestation suggested the presence of 12alpha-hydroxylase activity of steroid nucleus in fetal liver. Considerable amounts of glycine-conjugated hyodeoxycholic acid were found in the bile of the gestation periods, suggesting the placental transfer of this bile acid from maternal circulation.     

Effects of Dietary β‐Cyclodextrin in Hypercholesterolaemic Rats

Abstract: β‐Cyclodextrin is a compound that forms inclusion complexes with a variety of molecules, specially bile acids and sterols. This study examines the effects of β‐cyclodextrin on cholesterol and bile acid metabolism in hypercholesterolaemic rats. Male Wistar rats were divided into 4 groups that received during 7 weeks: control diet, 2% cholesterol diet (A), A+2.5% β‐cyclodextrin (B) and A+5% β‐cyclodextrin (C). The cholesterol‐rich diet induced hepatomegaly and fatty liver and significantly reduced cholesterol, bile acid and phospholipid secretion. Addition of β‐cyclodextrin normalised biliary lipid secretion. Moreover, when compared to A, β‐cyclodextrin significantly lowered plasma phospholipid concentration (B: ?21%; C: ?29%) and the liver free/total cholesterol molar ratio (B: ?40%; C: ?38%), increased bile acid faecal output (B: +17%; C: +62%) and enhanced cholesterol 7α‐hydroxylase activity (B:+50%; C: +100%) and mRNA levels (B: +14%; C: +29%). 5% β‐cyclodextrin also reduced plasma triglycerides concentration (?38%). However, ALT and AST activities were significantly increased (B: +140% and +280%; C: +72% and +135%) and there was a high incidence of cell necrosis with portal inflammatory cell infiltration. Addition of β‐cyclodextrin to a cholesterol‐rich diet results in a triglyceride‐lowering action, enhancement of bile acid synthesis and excretion, and normalization of biliary lipid secretion, but produces a marked hepatotoxic effect.     

Free fatty acids in gallstones in mice fed a diet containing cholic acid

In mice, combined addition of 1% cholesterol and 0.5% cholic acid to a diet induced cholesterol gallstones within 40 days as a result of the supersaturation of cholesterol in the bile, as has been reported. The major component of the gallstone was cholesterol, which was measured by HPLC. In this study, however, single addition of 1% cholic acid to a diet, which did not decrease cholesterol solubilizing capacity in bile, contributed to gallstone formation in mice within 50 days. The gallstones thus formed contained a large amount of palmitic acid. In the hepatic bile of this animal, palmitic acid was also detected; however, no solid material was observed by light and polarized-light microscopes. Free fatty acids such as palmitic acid seem to be dissolved in a complex micelle composed of bile acids and lecithin. This probably causes gallstone formation by reducing cholesterol solubilizing capacity in bile.     

Effects of S 21403 on hormone secretion from isolated rat pancreas at different glucose concentrations

The plasma cholesterol-lowering effect and mechanism thereof of a choleretic phloracetophenone or 2,4,6-trihydroxyacetophenone (THA) were investigated in hypercholesterolemic male hamsters. Intragastric administration of THA (300-600 micromol/kg) twice a day for 7 days to these animals caused a dose- and time-dependent decrease in both plasma cholesterol and triglyceride levels. THA at a dose of 400 micromol/kg reduced the cholesterol and triglyceride levels in plasma to 52% and 25% of the level in corresponding cholesterol-fed controls, respectively, with decreases in both plasma very low density lipoprotein and low density lipoprotein cholesterol but not in high density lipoprotein cholesterol. THA did not significantly alter total hepatic cholesterol content but significantly increased the excretion of both bile acids and cholesterol into the intestinal lumen for elimination. Corresponding to the increase in bile acid excretion, THA caused a seven-fold increase in hepatic cholesterol 7alpha-hydroxylase activity. These results suggest that THA exerts its cholesterol lowering effect by increasing hepatic cholesterol 7alpha-hydroxylase activity which increases hepatic conversion of cholesterol to bile acid for disposal via biliary secretion. This compound may have a potential for future development as a therapeutic agent for lowering lipids in hypercholesterolemic patients.     

Urinary bile acid and bile alcohol excretion does not reflect the genetic polymorphism of debrisoquine hydroxylation

Excretion of the major urinary bile alcohol 27-nor-5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 24,25- pentol , and of cholic, chenodeoxycholic, deoxycholic and lithocholic acid was measured in 24 h urine collections of 10 extensive and seven poor metabolizers of debrisoquine. There was no significant difference of the excretion of these cholesterol metabolites between the two groups, indicating that cholesterol hydroxylation to bile alcohols and bile acids is probably not controlled by the same genes responsible for the 'debrisoquine-type' hydroxylation polymorphism.     

Comparison of the choleretic properties of bile acids

The choleretic properties of cholic, chenodeoxycholic, and deoxycholic acid and their taurine and glycine conjugates were compared to their ability to form micelles. It has previously been concluded that deoxycholate has the lowest critical micellar concentration; chenodeoxycholate is slightly higher and cholic is much higher. Conjugation with glycine and taurine has little or no effect on the critical micelle concentration. Since the choleretic properties of bile salts are thought to be directly proportional to their osmotic activities, one might suspect that deoxycholic acid would be the least choleretic, chenodeoxycholic slightly more choleretic and cholic much more choleretic, with little difference between the conjugated and unconjugated forms. However, in the present study, cholic, chenodeoxycholic and taurocholic acid produced similar increases in bile flow (450–700 μl/kg) after an equimolar dose (55 μM/kg). Except for the conjugation of deoxycholic acid with taurine, conjugation of these bile acids with glycine or taurine always decreased the choleretic properties of the bile acids. Therefore, it has been concluded that there is not a good correlation between the in vitro osmotic properties of bile acids and their ability to increase bile flow.