Determination of individual serum bile acids in chronic liver diseases: Fasting levels and results of oral chenodeoxycholic acid tolerance test

Fifteen bile acids in serum of 5 normal subjects and 21 patients with chronic liver diseases were fractionated by high performance liquid chromatography. Fasting total bile acids (TBA), glycocholic acid, taurocholic acid, glycochenodeoxycholic acid (GCDCA), and taurochenodeoxycholic acid (TCDCA) were significantly increased in patients with liver cirrhosis as compared with normal subjects. The cholic acid (CA) level and the ratio of the sum of free and conjugated CA to the sum of free and conjugated chenodeoxycholic acid (CDCA) were significantly elevated in patients with compensated as compared with decompensated liver cirrhosis, and were useful for differentiation of the two conditions. Serum bile acid levels were determined after oral administration of 500 mg of CDCA in the 5 normal subjects and 11 patients with liver disease. The TBA level reached a peak 90 min after CDCA administration in patients with chronic hepatitis and after 120 min in those with liver cirrhosis. The increase in the TBA level was significantly greater in patients with liver disease than in normal subjects. CDCA, GCDCA, and TCDCA showed changes similar to those in TBA. In patients with decompensated liver cirrhosis, the reduction in the TBA and CDCA levels after the peaks was slow, and GCDCA and TCDCA levels continued to increase until 180 min after the administration of CDCA. The TBA and CDCA levels 180 min after CDCA administration were significantly different among normal subjects, patients with chronic hepatitis, those with compensated liver cirrhosis, and those with decompensated liver cirrhosis, suggesting the usefulness of CDCA administration in differentiation of these conditions.     

肝硬化患者中血清总胆汁酸测定的临床意义

背景：胆汁酸在肝内合成和分泌，因此可以作为反映肝细胞损害的指标之一。目的：探讨肝硬化患者血清总胆汁酸（TBA）测定的临床意义。方法：收集42例肝硬化患者的肝功能资料，比较TBA与其他常规肝功能指标的敏感性差异。结果：肝硬化组的TBA显著高于健康对照组（P＜0．01），其水平为健康对照组的6．9倍，异常率为74％，显著高于丙氨酸转氨酶（ALT）、γ－谷氨酰转移酶（γ－GT）和碱性磷酸酶（ALP）（P＜0．01）。肝硬化失代偿期患者的TBA水平显著高于代偿期患者（P＜0．01）。结论：TBA是反映肝硬化患者肝细胞损害的敏感指标之一。     

A combination therapy of vitamin K1 and bile acid on hemorrhagic diathesis in patients with decompensated liver cirrhosis

This paper presents a study of treatment involving vitamin K1 (VK1) accompanied by bile acids for hemorrhagic diathesis that was applied 42 times in 35 patients with decompensated liver cirrhosis. The hepaplastin test (HPT) value showed no change during the administration of VK1 alone. The HPT value elevated significantly, however, after the administration of VK1 with bile acid, especially when using ursodeoxycholic acid (UDCA). The HPT value in patients treated with VK1 in addition to UDCA before treatment with 53.2% +/- 10.2% (mean +/- SD) and after that for 2.1 +/- 1.1 months (mean +/- SD) with 74.7 +/- 16.8% showed a significant difference (p less than 0.001). On the other hand, no significant difference was noted between the HPT value of 57.2 +/- 13.6% before and that of 62.9 +/- 13.9% after the treatment in patients treated using VK1 in conjunction with chenodeoxycholic acid (CDCA). These results indicate that the therapy incorporating VK1 and bile acid, especially UDCA, is useful for reducing the hemorrhagic tendency in patients with decompensated liver cirrhosis who show no improvement using VK1 alone.     

乙型肝炎患者血脂、血清前白蛋白和总胆汁酸变化的意义

目的探讨乙型肝炎患者血脂、血清前白蛋白和总胆汁酸的变化规律,了解其与病情及预后的关系。方法在230例乙型肝炎患者[其中急性肝炎43例,慢性肝炎91例(轻度25例,中度32例,重度34例),重型肝炎33例,肝炎肝硬化63例]和50例正常人,测定血清总胆固醇(TC)、甘油三酯(TG)、高密度脂蛋白(HDL)、血清前白蛋白(PA)、白蛋白(ALB)、总胆汁酸(TBA)水平。结果各组总胆汁酸水平较正常对照组升高,差别有显著性意义(P<0·05);慢性肝炎组、肝硬化组、重型肝炎组患者血清甘油三脂、总胆固醇、HDL-C、血清前白蛋白、白蛋白水平均较正常对照组降低,差别有显著性意义(P<0.05);各项血脂水平随着肝功能损害的加重而降低(慢性肝炎重度组和中度组显著低于轻度组,重型肝炎组显著低于慢性肝炎组和肝硬化组)。结论检测乙型肝炎患者血脂、血清前白蛋白和总胆汁酸水平,对了解肝功能状态和估计预后均有一定的意义。     

Changes in portal blood flow by intravenous administration of glucagon--the relationship between those changes and the total serum bile acid values in UDCA.GLUCAGON tolerance test

G30TBA is the total serum bile acid concentration obtained thirty minutes after injection of glucagon in the UDCA.GLUCAGON tolerance test. We have previously reported the usefulness of G30TBA in evaluating liver function. In this paper, changes in the portal blood flow in response to glucagon administration are measured and the relationship between those changes and G30TBA studied. We used an ultrasonic duplex system composed of a B-mode scanner and doppler flow meter of measure portal blood flow after injection of glucagon in thirty seven patients with chronic liver diseases. The results are as follows: The increase in portal blood flow by exogenous glucagon in liver cirrhosis is statistically significantly lower than that in chronic hepatitis. G30TBA in the good-response-to-glucagon group is statistically significantly lower than that in the poor-response group. These results suggest that the effect of glucagon on portal blood flow significantly influences the serum bile acid concentration in the UDCA.GLUCAGON tolerance test.     

胱抑素C、血浆尾加压素Ⅱ在失代偿期肝硬化合并肝肾综合征患者中的诊断价值

目的探讨胱抑素C（CysC）、血浆尾加压素Ⅱ（uⅡ）在失代偿期肝硬化合并肝肾综合征（HRS）患者中的诊断价值。方法收集2011年2月-2011年11月于常州市第一人民医院消化内科住院的失代偿期肝硬化患者50例,计算其校正内生肌酐清除率（Ccr）,并根据Ccr分为单纯肝硬化组、亚临床HRS组及HRS组,以15例健康体检者为对照组,检测ALT、AST、总胆汁酸（TBA）、Alb、血清肌酐（Scr）、CysC、uⅡ浓度,比较各组上述指标的差异,若数据成正态分布且方差齐,进行单因素方差分析（One-Way ANOVA）,两组间比较采用t检验;否则,多组间进行非参数秩和检验（Kruskall-Wallis H test）,两组间比较使用Mann-Whjtney U检验。相关分析采用Spearman相关检验。并通过绘制CysC、uⅡ浓度判断肝硬化合并亚临床HRS及HRS的ROC曲线,获得其曲线下面积（AUC）及最佳临界值。结果肝硬化病例组与正常对照组ALT、AST、TBA、Alb、Scr、Cysc、uⅡ比较差异有统计学意义。单纯肝硬化组、亚临床HRS组及HRS组CysC、uⅡ浓度均呈升高趋势,差异具有统计学意义（P〈0.05）。CysC和uⅡ判断亚临床HRS的AUC分别为0.91和0.867,其最佳临界值分别为1.40 mg/L、299.06 pg/ml。CysC和uⅡ判断HRS的AUC分别为0.942和0.901,其最佳临界值分别为2.22 mg/L、321pg/ml。结论 CysC、uⅡ浓度在患者血清肌酐正常时就出现升高改变,有助于早期发现亚临床HRS。CysC、uⅡ浓度对失代偿期肝硬化患者并发亚临床HRS及HRS有很好的判别价值。     

A combination therapy of vitamin K1 and bile acid on hemorrhagic diathesis in patients with decompensated liver cirrhosis

This paper presents a study of treatment involving vitamin K₁ (VK₁) accompanied by bile acids for hemorrhagic diathesis that was applied 42 times in 35 patients with decompensated liver cirrhosis. The hepaplastin test (HPT) value showed no change during the administration of VK₁ alone. The HPT value elevated significantly, however, after the administration of VK₁ with bile acid, expecially when using ursodeoxycholic acid (UDCA). The HPT value in patients treated with VK₁ in addition to UDCA before treatment with 53.2% ± 10.2% (mean ± SD) and after that for 2.1 ± 1.1 months (mean ± SD) with 74.7 ± 16.8% showed a significant difference (p< 0.001). On the other hand, no significant difference was noted between the HPT value of 57.2 ± 13.6% before and that of 62.9 ± 13.9% after the treatment in patients treated using VK₁ in conjunction with chenodeoxycholic acid (CDCA). These results indicate that the therapy incorporating VK₁ and bile acid, especially UDCA, is useful for reducing the hemorrhagic tendency in patients with decompensated liver cirrhosis who show no improvement using VK₁ alone.     

Thallium-201 per rectum for the diagnosis of cirrhosis in patients with asymptomatic chronic hepatitis

In normal subjects, thallium-201, administered per rectum, is taken up mainly by the liver (heart/liver ratio in normal subjects: 0.04 to 0.12). It has been claimed that an increased heart/liver ratio is suggestive of portal-caval shunting and portal hypertension. To evaluate the possibility of using thallium-201 as a test to diagnose cirrhosis, we administered this substance per rectum to 33 patients with biochemical evidence, but no clinical symptoms, of liver disease. Laparoscopy and liver biopsy revealed chronic active hepatitis without cirrhosis in 18 patients, and chronic active hepatitis with cirrhosis in the others. The results of conventional liver function tests were similar in both groups. A significant difference, however, was found between the means of fasting serum bile acid concentrations (9.8 +/- 3.2 and 18.3 +/- 4.2 microM per liter) in chronic active hepatitis without cirrhosis and cirrhotic patients, and between the means of the heart/liver ratios 20 min after thallium-201 administration (heart/liver: 0.09 +/- 0.03 and 0.54 +/- 0.13, respectively). Unlike the serum bile acid concentration which gave some overlapping values, the thallium-201 test clearly distinguished the chronic active hepatitis without cirrhosis group from the cirrhotics. In the cirrhotic group, there was a significant correlation between the heart/liver ratio and signs of portal hypertension such as esophageal varices, increased diameter of the vena porta and hypersplenism. The thallium-201 test is therefore useful in discriminating between chronic active hepatitis with and without cirrhosis in clinically asymptomatic subjects with biochemical evidence of moderate liver function impairment. A heart/liver uptake ratio much higher than normal (above 0.30) strongly suggests the development of hepatic cirrhosis.     

Urinary bile acid sulfate levels in patients with hepatitis C virus-related chronic liver diseases

Aim:  Urinary bile acids are mainly conjugated with sulfuric acid, and urinary sulfated bile acid (USBA) levels in hepatobiliary diseases have been reported. However, the relationship between USBA and fasting serum total bile acid (TBA) has not been studied in hepatobiliary diseases. In the present study, we measured USBA levels in patients with hepatitis C virus-related chronic liver diseases, and the relationship between TBA and various laboratory tests was studied.
Methods:  USBA was measured using an automatic assay kit in 66 patients with chronic hepatitis and 28 patients with liver cirrhosis, and its relationship between TBA and various laboratory tests was studied.
Results:  The median USBA level was 10.7 µmol/g creatinine in patients with chronic hepatitis and 41.1 µmol/g creatinine in liver cirrhosis ( P  = 0.000). More patients with chronic hepatitis had elevated USBA levels (61%) compared to TBA level (39%) ( P  = 0.002). USBA level was well correlated with TBA (r_s = 0.680), and negatively correlated with albumin (r_s = −0.488), prothrombin time (r_s = −0.385) and platelet counts (r_s = −0.394). In patients with liver cirrhosis, USBA was significantly elevated in Child–Pugh class B compared to Child–Pugh class A ( P  = 0.036).
Conclusion:  Although the metabolic pathways of USBA and TBA are different, these levels correlated very well, and USBA is considered to be a useful indicator of hepatic function like TBA in patients with chronic hepatitis C.     

The relationship between postprandial bile acid concentration, GLP-1, PYY and ghrelin

Background Gut hormones peptide YY (PYY) and glucagon‐like peptide‐1 (GLP‐1) play an integral role in appetite control and energy homeostasis. Entero‐endocrine L‐cells can be stimulated by nutrients and or bile acids to co‐secrete PYY and GLP‐1. The aim of this study was to determine the response of bile acids, PYY, GLP‐1 and ghrelin after a test meal. Design Twelve subjects with a BMI of 22·8 (0·52) kg/m² [mean (SEM)] received a 400 kcal test meal after which blood samples were taken every 30 min from 0 to 180 min. PYY, GLP‐1 and ghrelin were measured by radioimmunoassays. Fractionated bile acids were measured by HPLC‐MSMS. Results PYY positively correlated with glycochenodeoxycholic acid (GCDCA) (rs = 0·23, P = 0·03) and taurochenodeoxycholic acid (TCDCA) (rs = 0·26, P = 0·02). GLP‐1 positively correlated with GCDCA (rs = 0·22, P = 0·047) and glycodeoxycholic acid (GDCA) (rs = 0·3, P = 0·005). Ghrelin negatively correlated with GDCA (rs = ?0·45, P≤ 0·0001), TCDCA (rs = ?0·23, P = 0·034) and taurodeoxycholic acid (TDCA) (rs = ?0·44, P≤ 0·0001). Conclusion PYY and GLP‐1 responses correlated with chenodeoxycholic acid (CDCA) counterparts, whereas ghrelin negatively correlated with deoxycholic acid (DCA) counterparts. Specific bile acids may thus differentially affect entero‐endocrine cells.     

Bile acids influence hepatic chemiluminescence in normal and oxidative-stressed rats†

The aim of the present study was to clarify whether bile acids influence chemiluminescence (CL) in the liver in vivo. Hepatic CL was determined on the surface of the liver of anaesthetized rats by using a photon counter. In normal rats, hepatic CL was significantly decreased 30 min after enteral administration of chenodeoxycholic acid (CDCA) or deoxycholic acid (DCA), but returned to its initial level 3 h later, after part of the CDCA administered was metabolized. Ursodeoxycholic acid (UDCA) and cholic acid had no effect on CL. In contrast, hepatic CL was markedly increased 30 min after CDCA or DCA administration in rats given either buthionine sulphoximine (BSO), an inhibitor of γ-glutamylcysteine synthetase, or diethyldithiocarbamate (DDC), an inhibitor of both superoxide dismutase and glutathione peroxidase. Chenodeoxycholic acid further increased the CL of BSO- or DDC-treated rats during inhalation of oxygen via a tracheal cannula. Coadministration of UDCA eliminated the effects of CDCA on the hepatic CL of normal and BSO- or DDC-treated rats with or without oxygen inhalation. We conclude that cytotoxic bile acids, such as CDCA, increase CL in the antioxidants-depleted or oxidative-stressed liver in vivc, but that UDCA prevents CDCA from developing CL.     

Feedback regulation of bile acid synthesis in primary human hepatocytes: evidence that CDCA is the strongest inhibitor

Primary human hepatocytes were used to elucidate the effect of individual bile acids on bile acid formation in human liver. Hepatocytes were treated with free as well as glycine-conjugated bile acids. Bile acid formation and messenger RNA (mRNA) levels of key enzymes and the nuclear receptor short heterodimer partner (SHP) were measured after 24 hours. Glycochenodeoxycholic acid (GCDCA; 100 micromol/L) significantly decreased formation of cholic acid (CA) to 44% +/- 4% of controls and glycodeoxycholic acid (GDCA) decreased formation of CA to 67% +/- 11% of controls. Glycoursodeoxycholic acid (GUDCA; 100 micromol/L) had no effect. GDCA or glycocholic acid (GCA) had no significant effect on chenodeoxycholic acid (CDCA) synthesis. Free bile acids had a similar effect as glycine-conjugated bile acids. Addition of GCDCA, GDCA, and GCA (100 micromol/L) markedly decreased cholesterol 7alpha-hydroxylase (CYP7A1) mRNA levels to 2% +/- 1%, 2% +/- 1%, and 29% +/- 11% of controls, respectively, whereas GUDCA had no effect. Addition of GDCA and GCDCA (100 micromol/L) significantly decreased sterol 12alpha-hydroxylase (CYP8B1) mRNA levels to 48% +/- 5% and 61% +/- 4% of controls, respectively, whereas GCA and GUDCA had no effect. Addition of GCDCA and GDCA (100 micromol/L) significantly decreased sterol 27-hydroxylase (CYP27A1) mRNA levels to 59% +/- 3% and 60% +/- 7% of controls, respectively, whereas GUDCA and GCA had no significant effect. Addition of both GCDCA and GDCA markedly increased the mRNA levels of SHP to 298% +/- 43% and 273% +/- 30% of controls, respectively. In conclusion, glycine-conjugated and free bile acids suppress bile acid synthesis and mRNA levels of CYP7A1 in the order CDCA > DCA > CA > UDCA. mRNA levels of CYP8B1 and CYP27A1 are suppressed to a much lower degree than CYP7A1.     

Clinical Significance of Fasting Serum Bile Acid in the Long-Term Observation of Chronic Liver Disease

Fasting serum bile acid (FSBA) was serially measured by a fluorescent enzyme method in a follow-up study of 61 patients with chronic liver disease. In chronic inactive hepatitis, fluctuation of FSBA was within the normal range in both the exacerbated state and in remission. In chronic active hepatitis, FSBA was abnormally elevated in both states, but the difference was not significant. In chronic active hepatitis where FSBA was elevated in the remission state above its value in the exacerbated state, exacerbation of the disease occurred repeatedly during the follow-up period. In compensated liver cirrhosis progressing into the decompensated form, FSBA levels increased before a decrease in the serum values of albumin, cholesterol, and cholinesterase, and an elevation of bilirubin. In liver cirrhosis, FSBA levels increased above 100 microM, 1-4 months before the appearance of ascites.     

Urinary bile acid sulfate levels in patients with primary biliary cirrhosis

Aim: Urinary bile acids are mainly conjugated with sulfuric acid. In a previous work, we demonstrated that the levels of urinary sulfated bile acids (USBA) and serum total bile acids (TBA) were correlated very well and also that USBA was considered to be a more useful indicator of hepatic fibrosis than TBA in patients with hepatitis C virus (HCV)‐related liver diseases. In the current study we aimed to confirm these finding in patients with primary biliary cirrhosis (PBC), a prototypic cholestatic liver disease. Methods: Urinary sulfated bile acids were measured using an automatic assay kit in 50 patients with PBC, of whom 11 were diagnosed as having cirrhosis. We obtained specimens before ursodeoxycholic acid (UDCA) administration in four patients, and during UDCA in 46 patients. The correlations between USBA and various laboratory tests were studied. Results: The median USBA level was 67.9 µmol/g creatinine in PBC; 27.7 without cirrhosis and 210.3 with cirrhosis (P = 0.001). The number of PBC patients with elevated USBA was significantly higher than those with elevated TBA (82% vs. 56%). This significance was remarkable especially in early stages, non‐cirrhotic patients (77% vs. 49%). USBA level was well correlated with TBA (r_s = 0.72), and negatively correlated with platelet (r_s = ?0.34) and albumin (r_s = ?0.31). Conclusion: Urinary sulfated bile acids and TBA are well correlated, and together with the findings that USBA is not affected by meals, USBA is considered to be more beneficial and convenient than TBA for earlier detection of fibrosis in PBC.     

Plasma levels of pipecolic acid in patients with chronic liver disease

Plasma levels of pipecolic acid, which is a minor metabolite of lysine, were determined by high-performance liquid chromatography in 22 patients with chronic liver disease, composed of 6 patients with chronic active hepatitis, 11 with liver cirrhosis and 5 with hepatocellular carcinoma. The plasma levels of pipecolic acid, when compared to those in normal subjects (1.00 +/- 0.08 nmoles per ml), were found to be significantly elevated (p less than 0.01) in patients with liver cirrhosis (1.93 +/- 0.24 nmoles per ml) and hepatocellular carcinoma (2.22 +/- 0.49 nmoles per ml), but did not show any significant change in patients with chronic active hepatitis. Plasma levels of pipecolic acid correlated positively with serum bile acid and bilirubin, and negatively with indocyanine green disappearance rate, cholinesterase and prothrombin time but not with plasma lysine levels. These results suggest that plasma levels of pipecolic acid increase almost parallel to the severity of liver damage, and that this increase in pipecolic acid may reflect the injury of liver peroxisomes which appear to be related to the degradation of pipecolic acid.     

Kinetics and pool size of chenodeoxycholic acid in cholesterol gallstone patients.

The pool size, half life, and daily production rate of chenodeoxycholic acid (CDCA) was determined by the isotope dilution method upon intravenous injections of about 10 muCI OF 24-14C-CDCA in 7 patients with radiolucent gallstones in functioning gallbladders, and 9 healthy controls. Bile was obtained by duodenal intubation. The method also allowed measurement of the CDCA percentage of total bile acids (TBA) and an indirect calculation of the TBA pool size. The pool size and daily production rate of CDCA were slightly, but not significantly, diminished in the gallstone patients. The half life of CDCA was almost equal in the 2 groups. The CDCA percentage of TBA was significantly higher in the gallstone patients (0.02 less than P less than 0.05), and the TBA pool size was significantly reduced (P less than 0.01) in the gallstone patients. It is concluded that the CDCA metabolism is similar to that of cholic acid in gallstone patients. Thus the formation of gallstones is hardly due to specific alterations in CDCA metabolism, suspected on account of the specific cholelitholytic effect of CDCA ingestion. The significance of increased CDCA percentage in bile is discussed in relation to the results from other study groups, and it is pointed out that a relative increase in the bile content of dihydroxy bile acids may lead to reduced cholesterol holding capacity of bile, and thus favor the formation of gallstones.     

Conjugated bile acids promote ERK1/2 and AKT activation via a pertussis toxin-sensitive mechanism in murine and human hepatocytes

Several studies have argued that G-protein-coupled receptors (GPCR) have the capacity to promote activation of receptor tyrosine kinases. The current studies were performed to examine the regulation of the extracellular regulated kinase (ERK)1/2 and AKT pathways by conjugated and unconjugated bile acids in primary hepatocytes. Deoxycholic acid (DCA), chenodeoxycholic acid (CDCA), taurodeoxycholic acid (TDCA), glycodeoxycholic acid (GDCA), taurochenodeoxycholic acid (TCDCA), glycochenodeoxycholic acid (GCDCA), taurocholic acid (TCA), glycocholic acid (GCA), and tauroursodeoxycholic acid (TUDCA) all activated ERK1/2 in primary rat hepatocytes that was abolished by inhibition of ERBB1, and significantly reduced by ROS quenching agents. Bile acid-induced AKT activation was blunted by preventing ERBB1 activation and ROS generation. Treatment of rat hepatocytes with pertussis toxin (PTX) did not alter ERK1/2 and AKT activation induced by DCA or CDCA but abolished pathway activations by conjugated bile acids. Similar data to those with PTX were obtained when a dominant negative form of G(i1alpha) was overexpressed. Treatment of rat hepatocytes with TDCA and TCA promoted guanosine triphosphate (GTP) loading of G(i1alpha), G(i2alpha), and G(i3alpha) in vitro. Treatment of rat hepatocytes with PTX abolished TDCA-induced tyrosine phosphorylation of ERBB1. Similar findings to those in rat hepatocytes were also obtained in primary mouse and human hepatocytes, but not in established rodent or human hepatoma cell lines. In conclusion, collectively our findings demonstrate that unconjugated bile acids activate hepatocyte receptor tyrosine kinases and intracellular signaling pathways in a ROS-dependent manner. In contrast, conjugated bile acids primarily activate receptor tyrosine kinases and intracellular signaling pathways in a GPCR (G(ialpha))-dependent and ROS-dependent manner.     

Effect of ursodeoxycholic acid on the kinetics of the major hydrophobic bile acids in health and in chronic cholestatic liver disease.

Beneficial effects of ursodeoxycholic acid in chronic cholestatic liver diseases have been attributed to displacement of hydrophobic bile acids from the endogenous bile acid pool. To test this hypothesis, we determined pool sizes, fractional turnover rates, synthesis/input rates and serum levels of deoxycholic acid and chenodeoxycholic acid before and 1 mo after the start of treatment with ursodeoxycholic acid (13 to 15 mg/kg body wt/day) in four healthy volunteers and five patients with chronic cholestatic liver diseases (three with primary biliary cirrhosis and two with primary sclerosing cholangitis). Bile acid kinetics were determined by combined capillary gas chromatography-isotope ratio mass spectrometry in serum samples after administration of [2H4] deoxycholic acid and [13C]chenodeoxycholic acid. In healthy volunteers, deoxycholic acid pool sizes decreased during administration of ursodeoxycholic acid by 72%. In patients with cholestatic liver diseases, deoxycholic acid pool sizes before ursodeoxycholic acid treatment were only 13% of those in healthy volunteers and were unaffected by ursodeoxycholic acid treatment. Chenodeoxycholic acid pool sizes were not different in healthy volunteers and in patients with cholestatic liver disease, and were not altered by ursodeoxycholic acid treatment. In both healthy volunteers and patients with cholestatic liver disease, synthesis/input rates and serum levels of deoxycholic acid and chenodeoxycholic acid were not altered by ursodeoxycholic acid treatment. Because in our patients improvement of serum liver tests during short-term ursodeoxycholic acid treatment was noted without a decrease of the pool sizes of the major hydrophobic bile acids, we conclude that displacement of hydrophobic endogenous bile acids is not the mechanism of action of ursodeoxycholic acid in chronic cholestatic liver disease.