One hundred fifty-one patients with primary biliary cirrhosis (PBC) grouped into four strata based on entry serum bilirubin (<2 mg/dL vs. 2 mg/dL or greater) and liver histology (stages I, 1 1 vs. stages 111, IV-Ludwig criteria) were randomized within each stratum to ursodiol or placebo given in a single dose of 10 to 12 mgkg at bedtime for 2 years. Placebo-(n = 74) and ursodioltreated (n = 77) patients were well matched at baseline for demographic and prognostic factors. Ursodiol induced major improvements in biochemical tests of the liver in strata 1 and 2 (entry bilirubin <2), but had less effect on laboratory tests in patients with entry serum bilirubin of 2 2 (strata 3 and 4). Histology was favorably affected by ursodiol in patients in strata 1 and 2 but not in strata 3 and 4. Ursodiol enrichment in fasting bile obtained at the conclusion of the trial was approximately 40% and comparable in all strata. Thus, differences in ursodiol enrichment of the bile acid pool do not explain better responses of laboratory tests and histology found in patients with less advanced PBC. Patients treated with ursodiol tended to develop a treatment failure less frequently than those who received placebo, particularly in strata 1 and 2 (ursodiol42%, placebo WO, P = .078). Development of severe symptoms (fatigue/pru-Abbreviations: PBC, primary biliary cirrhosis; M-W, Mann-Whitney. From the 'University of Texas Southwestern Medical Center a t Dallas, Dallas, Tx; '

A comprehensive study of the influence of bile acid structure on bile flow and biliary lipid secretion was carried out by infusing pure bile acids at a physiological rate into the proximal small intestine of a bile fistula hamster. Twelve individual bile acids, cholate (C), ursocholate (UC), chenodeoxycholate (CDC), and ursodeoxycholate (UDC) as their glycine (G), taurine (T), or unconjugated form, were studied so that influence of the hydroxy substituents as well as side-chain structure could be defined. The pattern of bile acid output was dependent on bile acid structure and reflected the site and rate of intestinal absorption. Conjugated bile acid output was delayed because of late ileal absorption, and TUC was poorly absorbed. Unconjugated trihydroxy bile acids, C and UC, also exhibited a delay in absorption, while CDC and UDC were absorbed immediately and achieved the highest bile acid output. Unconjugated bile acids were conjugated initially mostly with taurine and then mostly with glycine. The effect of glycine conjugates of each bile acid on bile flow and biliary lipid secretion was similar to that of their corresponding taurine conjugates. All conjugated bile acids induced a similar rate of bile flow (9-15 microliter bile/mumol bile acid), but unconjugated bile acids other than C induced more flow (20-25 microliter bile/mumol bile acid) than their corresponding conjugates. Conjugates of the dihydroxy bile acids induced a greater secretion of phospholipid and cholesterol than cholyl conjugates, whereas conjugates of UC were unique in inducing extremely low phospholipid and cholesterol secretion. For an increase of 1 mumol X min-1 X kg-1 in bile acid output, the increase in phospholipid secretion was 0.072 mumol X min X kg for GCDC and TCDC; 0.051 mumol X min-1 X kg-1 for GUDC and TUDC; and 0.030 mumol X min-1 X kg-1 for GC and TC. Increase in cholesterol output per mumol X min-1 X kg-1 of bile acid output was 0.013 mumol X min-1 X kg-1 for GCDC and TCDC, 0.011 mumol X min-1 X kg-1 for GUDC and TUDC, and 0.005 mumol X min-1 X kg-1 for GC and TC. In general, unconjugated bile acids induced more phospholipid and cholesterol than their corresponding conjugates; however, the rank-order effect of the steroid nucleus substituents was similar to that observed for the respective conjugates. These results indicate that both nuclear and side-chain structure influence the enterohepatic circulation and biliary secretory properties of bile acids.(ABSTRACT TRUNCATED AT 400 WORDS)

When secreted into bile, unconjugated dihydroxy bile acids are absorbed passively by cholangiocytes according to the cholehepatic circulation hypothesis. A fraction of these are likely to be conjugated during transcellular transport. Experiments were performed using fluorescent conjugated bile acids to test whether carrier-mediated transport of conjugated bile acids is present in the basolateral domains of polarized cholangiocytes of intrahepatic bile ductules isolated from rat liver. The time course of the cellular localization of cholyl-NBDAB-Gly and chenodeoxycholyl-NBDAB-Gly, which are anionic fluorescent derivatives of the corresponding glycine-conjugated bile acids, was characterized using an image-analysis system. With 0.3-3 microM solutions, fluorescence was present at 1 and 3 min in the basolateral area of cholangiocytes. Staining in the apical region occurred later, with a peak after 15 min of incubation. The basolateral uptake of the two fluorescent bile acids was temperature dependent and Na+ independent, and was not influenced by the addition of amiloride, by lowering of the medium pH to 6.0, or by preincubation with valinomycin. Uptake was partially inhibited by the absence of Cl- or HCO3- in the perfusate, by preincubation with 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), and by the presence of different organic anions or unconjugated and conjugated bile acids in the medium. When cells were preloaded with an ethyl ester of chenodeoxycholyl-NBDAB-Gly, which is hydrolyzed by intracellular esterases, the decrease of cell fluorescence was partly inhibited by H2DIDS, whereas it was stimulated by the presence of 20 microM cholyltaurine in the medium. It is concluded that transport of conjugated bile acid anions across the basolateral membrane of the polarized rat cholangiocyte is carrier mediated. The conjugated bile acid transporter is likely to be an anion exchanger and is likely to be involved in bile secretion whenever conjugated bile acids or other organic anions are transported from the base of the biliary ductular epithelial cells into the plasma of the periductular capillary plexus.

The biliary recovery and effect on bile flow and biliary bicarbonate secretion of infused norchenodeoxycholate (nor-CDC), the synthetically prepared C23 homologue of chenodeoxycholate (CDC), were defined in the anesthetized biliary fistula hamster, rat, and guinea pig and compared with those of its taurine conjugate as well as those of the natural C24 bile acid, CDC. In the hamster and rat, nor-CDC was recovered slowly in bile in contrast to its taurine conjugate or CDC. Hepatic biotransformation of nor-CDC was complex. Little amidation with glycine or taurine occurred and the compound was recovered in bile in unchanged form, in the form of hydroxylated derivatives as well as glucuronates and sulfates, the proportion varying in the different species. In contrast, CDC was efficiently amidated with glycine or taurine. The taurine conjugate of nor-CDC was secreted largely unchanged. Nor-CDC infusion caused a striking hypercholeresis in the hamster (108 microliters bile/mumol bile acid in bile) and in the rat (220 microliters/mumol); these values for bile acid-dependent flow far exceed those reported for any other natural bile acid to date in these species. The induced hypercholeresis was of canalicular origin and was accompanied by an enrichment in bicarbonate ion concentration as well as increased bicarbonate output. The taurine conjugate of nor-CDC did not display hypercholeretic properties in the hamster. In the guinea pig, whose native bile is bicarbonate-rich relative to other species, nor-CDC was only mildly hypercholeretic relative to CDC and caused no change in bicarbonate concentration. Thus shortening the side chain of a natural dihydroxy bile acid by a single carbon atom formed a compound that underwent a different hepatic biotransformation than that of most natural bile acids and induced a bicarbonate-rich canalicular choleresis far greater than that which can be explained by current theories of bile formation.

To define the metabolism of 7-ketolithocholic acid in man, studies were carried out in gallstone patients with normal liver function. 7-[24-14C]ketolithocholic acid or its glycine or taurine conjugates were injected intravenously, and the chemical form of radioactivity appearing in bile was determined to define hepatic biotransformation. To study intestinal absorption 7-[24-14C]ketolithocholic acid was infused into the jejunum and ileum, respectively, and the chemical form of radioactivity appearing in peripheral blood and bile was assessed. 7-Ketolithocholic acid was extensively reduced in the liver to chenic acid and, to lesser extent, to ursodeoxycholic acid. Hepatic reduction was similar for both unconjugated as well as glycine- and taurine-conjugated 7-ketolithocholic acid. 7-Ketolithocholic acid was well absorbed. There was no biotransformation in the small intestinal lumen or during absorption, because all radioactivity recovered from the lumen or in peripheral blood was in unchanged 7-ketolithocholic acid. Biotransformation products in bile after jejunal infusion were similar to those after intravenous injection. The studies indicate that 7-ketolithocholic acid is likely to be a physiological precursor of ursodeoxycholic acid in healthy man.