The effects of intraduodenal bile acid administration on biliary secretion of ionized calcium and carbonate in man

UDCA for Drug-Induced Liver Disease: Clinical and Pathophysiological Basis

Drug-induced liver injury (DILI) is an adverse reaction to medications and other xenobiotics that leads to liver dysfunction. Based on differential clinical patterns of injury, DILI is classified into hepatocellular, cholestatic, and mixed types; although hepatocellular DILI is associated with inflammation, necrosis, and apoptosis, cholestatic DILI is associated with bile plugs and bile duct paucity. Ursodeoxycholic acid (UDCA) has been empirically used as a supportive drug mainly in cholestatic DILI, but both curative and prophylactic beneficial effects have been observed for hepatocellular DILI as well, according to preliminary clinical studies. This could reflect the fact that UDCA has a plethora of beneficial effects potentially useful to treat the wide range of injuries with different etiologies and pathomechanisms occurring in both types of DILI, including anticholestatic, antioxidant, anti-inflammatory, antiapoptotic, antinecrotic, mitoprotective, endoplasmic reticulum stress alleviating, and immunomodulatory properties. In this review, a revision of the literature has been performed to evaluate the efficacy of UDCA across the whole DILI spectrum, and these findings were associated with the multiple mechanisms of UDCA hepatoprotection. This should help better rationalize and systematize the use of this versatile and safe hepatoprotector in each type of DILI scenarios.

Ursodeoxycholic acid in cholestasis: linking action mechanisms to therapeutic applications

UDCA (ursodeoxycholic acid) is the therapeutic agent most widely used for the treatment of cholestatic hepatopathies. Its use has expanded to other kinds of hepatic diseases, and even to extrahepatic ones. Such versatility is the result of its multiple mechanisms of action. UDCA stabilizes plasma membranes against cytolysis by tensioactive bile acids accumulated in cholestasis. UDCA also halts apoptosis by preventing the formation of mitochondrial pores, membrane recruitment of death receptors and endoplasmic-reticulum stress. In addition, UDCA induces changes in the expression of metabolizing enzymes and transporters that reduce bile acid cytotoxicity and improve renal excretion. Its capability to positively modulate ductular bile flow helps to preserve the integrity of bile ducts. UDCA also prevents the endocytic internalization of canalicular transporters, a common feature in cholestasis. Finally, UDCA has immunomodulatory properties that limit the exacerbated immunological response occurring in autoimmune cholestatic diseases by counteracting the overexpression of MHC antigens and perhaps by limiting the production of cytokines by immunocompetent cells. Owing to this multi-functionality, it is difficult to envisage a substitute for UDCA that combines as many hepatoprotective effects with such efficacy. We predict a long-lasting use of UDCA as the therapeutic agent of choice in cholestasis.

Combination of ursodeoxycholic acid and glucocorticoids upregulates the AE2 alternate promoter in human liver cells

Primary biliary cirrhosis (PBC) is a cholestatic disease associated with autoimmune phenomena and alterations in both biliary bicarbonate excretion and expression of the bicarbonate carrier AE2. The bile acid ursodeoxycholic acid (UCDA) is currently used in treatment of cholestatic liver diseases and is the treatment of choice in PBC; however, a subset of PBC patients respond poorly to UDCA monotherapy. In these patients, a combination of UDCA and glucocorticoid therapy appears to be beneficial. To address the mechanism of this benefit, we analyzed the effects of UDCA and dexamethasone on AE2 gene expression in human liver cells from hepatocyte and cholangiocyte lineages. The combination of UDCA and dexamethasone, but not UDCA or dexamethasone alone, increased the expression of liver-enriched alternative mRNA isoforms AE2b1 and AE2b2 and enhanced AE2 activity. Similar effects were obtained after replacing UDCA with UDCA conjugates. In in vitro and in vivo reporter assays, we found that a UDCA/dexamethasone combination upregulated human AE2 alternate overlapping promoter sequences from which AE2b1 and AE2b2 are expressed. In chromatin immunoprecipitation assays, we demonstrated that combination UCDA/dexamethasone treatment induced p300-related interactions between HNF1 and glucocorticoid receptor on the AE2 alternate promoter. Our data provide a potential molecular explanation for the beneficial effects of the combination of UDCA and glucocorticoids in PBC patients with inadequate response to UDCA monotherapy.

Enterohepatic cycling of bilirubin as a cause of 'black' pigment gallstones in adult life

In contrast to bile salts, which undergo a highly efficient enterohepatic circulation with multiple regulatory and physiologic functions, glucuronic acid conjugates of bilirubin are biliary excretory molecules that in health do not have a continuing biologic life. Intestinal absorptive cells are devoid of recapture transporters for bilirubin conjugates, and their large size and polarity prevent absorption by passive diffusion. However, unconjugated bilirubin, the beta-glucuronidase hydrolysis product of bilirubin glucuronides can be absorbed passively from any part of the small and large intestines. This can occur only if unconjugated bilirubin is kept in solution and does not undergo rapid bacterial reduction to form urobilinoids. Here we collect, and in some cases reinterpret, experimental and clinical evidence to show that in addition to the well-known occurrence in newborns, enterohepatic cycling of unconjugated bilirubin can reappear in adult life. This happens as a result of several common conditions, particularly associated with bile salt leakage from the small intestine, the most notable ileal dysfunction resulting from any medical or surgical cause. We propose that when present in excess, colonic bile salts solubilize unconjugated bilirubin, delay urobilinoid formation, prevent calcium complexing of unconjugated bilirubin and promote passive absorption of unconjugated bilirubin from the large intestine. Following uptake, reconjugation, and resecretion into bile, this source of 'hyperbilirubinbilia' may be the important pathophysiological risk factor for 'black' pigment gallstone formation in predisposed adult humans.

Review article: mechanisms of action and therapeutic applications of ursodeoxycholic acid in chronic liver diseases

Ursodeoxycholic acid (ursodiol) is a non-toxic, hydrophilic bile acid used to treat predominantly cholestatic liver disorders. Better understanding of the cellular and molecular mechanisms of action of ursodeoxycholic acid has helped to elucidate its cytoprotective, anti-apoptotic, immunomodulatory and choleretic effects. Ursodeoxycholic acid prolongs survival in primary biliary cirrhosis and it improves biochemical parameters of cholestasis in various other cholestatic disorders including primary sclerosing cholangitis, intrahepatic cholestasis of pregnancy, cystic fibrosis and total parenteral nutrition-induced cholestasis. However, a positive effect on survival remains to be established in these diseases. Ursodeoxycholic acid is of unproven efficacy in non-cholestatic disorders such as acute rejection after liver transplantation, non-alcoholic steatohepatitis, alcoholic liver disease and chronic viral hepatitis. This review outlines the present knowledge of the modes of action of ursodeoxycholic acid, and presents data from clinical trials on its use in chronic liver diseases.

Ursodeoxycholic acid in the treatment of liver diseases

Ursodeoxycholic acid is a dihydroxy bile acid with a rapidly expanding spectrum of usage in acute and chronic liver diseases. The various mechanisms of action of this hydrophilic bile acid include direct cytoprotection, detergent action on dysfunctional microtubules, immunomodulation and induction of hypercholeresis. Its efficacy in primary biliary cirrhosis and primary sclerosing cholangitis as an adjunct to medical therapy has been well established. Newer indications include its use in the management of chronic hepatitis, cirrhosis, post liver transplant rejection, graft-versus-host disease and acute viral hepatitis, where it not only relieves symptoms of cholestasis but also arrests ongoing hepatocyte necrosis.

Acute effect of ursodeoxycholic acid on gallbladder volume in healthy subjects

BACKGROUND

Although it has been shown that chronic administration of ursodeoxycholic acid increases gallbladder fasting and residual volume, it is unknown whether ursodeoxycholic acid exerts an acute effect on gallbladder volume. We therefore evaluated the effect of a single oral dose of ursodeoxycholic acid on gallbladder volume in healthy volunteers.

METHODS

After the volunteers had fasted overnight, gallbladder volume was measured sonographically every 15 min for 5 h. Following a 1-h control period group I (n = 8) received ursodeoxycholic acid (1000 mg) orally with 100 ml of water, whereas group II (n = 8) received 100 ml of water (placebo) only. Gallbladder volumes were calculated, applying the sum-of-cylinders method. Serum levels of ursodeoxycholic acid were determined by gas chromatography at 1-h intervals.

RESULTS

Gallbladder fasting volumes before ursodeoxycholic acid were similar in both groups (24.0 +/- 2.3 ml versus 25.4 +/- 3.3 ml; NS). After ingestion of ursodeoxycholic acid (group I) gallbladder volume increased rapidly, reaching 27.6 +/- 3.1 ml (p < 0.04) 1 h and 38.4 +/- 3.4 ml (p < 0.02) 4 h after ingestion of ursodeoxycholic acid. The individual gallbladder volumes after ingestion of ursodeoxycholic acid in group I increased to 146%-211% of pretreatment values. Ursodeoxycholic acid serum levels increased from 0.94 +/- 0.38 mumol/l to 10.51 +/- 1.36 mumol/l (p < 0.001) and correlated closely with gallbladder volumes (r = 0.80; p < 0.05). After ingestion of water only (group II) gallbladder volume decreased transiently from 15 min to 30 min after water intake and then remained at pretreatment values throughout the study period.

CONCLUSION

Administration of a single oral dose of ursodeoxycholic acid causes a rapid increase in gallbladder volume, which reaches 163 +/- 10% of pretreatment volume at 4 h and is closely correlated with ursodeoxycholic acid serum levels.

Bile acid conjugation in early stage cholestatic liver disease before and during treatment with ursodeoxycholic acid

The efficiency of bile acid conjugation before and during therapy with 600 mg/day of ursodeoxycholic acid was measured in seven adult patients with early chronic cholestatic liver disease (6 with primary biliary cirrhosis; 1 with primary sclerosing cholangitis). Duodenal bile samples were obtained by aspiration and the proportion of unconjugated bile acids was determined using lipophilic anion exchange chromatography to separate bile acid classes, followed by analysis of individual bile acids by gas chromatography-mass spectrometry. The proportion of conjugated bile acids was determined by high-performance liquid chromatography. Use of a (99m)Tc-HIDA recovery marker permitted the absolute mass of unconjugated bile acids in the gallbladder to be calculated. Unconjugated bile acids comprised 0.4% of total biliary bile acids before and 0.2% during ursodeoxycholic acid therapy, indicating highly efficient conjugation of bile acids. During therapy, percentage unconjugated ursodeoxycholic acid significantly increased from (mean +/- S.D.) 13 +/- 13% to 54 +/- 12%; P < 0.002. When the unconjugated and conjugated fractions of bile acids were compared, there was an enrichment in unconjugated fraction for cholic acid and ursodeoxycholic acid and a depletion for chenodeoxycholic acid both in basal condition and during ursodeoxycholic acid therapy, suggesting that hydrophilic bile acids were conjugated less efficiently. During therapy, the conjugation efficiency significantly increased for cholic acid and ursodeoxycholic acid. The pretreatment mass of total unconjugated bile acids in the gallbladder was (mean +/- S.D.) 4.4 +/- 3.2 mumol, and was not significantly changed by ursodeoxycholic acid therapy (6.2 +/- 3.5 mumol). However, ursodeoxycholic acid therapy caused a significant increase in the mass of unconjugated ursodeoxycholic acid. It is concluded that endogenous bile acids and exogenous ursodeoxycholic acid when given at the usual dose are efficiently conjugated in patients with early cholestatic liver disease. Despite showing increased biliary unconjugated ursodeoxycholic acid during its oral administration, our data do not lend support to the occurrence of hypercholeresis due to cholehepatic shunting of bile acids.

[Bile acids and their therapeutic use in children]

Bile acids are natural detergents and the end-products of cholesterol metabolism. Their functions are mostly digestive: induction of bile flow and solubilization of biliary and alimentary lipids. They circulate along the enterohepatic cycle, and probably also along a shorter route, the cholehepatic shunt. They are relatively hydrophobic and perpetuate or worsen the hepatic lesions when their excretion is impaired in cholestasis, because of their affinity for biological membranes. Their functions depend on their relative hydrophilicity and ionization, ie on their structure and state of conjugation. They have an immunosuppressive effect in vivo and in vitro. Ursodeoxycholic acid (UDC) is a hydrophilic bile acid used in chronic cholestatic diseases. Biological improvement has been proven in autoimmune cholangiopathies in adults, and cystic fibrosis-associated liver disease in children. Clinical studies are on the way for other indications. It is still too early to evaluate the long-term clinical benefits, eg the reduction in needs for liver transplantation. UDC acid may induce a bicarbonate-rich hypercholeresis through the cholehepatic shunt, that would explain its efficacy in cystic fibrosis. In disorders of bile acid synthesis or transport, it could shunt the enzymatic block, or reestablish the bile flow through its osmotic effect. Like other bile acids it interacts with membranes, and is thought to stabilize them. In chronic cholestasis it would protect the membranes against the adverse effect of non-excreted endogenous bile acids. This interaction can also explain its immunosuppressive effect, through non-specific inhibition of transmission at the cell surface. That would explain the preferential clinical efficacy of UDC in autoimmune cholestasis, and stimulate its evaluation in "immunological" indications, such as liver transplantation and hepatic graft versus host disease.

Hypercalcemia decreases bile flow and increases biliary calcium in the prairie dog

BACKGROUND

Biliary calcium is known to play an important role in the pathogenesis of gallstones. Calcium salts are present in all pigment gallstones and are also present in the core of most, if not all, cholesterol gallstones.

METHODS

The effects of acute hypercalcemia on bile flow and biliary calcium secretion were examined in 22 prairie dogs during intravenous taurocholate infusion (0, 1.0, 2.25, and 4.5 mumol/kg/min).

RESULTS

Bile flow was linearly correlated with bile acid output in both control (y = 7.62x + 13.5, r = 0.98) and hypercalcemic (y = 7.00x + 10.4, r = 0.96) animals. At lower bile acid outputs (< 3.0 mumol/kg/min), biliary ionized calcium output per increment bile acid output was significantly increased in hypercalcemic animals (0.016 versus 0.011 mumol Ca++ mumol taurocholate, p < 0.001). Bile ionized calcium concentrations approximated Gibbs-Donnan predicted values only at low bile flow rate.

CONCLUSIONS

Hypercalcemia decreases bile flow and increases biliary ionized calcium concentration in the prairie dog. These effects favor the precipitation of calcium salts in bile.

Effect of acute bile acid pool depletion on total and ionized calcium concentrations in human bile

Although calcium salts are important components of gallstones, there are few data on the total and ionized calcium content of human bile. Therefore, in 14 fasting T-tube patients studied 7-11 days after cholecystectomy, we measured bile flow, bile acid [BA], total [CaTOT] and free ionized [Ca++] calcium concentrations, in 20-30 min bile collections during acute BA pool depletion induced by 6-8 h of continuous bile drainage. During washout of the BA pool there were parallel falls in bile flow, BA output and total calcium output (correlation coefficients ranging from 0.59 to 0.99; P < 0.02-0.001). In 12 of the 14 patients, [CaTOT] also fell (from 1.84 +/- 0.29 to 1.32 +/- 0.34 mmol L-1) in parallel with [BA] (from 34.0 +/- 14.0 to 8.2 +/- 8.0 mmol L-1; r = 0.75-0.98; P < 0.005). In contrast, biliary [Ca++] remained virtually unchanged. These data suggest that the BAs are linked to the bound, rather than to the free, ionized, fraction of biliary calcium, which is consistent with in vivo calcium binding by BAs. A model is proposed in which BA-induced biliary calcium secretion results from (i) bile acid-induced water flow via solvent drag; and (ii) calcium binding in the bile canaliculus by bile acids, which induces paracellular diffusion of Ca++, thereby maintaining [Ca++] independent of [BA].

Changes in serum calcium levels influence biliary calcium levels in humans

BACKGROUND/AIMS

There are few data on the influence of serum calcium on biliary total and ionized calcium levels in humans. The aims of the study were to increase serum calcium levels short-term by intravenous calcium infusion and study the resultant changes in total and ionized calcium concentrations ([CaTOT] and [Ca2+]) in T-tube bile.

METHODS

Serum and biliary total and ionized calcium concentrations were measured over an 8-hour period in 7 postcholecystectomy patients with T tubes before, during, and after a 4-hour intravenous infusion of 10% calcium gluconate.

RESULTS

During the infusion, serum [CaTOT] increased from 2.08 +/- 0.14 mmol/L (mean +/- SD) to 3.18 +/- 0.33 mmol/L, and serum [Ca2+] increased from 1.13 +/- 0.13 mmol/L to 1.68 +/- 0.13 mmol/L. After a 20-40-minute time lag, there were corresponding increases in biliary [CaTOT] from 1.90 +/- 0.45 mmol/L to 2.80 +/- 0.52 mmol/L and in biliary [Ca2+] from 0.70 +/- 0.11 mmol/L to 1.19 +/- 0.16 mmol/L. When the data were pooled, serum [Ca2+] showed significant correlations with both biliary [CaTOT] (n = 128; r = 0.56; P < 0.001) and biliary [Ca2+] (n = 128; r = 0.64; P < 0.001).

CONCLUSIONS

These results support the hypothesis that the biliary tree is freely permeable to calcium ions and that serum calcium level is one determinant of biliary calcium concentration. Our data may also explain the observation that patients with hypercalcemia are reported to have a greater than normal prevalence of calcified gallstones.

Pharmacology of ursodeoxycholic acid, an enterohepatic drug

The pharmacokinetics, metabolism, as well as the pharmacodynamic actions of ursodeoxycholic acid are reviewed and related to its physicochemical properties. Ursodeoxycholic acid is absorbed incompletely because of its low aqueous solubility. After absorption, it is conjugated with glycine or taurine and circulates with the endogenous bile acids. At usual doses (8-10 mg/kg/day), the pool of ursodeoxycholyl conjugates constitutes 30-60% of circulating bile acids. Ursodeoxycholic acid is metabolized by intestinal bacteriae to lithocholic acid which does not accumulate in the circulating bile acids because of efficient hepatic sulfation. Administration of ursodeoxycholic acid causes decreased cholesterol absorption, increased bile acid biosynthesis, and decreased biliary cholesterol secretion. Ursodeoxycholic acid is a choleretic agent, as all bile acids, but differs from other dihydroxy-bile acids in being non-cytotoxic because it has less affinity for membranes, and when present at micellar concentrations does not solubilize membranes. Chronic administration of ursodeoxycholic acid appears to increase canalicular transport.

Ursodeoxycholic acid for treatment of primary sclerosing cholangitis: a placebo-controlled trial

The efficacy and safety of ursodeoxycholic acid for the treatment of primary sclerosing cholangitis were evaluated in a prospective, randomized, double-blind, placebo-controlled trial. Fourteen patients with primary sclerosing cholangitis documented by cholestatic serum enzyme pattern, liver histological appearance and endoscopic retrograde cholangiography were included in the trial. Six patients received ursodeoxycholic acid (13 to 15 mg/kg body wt/day), and eight patients received placebo. Two patients had to be withdrawn from the study, one because of UDCA-related diarrhea and the other because of worsening of the disease during placebo treatment. Patients in the ursodeoxycholic acid group improved significantly during 1 yr of treatment with respect to serum levels of bilirubin (median = -50%), alkaline phosphatase (median = -67%), gamma-glutamyltransferase (median = -53%), AST (median = -54%) and ALT (median = -36%) compared with the placebo group, but not with respect to serum levels of hydrophobic bile acids. During ursodeoxycholic acid treatment, histopathological features also improved significantly, as evaluated by multiparametric score. Expression of human leukocyte antigen class I molecules appeared to be markedly reduced on liver cells after ursodeoxycholic acid treatment. We conclude that ursodeoxycholic acid is beneficial in reducing disease activity in patients with primary sclerosing cholangitis.

Bile composition, microspheroliths, antinucleating activity, and gallstone calcification

This study examined if abnormalities in bile composition and antinucleating activity are associated with gallstone calcification. Nineteen controls without gallbladder disease and 42 patients with cholesterol stones were studied. Bile was obtained at surgery and analyzed for pH and PCO2, ionized calcium, and total calcium. The pH and carbonate concentrations of gallbladder bile were significantly higher in patients with calcified stones than in patients with noncalcified stones and in controls, resulting in significantly higher levels of the ion product in patients with calcified gallstones. Microspheroliths of calcium carbonate, seen on microscopic examination of bile, predicted stone calcification with a sensitivity of 86%, a specificity of 86%, and a predictive value of 86%. Bile from control subjects completely inhibited precipitation of calcium carbonate from a supersaturated solution, whereas bile from subjects with calcified and noncalcified gallstones did not. It is concluded that gallstone calcification is related to elevated bile pH and carbonate concentrations, resulting in an elevated ion production of calcium carbonate in gallbladder bile. In addition, bile from subjects with calcified and noncalcified gallstones lacks antinucleating activity for calcium carbonate.

Spontaneously diabetic biobreeding rats and impairment of bile acid-independent bile flow and increased biliary bilirubin, calcium and lipid secretion

Chemically induced diabetes has been reported to induce profound changes in bile formation, but possible toxic effects of the streptozotocin or alloxan used cannot be excluded totally. This study was undertaken to evaluate biliary function in spontaneously diabetic female biobreeding rats with a diabetes duration of 2 wk and compare them with nondiabetic littermates. Diabetic animals evidenced glycosuria, hyperglycemia and hypoinsulinemia. Biliary concentration and secretion of bile acids, cholesterol and phospholipids were significantly increased, with no enhancement in the lithogenic index of bile. Bile flow and the biliary secretion of sodium, potassium, chloride and bicarbonate were significantly reduced despite the increased bile acid secretion. The cholestatic condition was confirmed by an increased serum concentration of bile acids and a higher activity in serum of the alkaline phosphatase liver isoenzyme. Biliary calcium concentration increased without any change in its serum concentration. A linear relationship was observed between biliary calcium and bile acid secretion. Serum concentration of unconjugated and of conjugated bilirubin was increased 1.6-fold and 8-fold, respectively, with a 1.5-fold enhanced biliary secretion of bilirubins despite the cholestasis; this points to an enhanced bilirubin production. An increased proportion of conjugated bilirubin was found in serum together with an enhanced bilirubin diconjugate/monoconjugate ratio in bile. A higher UDP-glucuronyltransferase activity and a delayed transit of bilirubin could account for these effects. Administration of insulin to diabetic animals tended to reverse the above reported changes. The spontaneously diabetic biobreeding rat thus represents a model of bile acid-independent cholestasis with enhanced biliary bile acid and calcium secretion and with presumably an enhanced bilirubin production.

Scintigraphic documentation of an improvement in hepatobiliary excretory function after treatment with ursodeoxycholic acid in patients with cystic fibrosis and associated liver disease

We have previously documented that ursodeoxycholic acid exerts a beneficial effect on liver function and bile acid metabolism in patients with cystic fibrosis. We hypothesized that the mechanism of action may be related in part to the choleretic properties of the administered bile acid. We therefore compared hepatobiliary scintigraphic images obtained before and 1 yr after initiation of ursodeoxycholic acid therapy to document an improvement in bile flow in 13 patients with cystic fibrosis and hepatobiliary involvement. Before therapy, hepatobiliary scintigraphy documented biliary stasis with retention of the isotope in intrahepatic and extrahepatic bile ducts in nine patients; during therapy, duct dilatation decreased substantially in eight patients, with decreased intrahepatic retention and more rapid biliary outflow of the tracer. The time of appearance of isotope in the intestine decreased (from a mean of 36.9 +/- 17.8 min to 18.8 +/- 9.0 min; p less than 0.01) in all patients in whom it had been abnormal, and the half-time of hepatic washout decreased from a mean of 35 +/- 20.7 min to 26 +/- 15.6 min (p less than 0.05). During ursodeoxycholic acid administration enrichment of bile was achieved, with the mean ursodeoxycholic acid percent composition increasing from 5.8% +/- 2.9% to 35.7% +/- 8.5%. Ursodeoxycholic acid became the predominant bile acid in serum. Liver function improved in all 10 of the patients with abnormal values at baseline. We conclude that hepatobiliary scintigraphy is of value in monitoring the therapeutic responses of cystic fibrosis patients with liver disease to ursodeoxycholic acid therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Recovery of bile secretion following orthotopic liver transplantation

Recovery of hepatic function following orthotopic liver transplantation includes the ability to produce 'adequate' bile. What constitutes adequate bile flow, however, has not previously been defined. The present study was undertaken to characterize biliary water and electrolyte secretion following hepatic transplantation. Bile was sampled from nine liver transplant recipients for 15-25 consecutive days during chronic t-tube biliary drainage. Liver biopsies and t-tube cholangiograms were unremarkable in all patients. During the first post-operative day mean bile flow, bile salt concentration, [BS], and bile salt output (BSO) were 60.0 microliters/min, 6.8 mM and 0.41 mumol/min, respectively. [BS] increased over days 1-5 and then plateaued at 12.2 mM over days 6-25 post-transplant. BSO and bile flow increased over days 1-12 before achieving steady-state values of 4.52 mumol/min and 334.7 microliters/min, respectively. In each patient bile flow increased linearly with increasing BSO. Choleretic index (CI), varied from 36.9-77.1 microliters/mumol (mean: 50.7 +/- 8.8). The y-intercept for this relationship ranged from 52.4-156.9 microliters/min (mean: 95.9 +/- 81.8). Only primary bile salts (82% cholate and 17% chenodeoxycholate), were observed in the bile of each patient. Biliary electrolyte concentrations were similar to that observed in plasma. Each was relatively unaffected by changes in bile flow and BSO. Electrolyte outputs increased linearly with respect to both BSO and bile flow. We conclude that recovery of bile secretion following orthotopic liver transplantation occurs gradually over a 10-12 day period and is strongly dependent upon bile salt secretion.

Nucleation time, cholesterol saturation index, and biliary bile acid pattern. A comparison in responders and nonresponders to systemic litholysis with bile acids

In a 24-month trial of a combination therapy with ursodeoxycholic acid and chenodeoxycholic acid complete dissolution of radiolucent gallstones was achieved in 15 of 55 patients (27.3%). A decrease of stone volume of greater than 35% was achieved in a further 28 patients (50.9%). In 12 patients (21.8%) inadequate compliance (3.6%), a nonfunctioning gallbladder (3.6%), absence of size decrease (10.9%), or acute cholecystitis (3.6%) required interruption of therapy. Determination of the cholesterol saturation index (CSI) did not facilitate patient selection, nor was there a statistically significant difference between responders and nonresponders to dissolution therapy. In the course of treatment the average CSI showed a statistically significant decrease from 1.54 +/- 0.12 to 0.82 +/- 0.06 (p less than 0.001). Patients in whom complete dissolution was achieved and those in whom no improvement was observed differed significantly in nucleation time (4.7 +/- 0.8 versus 15.0 +/- 2.2 days; p less than 0.001) and initial gallstone volume (274 +/- 78 versus 1045 +/- 180 mm3). The nucleation time increased statistically significantly during the therapy in the successfully treated group. The percentages of glycocholic acid (8.1 +/- 1.13 versus 4.1 +/- 0.55%; p less than 0.01), taurocholic acid (2.2 +/- 0.45 versus 0.8 +/- 0.23%; p less than 0.05), and glycodeoxycholic acid (4.9 +/- 0.70 versus 1.4 +/- 0.37%; p less than 0.001) were statistically significantly different after the treatment. There were no statistically significant differences between patients with complete and incomplete stone dissolution with regard to age, mean body weight, or laboratory variables.

The effects of synthetic human secretin on calcium carbonate solubility in human bile

This study sought to determine the effects of synthetic human secretin on ionized calcium and carbonate concentrations in human hepatic bile. Five patients with a nasobiliary drain in the right hepatic duct were studied. Three basal samples of bile were collected, each over a 15-minute period. Synthetic human secretin was then infused IV at 0.05 micrograms.kg-1.h-1 for 45 minutes followed by 0.5 micrograms.kg-1.h-1 for 45 minutes. Bile was sampled over 15-minute periods. To document return to baseline conditions, two further samples of bile were obtained over 15-minute periods 2 hours after the infusion was terminated. Bile acid concentration was determined by an enzymatic method; pH and PCO2 were measured with an automated analyzer. Total calcium was determined by inductively coupled plasma emission spectrometry and ionized calcium by an ion-specific electrode. Bicarbonate and carbonate concentrations were calculated using Henry's law and the Henderson-Hasselbalch equation. The fraction of bile sampled by the catheter was determined by Indocyanin Green recovery at the end of the experiment. Secretin caused an increase in bile flow and bicarbonate output. Bicarbonate concentrations increased from 26 +/- 3 mmol/L to 41 +/- 3 mmol/L (P less than 0.05), and chloride concentrations decreased. Mean bile acid concentrations declined significantly from 14.6 +/- 2 mmol/L to 4.7 +/- 1 mmol/L (P less than 0.05). Ionized calcium concentrations decreased from 0.7 +/- 0.005 mmol/L to 0.5 +/- 0.02 mmol/L (P less than 0.05) while pH increased significantly from 7.44 +/- 0.06 to 7.6 +/- 0.04 (P less than 0.05). Carbonate concentrations increased significantly from 0.15 +/- 0.02 mmol/L to 0.26 +/- 0.03 mmol/L, and the ion product for calcium carbonate increased significantly from 0.099 +/- 0.002 (mmol/L)2 to 0.135 +/- 0.015 (mmol/L)2 (P less than 0.05). Synthetic human secretin augments the ion product of calcium and carbonate in human hepatic bile, increasing the tendency for calcium carbonate precipitation.