A radioimmunoassay for lithocholic acid conjugates in human serum and liver tissue

Enzyme-linked immunosorbent assay (ELISA) for the anthropogenic marker isolithocholic acid in water

Bile acids are promising chemical markers to assess the pollution of water samples with fecal material. This study describes the optimization and validation of a direct competitive enzyme-linked immunosorbent assay for the bile acid isolithocholic acid (ILA). The quantification range of the optimized assay was between 0.09 and 15 μg/L. The assay was applied to environmental water samples. Most studies until now were focused on bile acid fractions in the particulate phase of water samples. In order to avoid tedious sample preparation, we undertook to evaluate the dynamics and significance of ILA levels in the aqueous phase. Very low concentrations in tap and surface water samples made a pre-concentration step necessary for this matrix as well as for wastewater treatment plant (WWTP) effluent. Mean recoveries for spiked water samples were between 97% and 109% for tap water and WWTP influent samples and between 102% and 136% for WWTP effluent samples. 90th percentiles of intra-plate and inter-plate coefficients of variation were below 10% for influents and below 20% for effluents and surface water. ILA concentrations were quantified in the range of 33-72 μg/L in influent, 21-49 ng/L in effluent and 18-48 ng/L in surface water samples. During wastewater treatment the ILA levels were reduced by more than 99%. ILA concentrations of influents determined by ELISA and LC-MS/MS were in good agreement. However, findings in LC-ELISA experiments suggest that the true ILA levels in concentrated samples are lower due to interfering effects of matrix compounds and/or cross-reactants. Yet, the ELISA will be a valuable tool for the performance check and comparison of WWTPs and the localization of fecal matter input into surface waters.

Thermodynamic features of bile salt-human serum albumin interaction

Interaction with human serum albumin is responsible for important aspects of the physiological behaviour of bile salts, although this factor has not been adequately examined. The nature of the binding is investigated here by means of thermodynamic parameters determined by equilibrium dialysis and microcalorimetric measurements. The positive enthalpy and entropy values obtained indicate the presence of a poorly specific hydrophobic bonding.

Effect of nuclear hydroxy substituents on aqueous solubility and acidic strength of bile acids

The aqueous solubility and thermodynamic dissociation constants of a representative series of bile acids with varying numbers and configuration of nuclear hydroxyl substituents were determined. The pKa values were calculated by extrapolating pKa' values determined in solutions of aqueous methanol of different mole fractions at 25 degrees C. All bile acids had the same acidic strength in water, indicating that the pattern of hydroxyl nuclear substituents does not affect the acidic strength probably because of the distance between the hydroxyl and ionizing groups. In contrast, aqueous solubility was dependent on the number, position and orientation of the hydroxyl groups. The solubility values ranged from 5 X 10(-8) M (0.05 microM) for 3 alpha-hydroxy-5 beta-cholanoic acid (lithocholic acid) to 1.67 X 10(-3) M (1,670 microM) for 3 alpha,7 beta,12 alpha-trihydroxy-5 beta-cholanoic acid (ursocholic acid). The hydroxy groups notably affect solubility by forming hydrogen bonds with water but also by reducing, according to their orientation, hydrophobicity of the steroid nucleus.

Diagnostic effectiveness of serum bile acids in liver diseases as evaluated by multivariate statistical methods

The aims of this study were to determine the diagnostic effectiveness of fasting and postprandial serum bile acid determinations in liver diseases, and to compare results with those of conventional liver function tests. In 322 patients with biopsy-proved liver disease and 93 healthy subjects, fasting and postprandial (2 hr) serum levels of cholic, chenodeoxycholic, and lithocholic acid conjugates and conventional liver function tests were evaluated. Data were subjected to variance and discriminant and factor analyses. Fasting serum bile acids were higher in patients when compared to controls and were significantly higher in severe than in mild liver diseases. Determination of cholic plus lithocholic acid provided the highest discrimination capacity. The percent of correct allocation was 75.4% for conventional liver function tests, 70.1% for fasting serum bile acids and increased to 79.6% when liver function tests plus serum bile acids were considered. Postprandial percentages were always lower than fasting. Factor analysis identified two factors possibly related to cytolysis and protein synthesis. The serum bile acid concentrations highly correlated with both factors. We conclude that serum bile acid determinations increase the diagnostic and discriminant capacities of liver function tests and are more sensitive and discriminant when obtained in fasting than postprandially.

Ursodeoxycholic acid vs. chenodeoxycholic acid as cholesterol gallstone-dissolving agents: a comparative randomized study

Cholesterol gallstones are dissolved in man by chenodeoxycholic acid (CDCA) and ursodeoxycholic acid (UDCA). To test the comparative efficacy of these two cholelitholytic bile acids, 223 gallstones patients were randomly treated with either UDCA or CDCA at two different doses: 7 to 8 mg per kg per day and 14 to 15 mg per kg per day. Efficacy and factors influencing dissolution (dose, size of the stones, and time) were evaluated after 3, 6, and 12 months of treatment. UDCA was significantly more efficacious than was CDCA after 3 and 6 months of treatment, whereas after 12 months, no significant differences were observed. UDCA was equally effective at high and low doses, both on small and large stones. CDCA was significantly more effective at high doses and on small stones. Seventy-four per cent of the total dissolutions with UDCA and 42% with CDCA occurred within the first 6 months of treatment. Diarrhea and hypertransaminasemia occurred only in the CDCA-treated patients. We conclude that UDCA seems to be the bile acid of choice in dissolving cholesterol gallstones.