Microanalysis of free and conjugated bile acids by thin-layer chromatography and in situ spectrofluorimetry

Isolation and determination of bile acids

In this article, the methods of isolation and determination of bile acids are reviewed. Methods for separation of bile acids from cattle and pig bile are given in detail. Isolation of a mixture of cholic acid and deoxycholic acids from cattle bile and their subsequent purification are described. The isolation and purification of hyodeoxycholic acid and other components of pig bile are also included. Methods for the determination of bile acids in various biological samples are reviewed, including enzyme assays, radioimmunoassay, enzyme immunoassay and chromatographic methods. Among chromatographic methods, separation and determination of bile acids by thin-layer chromatography, gas chromatography and high performance liquid chromatography are reviewed. Particular attention is given to the use of high performance liquid chromatography since this has recently been the most commonly applied method for the separation and determination of bile acids.

Expression of cholesterol 7alpha-hydroxylase restores bile acid synthesis in McArdle RH7777 cells

Bile acid synthesis involves several enzymes and occurs only in liver cells. The first and rate-determining step is catalyzed by cholesterol 7alpha-hydroxylase (cyp7a). McArdle RH7777 hepatoma cells do not synthesize bile acids and do not express the cyp7a gene. A synthetic cyp7a gene was stably expressed in this cell line to determine if restoration of cyp7a activity is sufficient to reconstitute the bile acid synthetic pathway. The transfected cells contained the recombinant cyp7a mRNA and the corresponding protein. Microsomes from recombinant cells converted cholesterol into 7alpha-hydroxycholesterol, indicating that the recombinant enzyme was active. Radiolabeled bile acids, originated from exogenously supplied radiolabeled cholesterol, were detected in the culture medium of recombinant cells. Thus, expression of cyp7a is sufficient in restoring bile acid synthesis in McArdle RH7777 cells. The results also show that the additional complement of enzymatic activities required to convert cholesterol into bile acids has remained active in this cell line.

A coupled assay for bile acid:CoA ligase

A new assay for the enzyme bile acid:CoA ligase is presented. The new assay is designed to supplant the existing radiometric assays which require radiolabeled bile acids. The new assay couples the formation of bile acid-CoA to its glycination in a reaction catalyzed by bile acid-CoA:glycine N-acyltransferase. The coupling reaction utilizes [14C]glycine and the bile acid-CoA is quantitatively converted to [14C]glycobile acid. The [14C]glycobile acid is isolated by solvent extraction and quantitated by liquid scintillation counting. The method is shown to be accurate, highly sensitive, and applicable to a wide variety of bile acids.

Evaluation of duodenogastric reflux in gallstone disease before and after simple cholecystectomy

Duodenogastric reflux (DGR) has been suggested as an etiopathogenic factor in gastric disease in patients with gallstones. We evaluated the DGR levels in 15 patients before and after simple cholecystectomy for gallstones and compared the results with those of 15 healthy subjects. Gastric juice was obtained by continuous nasogastric suction for 24 hours. The bile acids (BA) present in the samples were quantified by thin-layer chromatography and in situ spectrofluorometry. The mean BA concentration for the control subjects was 2.25 mumol reflux/hour, whereas the mean value for the 15 patients with cholelithiasis was 8.86 mumol reflux/hour before cholecystectomy and 24.55 mumol reflux/hour after cholecystectomy. Five patients did not have detectable BA in the gastric juice in both analyses; the remaining 10 patients showed a significant increase in the BA after surgery. From these data, we conclude that gallstone disease is not always accompanied by an increased DGR. However, in patients in whom DGR is present, its level is higher than in control subjects and increases significantly after cholecystectomy. This is probably due to the greater amount of bile in the duodenum that may reflux through an incompetent pyloric channel.

Bile reflux in postoperative alkaline reflux gastritis

This study evaluates enterogastric reflux (EGR) levels in patients with and without symptoms of postoperative alkaline reflux gastritis (PARG) after gastric surgery. The bile acids (BA) present in the gastric juice were quantified by thin-layer chromatography and spectrofluorometry. The mean BA concentration for controls was 2.25 mumol reflux/hour, for 15 asymptomatic patients 47.94 and for 15 patients with symptoms of PARG 125.79. After biliary diversion by a Roux-en-Y anastomosis in the latter, their BA in 13 of these patients after surgery, and relapsed in only one during a 4-year follow-up. The remaining two patients had the lowest preoperative BA levels in this group. These results indicate that EGR is increased after gastric surgery more markedly indicated that EGR is increased after gastric surgery more markedly in patients with symptoms of PARG, and that patients who have high levels of EGR (more than 80 mumol BA reflux/hour) clearly benefit from biliary diversion.

New and versatile method for the determination of faecal bile acids by thin-layer chromatography with direct scanning fluorimetry

A sensitive, versatile and precise method for quantitative analysis of individual faecal bile acids in humans by thin-layer chromatography with direct scanning fluorimetry is described. The method enables convenient quantitative measurements of faecal bile acids in larger series of samples for routine applications in gastroenterology. The overall coefficient of variation (including stool preparation and extraction) for the five predominant bile acids of human stool specimens (cholic acid, chenodeoxycholic acid, deoxycholic acid, lithocholic acid and ursodeoxycholic acid) was 3.4-4.9%. Recoveries of free bile acids added to the faeces ranged from 91% to 106%. An excellent and linear correlation between this method and fused-silica column gas chromatography with temperature programming was established (r = 0.91-0.99). In clinical practice this thin-layer chromatographic method constitutes a reliable, simple and time-saving alternative to gas chromatography.

Planar chromatographic techniques in biomedicine: current status

In planar chromatography (PLC), the solvent flows through a layer either by means of capillary forces [conventional thin-layer chromatography (TLC)] or by a forced-flow system (over-pressured layer chromatography). Phases and instrumentation currently available are briefly examined. The main applications in biomedicine are reviewed. Although silica gel TLC plates still predominate, interest in other phases is increasing. Unique detection features such as immunostaining are emphasized. Although gas chromatography and high-performance liquid chromatography have superseded TLC in the analysis of carbohydrates, amino acids and indole derivatives, interest in PLC continues to be high in lipid analysis.

Bone metabolism in rheumatoid arthritis compared with postmenopausal osteoporosis

Calcium and bone metabolism in 29 rheumatoid arthritis (RA) patients were compared with those in 27 postmenopausal osteoporotic patients. Signs of vitamin D deficiency were found in 20 RA patients, including 12 who took recommended amounts of vitamin D in their diets and were exposed to sufficient sunlight, and in none of the osteoporotic patients. There were no signs of malabsorption. In six out of 15 patients we found increased liver enzyme activity, which may have a role in vitamin D metabolism. We propose the influence of non-steroidal anti-inflammatory drugs (NSAIDs) on vitamin D metabolism in the liver as a possible explanation.