Glucuronic acid conjugates

The methods of assay in body fluids of 1-beta-alkyl, 1-beta-phenyl and 1-beta-acyl glucuronic acids ("glucuronide conjugates") have been reviewed. Most of the 78 references cited (from the literature of the period 1990-1997) concern the glucuronide conjugates of drug metabolites, and these have been considered, for reasons of accessibility, within sections of individual drug classes such as analgesics, anti-cancer agents and opioids. Other glucuronide conjugates are considered under "miscellaneous compounds". A few gas chromatography and capillary electrophoresis methods are described, but the major technique of assay (62 citations) is reversed-phase high-performance liquid chromatography.     

Quantitative estimations of the contribution of different bile acid pathways to total bile acid synthesis in the rat

BACKGROUND & AIMS: Cholesterol degradation to bile acids occurs via "classic" or "alternative" bile acid biosynthetic pathways. The aim of this study was to assess the contributions of these two pathways to total bile acid synthesis in vivo. METHODS: Rats with biliary fistulas were infused with squalestatin for 24 and 48 hours; specific activities of cholesterol 7 alpha-hydroxylase (C7 alpha H) and sterol 27-hydroxylase (S27H) and rates of bile acid synthesis were determined. RESULTS: Continuous squalestatin infusion (15 micrograms/h) decreased C7 alpha H specific activities to 4% and 12% of paired biliary fistula controls at 24 and 48 hours, respectively (P < 0.05) without any changes in S27H specific activities (82% and 95% of controls). At 24 hours, bile acid synthesis decreased to 43% (P < 0.05) but returned to 87% at 48 hours (P = NS). Cholic acid synthesis decreased at 24 hours but returned to control levels at 48 hours. Similar changes in C7 alpha H, S27H, and bile acid synthesis were observed in primary rat hepatocytes after addition of squalestatin (1.0 mumol/L). CONCLUSIONS: In the face of persistent suppression of C7 alpha H and the classic pathway, an alternative pathway becomes a main pathway of bile acid synthesis capable of generating cholic and chenodeoxycholic acids. The observed induction of bile acid synthesis via an alternative pathway or pathways represents an important mechanism for maintenance of cholesterol homeostasis in the rat.     

Effect of bile duct ligation on bile acid metabolism in rats

The effect of bile duct ligation on the quantitative and qualitative changes of bile acids in serum, liver, urine, and feces, and the concentration of cholesterol and phospholipids in serum and liver were examined in male rats. The concentration of bile acids in serum increased over 100-fold on day 5 but was lower than the 5-day level on days 10 and 15. The concentration in the liver also increased about 10-fold. beta-Muricholic acid predominantly increased but the secondary bile acids, deoxycholic acid and hyodeoxycholic acid, decreased. The urinary excretion of bile acids increased to about 40 mg/day per rat on the first day of bile duct ligation but this increase was reduced on day 2 to about half and remained at that level until day 24. These values exceeded that of fecal bile acids, 12 mg/day per rat, before bile duct ligation. The amount of bile acid sulfates in the urine was as low as 1% of the total. The urinary non-sulfated bile acids consisted mainly of beta-muricholic acid (60%) and cholic acid (20%), while the sulfates contained a considerable amount of unidentified acidic substances (40%) in addition to cholic acid and beta-muricholic acid. The concentration of cholesterol and phospholipids in serum markedly increased on day 5 but declined gradually thereafter. The liver cholesterol concentration did not change but the phospholipid concentration decreased. Fecal sterols did not change in both the total amount and composition. These data indicated that daily synthesis of bile acids, especially beta-muricholic acid, was accelerated in bile duct-ligated rats.     

Developmental pattern of bile acid metabolism as revealed by bile acid analysis of meconium

The developmental metabolism of bile acids can be partly studied by the analysis of bile acid patterns in meconium. Employing modern analytical techniques, it has been found that besides the main bile acids of humans (cholic, chenodexoycholic, deoxycholic, and lithocholic acids) several "atypical" bile acids occur in meconium. It is unlikely that these "atypical+ bile acids are derived from materno--fetal transfer, and they therefore probably reflect a special fetal bile acid metabolism. Hydroxylations at positions 1 and 6 of the steroid skeleton are regularly encountered. These hydroxylations, as well as the occurrence of 3 beta-hydroxy-delta 5 compounds and of bile acids of the 5 alpha series, suggest that fetal bile acid synthesis differs markedly from that of the adult. These observations are of interest in relation to the origin of unusual bile acids found in the cholestatic condition of the adult. It appears that a resurgence of the fetal biosynthetic patterns takes place under the conditions of cholestatic liver disease.     

Developmental pattern of 3-oxo-delta 4 bile acids in neonatal bile acid metabolism

AIMS: To investigate whether a fetal pathway of bile acid synthesis persists in neonates and infants. METHODS: 3-oxo-delta 4 bile acids were determined qualitatively and quantitatively in the urine, meconium, and faeces of healthy neonates and infants, using gas chromatography-mass spectrometry. RESULTS: The mean percentage of 3-oxo-delta 4 bile acids in total bile acids in urine at birth was significantly higher than that at 3 or 7 days, and at 1 or 3 months of age. The concentration of this component in meconium was significantly higher than that in faeces at 7 days and at 1 or 3 months of age. CONCLUSIONS: The presence of large amounts of urinary 3-oxo-delta 4 bile acids may indicate immaturity in the activity of hepatic 3-oxo-delta 4-steroid 5 beta-reductase in the first week of postnatal life. Large amounts of this component in meconium may be due to the ingestion of amniotic fluid by the fetus during pregnancy.     

Regulation of classic and alternative bile acid synthesis in hypercholesterolemic rabbits: effects of cholesterol feeding and bile acid depletion

The effect of cholesterol feeding (3 g/day) on bile acid synthesis was examined in 10 New Zealand white rabbits (NZW), 8 Watanabe heterozygous and 10 homozygous rabbits with partial and complete deficiencies of LDL receptors. After 10 days of cholesterol feeding, bile fistulas were constructed and bile acid pool sizes were measured. Cholesterol feeding increased plasma and hepatic cholesterol levels in all rabbit groups. Baseline bile acid pool sizes were smaller (P < 0.01) in heterozygotes (139 +/- 3 mg) and homozygotes (124 +/- 30 mg) than NZW rabbits (254 +/- 44 mg). After feeding cholesterol, bile acid pool sizes doubled with increased cholic acid synthesis in NZW and, to a lesser extent, in Watanabe heterozygous rabbits but not in homozygotes. Baseline cholesterol 7alpha-hydroxylase activity in NZW and heterozygotes declined 69% and 53% (P < 0.001), respectively, after cholesterol feeding. Sterol 27-hydroxylase activity reflecting alternative bile acid synthesis increased 66% (P < 0.01) in NZW and 37% in Watanabe heterozygotes but not in homozygotes after feeding cholesterol. Bile fistula drainage stimulated cholesterol 7alpha-hydroxylase activity but not sterol 27-hydroxylase activity in all three rabbit groups. These results demonstrated that dietary cholesterol increased hepatic sterol 27-hydroxylase activity and alternative bile acid synthesis to expand the bile acid pool and inhibited cholesterol 7alpha-hydroxylase in NZW and in Watanabe heterozygous rabbits but not in homozygotes with absent hepatic LDL receptor function. Thus, in rabbits, sterol 27-hydroxylase is up-regulated by the increased hepatic cholesterol that enters the liver via LDL receptors whereas cholesterol 7alpha-hydroxylase is controlled by the circulating hepatic bile acid flux.     

Evaluation of total serum bile acids concentration and bile acid profiles in healthy cats after oral administration of ursodeoxycholic acid

Ursodeoxycholic acid (UDCA; 10 mg/kg of body weight) was administered orally to 5 healthy cats for 3 months. Signs of illness were not apparent in any cat during treatment with UDCA. Results of monthly CBC, serum biochemical analysis, and urinalysis were unchanged during drug administration. There was a decrease in serum cholesterol concentration in 4 cats. Total postprandial serum bile acids (PPSBA) concentration was significantly (P = 0.0003) increased over total preprandial serum bile acids (PRSBA) concentration at all sample collection periods. The PRSBA and PPSBA concentrations were significantly (P < 0.05) increased at all sample collection periods after administration of UDCA, compared with baseline values. Ursodeoxycholic and tauroursodeoxycholic acids were not detected in serum prior to initiating administration of UDCA. Both bile acids were detected in the serum of all cats 1 and 2 months after UDCA administration and were detected in the serum of 2 cats 3 months after initiating UCDA administration. Hepatic ultrasonographic findings were normal before and after completion of UDCA administration. A mild, focal lymphocytic infiltrate was observed in 3 cats 3 months after initiating UDCA administration. Results of the study indicate that UDCA is absorbed into the systemic circulation of cats after oral administration, undergoes hepatic conjugation, and appears to be safe.     

Hepatic morphology and bile acid composition of bile and urine during chenodeoxycholic acid therapy for radiolucent gallstones

In 9 patients with radiolucent gallstones, percutanous liver biopsy was performed during treatment with chenodeoxycholic acid in a dose of 500 to 750 mg per day for 3-14 months. In 4 patients pretreatment specimens were available for comparison. No sign of hepatic cellular necrosis or bile duct proliferation was noticed in the biopsies. In 2 patients hepatic steatosis was reduced, and in one patient moderate portal tract inflammation decreased during therapy. Mean values of alkaline phosphatases, alanine aminotransferases, prothrombin, and serum lipids remained unchanged and did not exceed normal limits. In 5 patients the urinary bile acid profile was examined during therapy. Chenodeoxycholic acid constituted 27-50%, lithocholic acid 25-63%, and ursodeoxycholic acid 0-13% of total bile acids in urine. The renal excretion of total bile acids was estimated to be less than two mg per day in each patient. From 86 to 100 per cent of the bile acids in urine was sulfated.     

Omeprazole induces altered bile acid metabolism

OBJECT: Direct coaptation of intercostal nerves (ICNs) to the musculocutaneous (MC) nerve was performed to restore elbow flexion in 25 patients with brachial plexus root avulsions. METHODS: Seventy-five ICNs were transected as close as possible to the sternum to obtain sufficient length and then tunneled to the axilla and coapted to the MC nerve. Direct coaptation was achieved in 95% of ICNs, and functional elbow flexion was regained in 64% of the patients. The results were compared with several reported transfer techniques in which either an ICN or other donor nerves were used. CONCLUSIONS: Direct coaptation was equally effective and more straightforward than transfers involving interposition of grafts. The use of alternative donors such as the accessory nerve carries inherent disadvantages compared with the use of ICNs, and the results are not substantially better. Direct ICN-MC nerve transfer is a valuable reconstructive procedure.     

Biliary lipid composition in idiopathic bile acid malabsorption

Human colon cancer frequently develops liver metastasis. Matrilysin (MMP-7), the smallest member of the matrix metalloproteinase (MMP) family, is commonly produced by human colon carcinoma cells and has been suggested to be involved in the progression and metastasis of this type of cancer. In the present study, we tested the effect of a matrilysin-specific antisense phosphorothioate oligonucleotide on liver metastasis of the human colon carcinoma cell line WiDr in nude mice. In culture, the antisense oligonucleotide moderately inhibited the secretion of matrilysin by WiDr cells. Injection of WiDr cells into the spleen of nude mice produced many metastatic tumor nodules in the liver. When the antisense oligonucleotide was injected daily into the mice for 11 days, the formation of the metastatic tumor nodules was strongly inhibited in a dose-dependent manner. An inhibition of liver metastasis of over 70% was obtained at a dose of 120 micrograms of the oligonucleotide per mouse. The antisense oligonucleotide did not inhibit tumor growth in spleen and in liver. A scrambled control oligonucleotide had no effect on liver metastasis of WiDr cells. Our results demonstrate an important role of matrilysin in liver metastasis of human colon cancer and the therapeutic potential of matrilysin antisense oligonucleotides for the prevention of metastasis.     

Comparison of side chain oxidation of potential C27-bile acid intermediates between mitochondria and peroxisomes of the rat liver: presence of beta-oxidation activity for bile acid biosynthesis in mitochondria

The oxidation of the side chains of two potential bile acid intermediates, 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid (THCA) and 3 alpha,7 alpha-dihydroxy-5 beta-cholestanoic acid (DHCA), were investigated in rat liver mitochondria and peroxisomes. Both THCA and DHCA were efficiently oxidized to yield cholic acid and chenodeoxycholic acid, along with 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholest-24-enoic acid and 3 alpha,7 alpha-dihydroxy-5 beta-cholest-24-enoic acid, respectively, in both the mitochondria and peroxisomes. However, the spectrum of the metabolites in the mitochondria differed greatly from those in the peroxisomes. The major products from THCA and DHCA in the mitochondria were 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-chol-22-enoic acid and 3 alpha,7 alpha-trihydroxy-5 beta-chol-22-enoic acid, respectively, which were tentatively identified from the mass spectral data. However, the formation of these C24-unsaturated bile acids was not observed in the peroxisomes. These results strongly suggest that the cleavage of the side chain of the C27-intermediates for bile acid biosynthesis also occurs independently in the mitochondria, not due to the contamination of peroxisomes.     

Radioimmunoassay of serum bile acid levels in biopsy-proved cirrhosis

Serum bile acid levels were determined by a radioimmunoassay for conjugates of cholic acid in 18 patients with biopsy-proved cirrhosis and compared to results of conventional liver function tests. Serum bile acid levels were abnormal in all 18 patients whereas results of the other tests were abnormal in only 50% to 72% of patients. In this group of patients with a well established diagnosis of cirrhosis, serum bile acid levels were a more sensitive indicator of liver dysfunction than standard liver function tests.     

Synthesis of bile acid 24-acyl glucuronides

The role of a surgeon is a complex one. A variety of skills and abilities in a different array of performance tasks is required before he can be competent in his job. As such, there is no simple rule of thumb that can be used to assess a surgeon's performance. As performance assessment and appraisal become increasingly important both for manpower decisions and personal development, it is important that we recognise the different roles a surgeon plays. Only then are we able to subdivide a surgeon's job demands into small manageable portions for analysis. This paper examines the multi-faceted aspects of a surgeon's job, and how each facet should be individually assessed and appraised.     

The amino acid composition of rat bile

The pattern of amino acids in the bile of rats differs from the pattern in the serum of these animals, since bile contains significantly greater amounts of acidic and sulphur-containing amino acids and glycine than serum, while the serum contained more basic amino acids than bile, indicating that secretion of amino acids into bile may involve specific transport processes.     

Neither intestinal sequestration of bile acids nor common bile duct ligation modulate the expression and function of the rat ileal bile acid transporter

The regulatory responses of bile acid (BA) transport in the terminal ileum to perturbations in BA homeostasis are complex, and conflicting results have been reported by different investigators. These studies were designed to examine the response of this system to a reduction in ileal bile salt concentrations at both a functional and molecular level. Common bile duct ligation (BDL) or feeding of a novel bile acid-binding compound, GT31-104HB, for 7 days were used to reduce ileal apical membrane bile salt flux. Apical bile acid transport function was assessed by examining sodium-dependent uptake of [3H]-taurocholate (TC) into brush border membrane vesicles (BBMV). Expression of the apical sodium-dependent bile acid transporter (ASBT) and the ileal lipid-binding protein (ILBP) were assessed by Western blotting with quantitation using [125I]-labeled secondary antibody and a phosphorimager. Neither common BDL nor intestinal sequestration of BA led to a change in ileal bile acid transport function or the expression of the ASBT or the ILBP. These results indicate that a reduction in presentation of bile salts to the apical surface of the terminal ileum does not modulate the expression of the genes involved in their transport.     

Alteration of bile acid metabolism by cimetidine in healthy humans

BACKGROUND: To clarify an effect of cimetidine on bile acid metabolism, we evaluated whether an increased deconjugation of bile acids would occur in healthy humans who have received cimetidine. We examined: 1) whether healthy volunteers taking cimetidine would have positive bile acid breath tests because of bacterial overgrowth in the jejunum; 2) whether the isolated bacteria would exhibit deconjugation ability; and 3) whether a change in gastric pH was related to the bacterial overgrowth. METHODS: We evaluated 73 healthy Japanese volunteers; 53 of them received cimetidine and 20 did not. Deconjugation of bile acids was detected as 14CO2 specific activity of expired air measured by a bile acid breath test giving 5 muCi of oral glycine-1-(14)C labeled glycocholate. Aspiration of jejunal fluids was performed by a double lumen tube with a rubber cover on the tip, and deconjugation ability of bacteria was evaluated using thin layer chromotography. RESULTS: Samples of expired breath from the 53 healthy volunteers showed a significant increase in 14CO2 specific activity after the administration of cimetidine rather than before the administration of cimetidine. Bacterial over-growth was found in the jejunal fluid after the administration of cimetidine. The administration of tetracycline to 27 subjects significantly reduced the 14CO2 specific activity. The following species were identified in the jejunal fluid samples obtained from the subjects: enterococcus, Lactobacillus bifidus, Bacteroides vulgatus, B uniformis, Eubacterium lentum, E parvum, and Escherichia coli. Except for E coli, all of the bacterial species identified deconjugated bile acids. We observed a significant relationship between 14CO2's specific activity and gastric pH before and after administration of cimetidine, respectively. CONCLUSIONS: Healthy volunteers who received cimetidine showed an increased deconjugation of bile acid caused by overgrowth of bacteria in the jejunum, which can deconjugate bile acids. The bacterial overgrowth is probably associated with a shift to neutral pH in the gastric juice caused by cimetidine.     

Electrogenicity of Na(+)-coupled bile acid transporters

The Na(+)-bile acid cotransporters NTCP and ASBT are largely responsible for the Na(+)-dependent bile acid uptake in hepatocytes and intestinal epithelial cells, respectively. This review discusses the experimental methods available for demonstrating electrogenicity and examines the accumulating evidence that coupled transport by each of these bile acid transporters is electrogenic. The evidence includes measurements of transport-associated currents by patch clamp electrophysiological techniques, as well as direct measurement of fluorescent bile acid transport rates in whole cell patch clamped, voltage clamped cells. The results support a Na+:bile acid coupling stoichiometry of 2:1.     

Characterization of glucuronic acid conjugates of a novel angiotensin receptor antagonist

Nanogram quantities of glucuronic acid conjugates of GR117289 in rat and dog bile have been analysed by semi-microbore high-performance liquid chromatography (HPLC)/ionspray mass spectrometry with on-line UV diode array detection. The determination of drug metabolites in bile has often proved problematical due to the large number of endogenous components in this biological matrix, in particular the bile acids. Semi-microbore HPLC is useful for concentrating small quantities of material and, in combination with an on-line diode array detector, for distinguishing between drug related and endogenous components. A novel angiotensin II receptor antagonist, GR117289, had proved difficult to analyse by thermospray mass spectrometry because of its thermal lability. The use of the less thermally dependent technique of ionspray mass spectrometry allowed the characterization of nanogram quantities of glucuronic acid metabolites of GR117289 in bile.