Urine bile acid conjugates found

Some structures of bile acid conjugates found in urine or plasma of a child with neonatal hepatitis of unknown etiology. 

Male Wistar rats given single oral doses of 10, 50, or 250 mg/kg of1,4-dichlorobenzene (vehicle not given) excreted the majority of derived from 1,4-dichlorobenzene in the urine as either the sulfate conjugate (60%) or the glucuronide (30%). Bile contained 5 and 30% of the total radioactivity after the low and high doses, respectively. Only minor amounts of mercapturic acid were found (Hissink et al. 1997). 

TNT is readily absorbed through skin, especially when skin is moist. It is excreted in urine more than in feces some is found in bile. The major biotransformation reaction is nitroreduction and, to a lesser extent, oxidation. The main metabolite formed by nitroreduction seems to be 4-amino-2,6-dinitrotoluene (4-ADNT). Other metabolites include 2-amino-4,6-dinitrotoluene (2-ADNT), 2,4-diamino-6-nitrotoluene, and 2,6-diamino-4-nitrotoluene. The metabolites are excreted in the urine as glucuronide conjugates and in the free form. Ring oxidation products of TNT such as trinitrobenzylalcohol, trinitrobenzoic acid, and simultaneous oxidation and reduction metabolites such as 2,6-dinitro-4-amino-benzylalcohol and 2,6-dinitro-4-amino-m-cresol are of less importance. Untransformed TNT is also excreted in the urine. ADNT and TNT concentrations were found in workers in explosives factories. 4-ADNT excretion was reported to be complete within 3M days after exposure. However, another study reported detectable urine concentration of ADNT in explosives workers even after 17 days away from the workplace. 

Virtually all markers of peroxisomal function are lipid-boimd or protein-bound they are present in the plasma, but they are not excreted into the urine. Exceptions are the water-soluble glycine-, taurine-, or glucuronic acid conjugates of bile acids which may be found in the urine. The general clinical chemistry lab will not give consistent clues to the existence of peroxisomal disease as there is no readily accessible end product of peroxisomal substrates. 

GC-MS analysis is used to confirm the identities of ions in the LSI-MS urine spectrum and show that the excretion of abnormal cholanoids is >20 times normal. In the case of 5 ff-reductase deficiency GC-MS analysis should show that S-oxo-A" bile acids account for >70% of the total urinary bile acid excretion. In the case of sterol 27-hydroxylase deficiency (CTX), GC-MS analysis should indicate that the major cholestane pentols in the urine are 3,7,12,22,25 and 3,7,12,23,25-pentols. (One patient has been described who had familial cholestatic liver disease associated with greatly increased urinary excretion of 5jff-cholestane-3a,7a,12a,24 S,25-pentol [see previous table]). Liquid secondary ion-tandem mass spectrometry (LSI-MS/ MS) is an alternative method to GC-MS and can rapidly confirm the identity of a number of diagnostic ions that are found in the LSI-MS spectrum of urine. These include sulphated and taurine-conjugated abnormal metabolites such as those observed in 3 ff-HSDH deficiency (32.1), 5)9-reductase deficiency (32.2), oxysterol 7a-hydroxylase deficiency (32.4) and peroxisomal disorders [13]. 

Although mercapturic acids are normally the major thioether products of lipophilic xenobiotics found in urine of mammals, small amounts of the corresponding S-cysteine conjugates are also frequently excreted. All four thioether products formed during mercapturic acid biosynthesis are routinely excreted in bile. 

After initial metabolism, most of the detoxified portion of PAH compounds are excreted into the bile as metabolites, then subsequently eliminated in the faeces. A smaller proportion is excreted in urine. The two major metabolites of benzo( )pyrene found in urine are 3-hydroxy- and 9-hydroxybenzo(o)pyrene, part of them being conjugated to sulphate or glucuronic acid (Bouchard and Viau, 1997 Ramesh et al., 2001). The process of excretion of PAH compounds into the intestine via the bile, reabsorption, and return to the liver by the portal circulation (enterohepatic recirculation) has been demonstrated to occur for 7,12-dimethylbenzo( )anthracene, benzo(o)pyrene, anthracene and pyrene (Ramesh et al., 2004). Enterohepatic circulation extends the residence time of PAHs in the body and may lead to long half-lives of reactive PAH metabolites. Though enterohepatic recycling of PAHs has... 

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