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  • 1
    Electronic Resource
    Electronic Resource
    Valpromide is a poor inhibitor of the cytosolic epoxide hydrolase (1989)
    Springer
    Archives of toxicology 63 (1989), S. 157-159 
    Details
    ISSN: 1432-0738
    Keywords: Cytosolic epoxide hydrolase ; Valpromide ; Liver ; Adult subjects and fetuses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of the antiepileptics valpromide and sodium valproate on the cytosolic epoxide hydrolase was studied in human fetal liver, kidneys and adrenals and from human adult liver and kidneys. Trans-stilbene oxide was used as substrate. Valpromide (10 mM) lowered the activity of the epoxide hydrolase to one half of the control in all organs studied. Sodium valproate (10 mM) was less powerful as an inhibitor than valpromide; however, it exerted a significant inhibition in all tissues studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00316440
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  • 2
    Electronic Resource
    Electronic Resource
    Sulphation of the heterocyclic amine 1,2,3,4-tetrahydroisoquinoline in the human liver and intestinal mucosa: interindividual variability (1997)
    Springer
    Archives of toxicology 71 (1997), S. 477-481 
    Details
    ISSN: 1432-0738
    Keywords: Key words Sulphotransferase ; Liver ; Intestine ; Man ; Variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The sulphation rate of 1,2,3,4-tetrahydroisoquinoline (TIQ) was measured in the human liver and in the intestinal mucosa isolated from the transverse colon, ileum and duodenum. The rate (mean ± SD) of hepatic TIQ sulphation was 500 ± 174 pmol/min per mg in women (n=61) and 591 ± 201 in men (n=39; P=0.0087), varying over one order of magnitude in men and women. The sulphation rate of testosterone showed the same sex-dependent pattern and was correlated (r=0.6055; P〈0.001) with that of TIQ. The frequency distribution of TIQ sulphation rate in human liver was bimodal: 70% of the population fell into the low-activity subgroup and the remaining 30% feel into the high-activity subgroup. In the colon (n=56), the rate of TIQ sulphation was 30.4 ± 15.6 pmol/min per mg and the values were similar in men and women (29.8 and 30.9 pmol/min per mg, respectively) but, varied over one order of magnitude and correlated (r=0.7231; P〈0.001) with that of 4-nitrophenol. The rate of TIQ sulphation changed along the human bowel and mean (±SD) estimates for duodenum, ileum and transverse colon were 444 ± 25, 182 ± 87  and 30.4 ± 15.6 pmol/min per mg, respectively. The present results are consistent with the view that the heterocyclic amine TIQ is sulphated in the human liver and intestinal mucosa. TIQ-sulphotransferase activity varies among subjects and is mostly associated with the liver and duodenum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050415
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  • 3
    Electronic Resource
    Electronic Resource
    Hydroxylation of dibutylnitrosamine in the human liver and intestinal microsomal fractions (1986)
    Springer
    Archives of toxicology 58 (1986), S. 196-198 
    Details
    ISSN: 1432-0738
    Keywords: Dibutylnitrosamine ; Metabolism ; Human ; Rat ; Liver ; intestine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The metabolism of the bladder carcinogen N-nitroso-di-n-butylamine (NDBA) was studied in microsomal preparations of tissues of patients of both sexes, aged 59–69 years undergoing abdominal surgery. Samples of liver, ileum, and colon were of normal histological appearance. For comparison, samples of rat liver and small intestinal mucosa microsomes were included in the study. Using 1-14C-labeled NDBA, the biotransformation to hydroxylation products retaining the nitroso group, NDBA-2-OH, NDBA-3-OH, and NDBA-4-OH, respectively, was investigated by reversed phase HPLC. In order to separate these metabolites, pooled samples were analysed by normal phase HPLC. The rate of hydroxylation of NDBA was found to be 5.5 times higher in rat liver microsomes compared to those from human liver (2.86±0.29 vs 0.52±0.03 nM x min−1 x mg−1). NDBA-3-OH proved to be the major metabolite formed (〉80% of total metabolites). The metabolism of NDBA was low but detectable in seven out of nine specimens of human gut, 0.1–0.5 nM x mg−1 in 1 h of incubation, and of the same order of magnitude in rat intestinal tissue (0.4–0.6 nM x mg−1).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00340981
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  • 4
    Electronic Resource
    Electronic Resource
    Cytosolic epoxide hydrolase in humans: development and tissue distribution (1988)
    Springer
    Archives of toxicology 62 (1988), S. 254-257 
    Details
    ISSN: 1432-0738
    Keywords: Cytosolic epoxide hydrolase ; Humans ; Fetuses ; Adult subjects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cytosolic epoxide hydrolase activity was measured towards trans-stilbene oxide in 41 human adult livers, in 40 fetal livers, in 17 placentas and in fetal and adult lungs, kidneys and gut. The cytosolic epoxide hydrolase activity was measurable in all specimens investigated. The rate of formation of trans-stilbene glycol (pmol/min per mg protein, mean±SD) was 55.2±89.6 (fetal liver). 303.2±73.2 (adult liver) and 18.8±13.1 (placenta) In the fetal extrahepatic tissues, the cytosolic epoxide hydrolase activity was 70.0±9.4 (adrenals), 47.6±7.2 (gut), 69.4±22.5 (kidneys) and 43.2±19.2 (lungs) pmol/min per mg protein, whereas in the adult tissues it was 131.2±63.1 (kidneys), 27.8±20.3 (intestine), 8.5±2.8 (lungs) and 7.2±4.2 (urinary bladder) pmol/min per mg protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00332483
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  • 5
    Electronic Resource
    Electronic Resource
    Distribution of 2-naphthol sulphotransferase and its endogenous substrate adenosine 3′-phosphate 5′-phosphosulphate in human tissues (1989)
    Springer
    European journal of clinical pharmacology 37 (1989), S. 317-320 
    Details
    ISSN: 1432-1041
    Keywords: 2-naphthol sulphotransferase ; adenosine 3′-phosphate 5′-phosphosulfate ; liver ; kidney ; lung ; intestine ; tissue distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The activity of sulphotransferase towards 2-naphthol and the concentration of its endogenous substrate, adenosine 3′-phosphate 5′-phosphosulphate (PAPS), have been measured in five specimens of human liver, lung, and kidney, and the mucosa from the ileum and the ascending, descending and sigmoid colon. The activity of 2-naphthol sulphotransferase (mean nmol·min−1·mg−1 protein) was 1.82 (liver); 0.034 (kidney); 0.19 (lung); 0.64 (ileum); 0.47 (ascending colon); 0.50 (descending colon); 0.40 (sigmoid colon). The concentration of PAPS (mean nmol·g−1 wet tissue) was 22.6 (liver); 4.8 (kidney); 4.3 (lung); 12.8 (ileum); 8.1 (ascending colon); 7.5 (descending colon); 6.2 (sigmoid colon). The concentration of PAPS and the activity of 2-naphthol sulphotransferase were higher in the liver than in the extrahepatic tissues. There was significant difference between ileum and ascending colon, both the activity of sulphotransferase and the concentration of PAPS being higher in the former. 2-Naphthol sulphotransferase activity and the concentration of PAPS have consistent distribution patterns. Differences between the tissues studied were more marked for sulphotransferase than for its endogenous substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00679793
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  • 6
    Electronic Resource
    Electronic Resource
    Minoxidil sulphation in human liver and platelets (1993)
    Springer
    European journal of clinical pharmacology 45 (1993), S. 337-341 
    Details
    ISSN: 1432-1041
    Keywords: Minoxidil ; sulphotransferase ; liver ; extrahepatic tissues ; platelets ; interindividual variability ; adults ; neonates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Minoxidil requires to be sulphated to exert its hypotensive effect. We report on interindividual variability in the rate of minoxidil sulphation in 118 specimens of human liver and in platelets obtained from 100 healthy subjects and 100 newborns. The frequency distribution histogram of the hepatic activity of minoxidil sulphotransferase was positively skewed; the mean was 631 pmol · min−1 · mg−1. After logarithmic transformation of the enzyme activity, the frequency distribution histogram became symmetrical and did not significantly deviate from normality. The rate of minoxidil sulphation was not different in platelets from adults (0.74 pmol · min−1 · mg−1) and newborns (1.16 pmol · min−1 · mg−1). The frequency distribution histograms were positively skewed and the results of normal equivalent deviation analysis was compatible with the presence of at least two subgroups of sulphotransferase in liver and platelets. Thus, two phenotypes of sulphotransferase exist in human liver and platelets, and the “extensive sulphator” phenotype contributes to skewing the frequency distribution. In platelets, the percentage of subjects that fall in the two subgroups is different at birth and in adulthood. This can explain the different shape of the frequency distribution in newborn and adult platelets and suggests that platelet minoxidil sulphotransferase undergoes modification after birth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00265951
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  • 7
    Electronic Resource
    Electronic Resource
    Stereoselective inhibition by chloroquine of histamine N-methyltransferase in the human liver and brain (1994)
    Springer
    European journal of clinical pharmacology 47 (1994), S. 345-349 
    Details
    ISSN: 1432-1041
    Keywords: Chloroquine ; Stereoselectivity ; Histamine ; methyltransferase ; liver ; brain ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract This study was designed to determine whether both enantiomers of chloroquine inhibit histamine N-methyltransferase. The mean estimates of IC50 for the d- and l-enantiomers of chloroquine were 4.9 and 17.8 μM (liver), respectively and 6.9 and 21.6 μM (brain), respectively. Ki estimates were significantly lower with d- than with l-chloroquine; hence, d-chloroquine interacts with the enzyme more effectively than l-chloroquine. If the adverse effects of chloroquine are due to the inhibition of histamine N-methyltransferase, therapy with the l-enantiomer might have lower toxicity. The residual activity of histamine N-methyltransferase should reflect both the degree of inhibition by chloroquine and the level of enzyme expression. The rate of histamine methylation was measured in 100 human liver samples and its range and fold of variation were 29% and threefold, respectively. Susceptibility to chloroquine should be greater in subjects with limited expression of histamine N-methyltransferase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00191166
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  • 8
    Electronic Resource
    Electronic Resource
    Sulphation and glucuronidation of ritodrine in human foetal and adult tissues (1993)
    Springer
    European journal of clinical pharmacology 44 (1993), S. 259-264 
    Details
    ISSN: 1432-1041
    Keywords: Ritodrine ; sulphation ; glucuronidation ; man ; adult tissues ; fetal tissues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Ritodrine is a β2-adrenoceptor agonist used for the management of preterm labour. It is inactivated by conjugation with sulphate and glucuronic acid. There is more ritodrine sulphate than ritodrine glucuronide in urine from the newborn whereas equal amounts of ritodrine glucoronide and sulphate are excreted in maternal urine [Clin. Pharmacol. Ther 44, 634–641, 1988]. We show that, in the mid-gestational human fetal liver, ritodrine sulphotransferase is well expressed, whereas the glucuronidation of ritodrine is little developed compared to the adult liver. The average sulphotransferase activity was 308 pmol·min−1 per mg protein in fetal (N=48) and 145 pmol·min−1 per mg protein in adult (N=32) liver. The rates of ritodrine sulphation in fetal gut, lung and kidney were higher than in the corresponding adult tissues. The development and tissue distribution patterns of ritodrine sulphotransferase are consistent with those of dopamine sulphotransferase. Ritodrine and dopamine are sulphated by thermolabile enzymes. The activity of glucuronyl transferase was measurable in only 5 of the 48 foetal livers assayed, and in those in which could be assayed, the average activity was 44.6 pmol·min−1 per mg protein, one-tenth of that in adult livers (524 pmol·min−1 per mg protein).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00271368
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  • 9
    Electronic Resource
    Electronic Resource
    Human liver budesonide sulphotransferase is inhibited by testosterone and correlates with by testosterone sulphotransferase (1994)
    Springer
    European journal of clinical pharmacology 46 (1994), S. 49-54 
    Details
    ISSN: 1432-1041
    Keywords: Budesonide ; liver ; man ; sulphotransferase ; testosterone ; drug metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Budesonide, a corticosteroid used in the treatment of asthma and allergic reactions, is almost entirely cleared by metabolism in man. We describe the sulphation of budesonide in human liver and lung and provide evidences that the sulphation of budesonide is catalysed by testosterone sulphotransferase. A rapid and reproducible radiometric assay for budesonide sulphotransferase is described. Liver specimens were obtained from 35 men and 65 women and lung specimens from 2 women and 17 men. The average hepatic budesonide sulphation rate was significantly higher in men (41.1 pmol·min−1·ml−1) than women (28.2 pmol·min−1·mg−1). In the lung, the mean budesonide sulphation rate was 5.0 pmol·min−1·mg−1. Testosterone strongly inhibited the hepatic sulphation of budesonide, whereas p-nitrophenol and dopamine were poor inhibitors; the IC50 was 7.0 uM (testosterone), 320 uM (p-nitrophenol) and 510 uM (dopamine). The hepatic rates of testosterone, p-nitrophenol and dopamine sulphation were measured in the same samples assayed for budesonide sulphotransferase. There was a correlation between the hepatic rates of budesonide and testosterone sulphation (P〈0.001; r=0.810). The activity of testosterone sulphotransferase was significantly greater in men than women (22.0 vs. 17.2 pmol·min−1·mg−1), wheres those of dopamine and p-nitrophenol sulphotransferase were not sex dependent. The hepatic activity of budesonide sulphotransferase parallels that of testosterone suggesting that sulphation is an important reaction in the metabolism of budesonide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195915
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  • 10
    Electronic Resource
    Electronic Resource
    Distribution of UDP-glucuronosyltransferase and its endogenous substrate uridine 5′-diphosphoglucuronic acid in human tissues (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 345-350 
    Details
    ISSN: 1432-1041
    Keywords: UDP-glucuronosyltransferase ; Drug glucuronidation ; 5′-uridine diphosphoglucuronic acid ; human tissues ; enzyme kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The activity of UDP-glucuronosyltransferase (UDPGT) and the concentration of its endogenous substrate, 5′-diphosphoglucuronic acid (UDPGA), have been measured in human liver, kidney, lung and intestinal mucosa. The activity of UDPGT was tissue- and substrate-dependent. The liver/kidney and liver/intestine ratios for UDPGT varied over one order of magnitude with three substrates. The highest activity of UDGPT in extrahepatic tissues was in the kidney, with 1-naphthol as substrate; it was about half of the hepatic activity. The concentration (μmol · kg−1) of UDPGA was 279 (liver), 17.4 (kidney), 19.3 (intestinal mucosa) and 17.2 (lung), it was at least 15-fold higher in liver than the other tissues, and the concentration in kidney, lung and intestinal mucosa was similar. The kinetics of UDPGT in a liver homogenate at varying concentrations of UDPGA and fixed concentration of 1-naphthol, ethinyloestradiol, and morphine was also measured. The apparent kM for UDPGT depended upon the chemical nature of the UDPGA-acceptor substrate; average values of kM were 63, 300, and 700 μmol · 1−1 for 1-naphthol, ethinyloestradiol and morphine respectively. These values are, respectively, lower, similar to and higher than the hepatic concentration of UDPGA. Under certain circumstances UDPGA may be the limiting factor in the in vivo glucuronidation of drugs by extrahepatic tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00314965
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