1. The rate of conjugation of benzoic acid with glycine was measured in the homogenates of 110 specimens of human liver and in 67 specimens of human renal cortex. 2. The assay for the formation of benzoyl glycine consisted of measuring the formation of benzoyl glycine from (14C) benzoic acid and glycine in the presence of coenzyme A and ATP. 3. In human liver, the mean (+/- SD) and coefficient of variation for the formation rate of benzoyl glycine were 254 +/- 90.5 nmol min-1 per g liver and 36%, respectively. There was a weak, but significant, negative correlation (r = -0.339, p < 0.001) between the rate of formation of benzoyl glycine and the liver donor's age. 4. In the human kidney, the rate of benzoyl glycine formation was normally distributed. The mean (+/- SD) and coefficient of variation were 321 +/- 99.3 nmol min-1 per g kidney and 31%, respectively. 5. These in vitro results are consistent with the view that the in vivo rate of conjugation of carboxylic acid with glycine varies among subjects and is normally distributed.
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.
1 Glucuronidation and sulphation of ethinyloestradiol (EE2) was studied in human liver.Microsomal
1 The activities of microsomal glucuronyltransferase and thiomethyltransferase, and those of cytosolic sulphotransferase, acetyltransferase, glutathione transferase and thiomethyltransferase were measured in abnormal (cirrhosis and chronic hepatitis) and normal livers. 2 Glucuronyltransferase and sulphotransferase were investigated with 2-naphthol and ethinyloestradiol as substrates. p-Aminobenzoic acid, benzo(a)pyrene-4,5-epoxide and 2-mercaptoethanol were the substrates of acetyltransferase, glutathione transferase and thiomethyltransferase, respectively.3 Enzyme activities are expressed as nmol min-1 incubation mg-1 protein and the averages (± s.d.) are given. With 2-naphthol as substrate, the glucuronyltransferase activity was 6.55 ± 4.10 (abnormal liver, n = 33) and 7.81 ± 4.02 (normal liver, n = 26) (NS); whereas sulphotransferase activity was 0.28 ± 0.18 (abnormal liver, n = 35) and 0.68 ± 0.43 (normal liver, n = 26) (P < 0.01). Glucuronyltransferase activity towards ethinyloestradiol was 102.5 ± 56.9 (abnormal liver, n = 30) and 107 ± 59.9 (normal liver, n = 26) (NS), whereas sulphotransferase activity was 57.2 ± 36.0 (abnormal liver, n = 35) and 122 ± 67.6 (normal liver, n = 28) (P < 0.01). Acetyltransferase activity was 0.84 ± 0.83 (abnormal liver, n = 35) and 3.84 ± 1.65 (normal liver, n = 26) (P < 0.01). Glutathione transferase activity was 0.83 ± 0.68 (abnormal liver, n = 35) and 2.90 ± 1.59 (normal liver, n = 25) (P < 0.01) and thiomethyltransferase activity was 1.00 ± 0.69 (abnormal liver, n = 34) and 3.99 ± 1.49 (normal liver, n = 25) (P < 0.01). 4 Liver disease lowers the activities towards the substrates studied of sulphotransferase, acetyltransferase, glutathionetransferase and thiomethyltransferase but not that of glucuronyltransferase. Thus, overall hepatic conjugating capacity is decreased in liver injury. However, enzyme activity is substrate dependent and it is not possible to extrapolate the results for other compounds.
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