Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.31 (beta-glucuronidase)
 7,680 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The expression of a number of enzymes involved in drug metabolism, membrane function etc. was compared in hyperplastic and neoplastic lesions of the rat bladder and in human bladder tumours. Transitional cell carcinomas (TCC) in both rat and Man were characterized by decreased alkaline phosphatase (ALP) and increased gamma-glutamyl transpeptidase (GGT), beta-glucuronidase (beta-G1), succinate dehydrogenase (SD) and glucose-6-phosphate dehydrogenase (G6PD) activities. In addition, binding for antibodies specific for different cytochrome P-450 species (UT50, PB3a, MC1, MC2) and microsomal epoxide hydrolase (mEHb) was elevated in both murine and human tumours. Comparison of the enzyme phenotype in hyperplastic lesions induced by freeze ulceration or uracil administration with that in preneoplastic papillary or nodular hyperplasia (PNH) and TCC suggested, however, that most of the alteration in enzyme content or activity was non-specific and related to requirements for epithelial cell proliferation. On the other hand, the decreased ALP, and increased GGT and beta-G1 activity appeared more directly related to neoplastic transformation. The results suggested that qualitative differences exist between reactive hyperplasia and preneoplastic or neoplastic lesions in the urinary bladder. The finding of increased cytochrome P-450, in clear contrast to the reduction characteristic of preneoplastic hepatic lesions, may be important with regard to the observed difference in neoplastic transformation between the bladder and liver in response to drug metabolising enzyme inducers.
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PMID:Comparison of enzyme phenotypes in human bladder tumours and experimentally induced hyperplastic and neoplastic lesions of the rat urinary bladder. A combined histochemical and immunohistochemical approach. 256 27

This paper assesses the capacity of animal models to predict human response to carcinogenic agents with consideration for the heterogeneity of humans. It is widely accepted that human susceptibility to toxic substances, including carcinogens, is highly variable. Conventional rodent models are usually highly inbred and valued for their ability to display characteristic homogeneity. Current practice assumes that the homogeneity of response to toxic agents, including carcinogens, in the rodent model will be representative of humans. The issue then becomes, To which of the broad spectrum of human responses are specific animal models likely to be related? This paper examines the extent of human heterogeneity over a broad range of biochemical characteristics (e.g., aryl hydrocarbon hydroxylase activity, epoxide hydrase activity, beta-glucuronidase activity, debrisoquine hydroxylation, DNA-adduct formation) with emphasis on those biochemical characteristics that affect responses to carcinogens. Examples are presented to compare the heterogeneity of selected animal models for these biochemical characteristics as they relate to the spectrum of human responses noted above. The paper presents a theoretical perspective for determining to which part of the human population response spectrum common animal models are most likely to be extrapolated.
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PMID:Comparative biology of test species. 328 8

Carbamazepine 10,11-oxide (1a,10b-dihydro-6H-dibenzo[b,f]oxireno[d]azepine-6-carboxamide), a key intermediate in carbamazepine metabolism, was found to be unusually resistant to enzymatic hydrolysis when incubated with microsomal and cytosolic fractions from rabbit, rat, and guinea pig livers. However, its hydrolysis product, trans-10,11-dihydro-10,11-dihydroxy-5H-dibenzo[b,f]azepine-5-carboxamide , was excreted, as previously reported, both in the free and in conjugated forms, as the main metabolite in the urine of humans under carbamazepine treatment. The free diol and that obtained after treatment with beta-glucuronidase/arylsulfatase were both found by Mosher's method to be formed in an enantiomeric excess of 80%, the prevalent enantiomer having the (-)-10S,11S absolute configuration, as determined by applying the CD exciton coupling method to its bis[p-(dimethylamino)benzoyl] ester. This finding confirms the pronounced enantioselectivity of the microsomal epoxide hydrolase toward meso and racemic substrates, but is in contrast with the prevalent formation of (R,R)-diols in most other known cases of enzymatic hydrolysis of epoxides. Preparatively useful syntheses of the racemic trans-10,11-dihydro-10,11-diol and of 9-(hydroxymethyl)-10-carbamoylacridan, another carbamazepine metabolite, are reported for the first time.
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PMID:The metabolism of carbamazepine in humans: steric course of the enzymatic hydrolysis of the 10,11-epoxide. 357 65

The capacity of animal models to predict the responses of humans to carcinogenic agents in light of the occurrence of human heterogeneity is assessed in this paper. It is widely accepted that human susceptibility to toxic substances, including carcinogens, is highly variable. At the same time, it is believed that the conventional rodent models, which are usually highly inbred and reared in standard ways, display a very homogeneous response to toxic agents, including carcinogens. The question then becomes, To which narrow band of the broad spectrum of human responses can specific animal models likely be extrapolated? First, the occurrence of human heterogeneity is examined with respect to a broad range of biological characteristics (e.g., aryl hydrocarbon hydroxylase activity, epoxide hydrase activity, glutathione S-transferase activity, beta-glucuronidase activity, debrisoquine hydroxylation, and DNA adduct formation), with particular emphasis on those which affect responses to carcinogens. Second, the occurrence of heterogeneity for selected animal models for these characteristics is assessed and the outcomes are related to the spectrum of human responses noted above.
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PMID:Animal extrapolation and the challenge of human heterogeneity. 382 97