Genetically engineered V79 chinese hamster cell expression of purified cytochrome <i>P</i>‐450iib1 monooxygenase activity

Platt, Karl L.; Molitor, Elvira; Döhmer, Johannes; Dogra, Satish C.; Oesch, Franz

doi:10.1002/jbt.2570040102

Cited by 61 publications

(20 citation statements)

References 35 publications

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“…2). Both dioxane treatments induced several fold (about 18-20) 2B1/2-dependent 16b-testosterone hydroxylase, but only the acute dioxane administration was able to induce, although weakly, CYP3A-linked 6b-testosterone hydroxylase (Platt et al 1989), in keeping with the ErD data shown in Table 1. In addition, to our surprise, it was also observed that both 1,4-dioxane treatments induced 17OT-, 16a-and particularly 2a-testosterone hydroxylases linked to CYP2C11 (Platt et al 1989), the major P450 isoform constitutively present in the liver (Fujita et al 1989).…”

Section: Effects Of Dioxane Administration On Hepatic P450 Activitiessupporting

confidence: 82%

“…With both treatment regimens, strong and quite similar increases of CYP2B1/ 2-linked PROD and 2E1-linked p-NPH activities were observed in the liver. However, these treatments were not equivalent since dioxane administration by gavage but not that by drinking water also induced CYP3A-dependent activities such as ErD and 6b-testosterone hydroxylase (Arlotto et al 1987;Platt et al 1989). The induction of 2B1/2 in the liver following both acute and chronic dioxane treatment was also confirmed by marked enhancement of 16b-testosterone hydroxylase, a marker activity for this isoform (Platt et al 1989).…”

Section: Discussionmentioning

confidence: 69%

“…However, these treatments were not equivalent since dioxane administration by gavage but not that by drinking water also induced CYP3A-dependent activities such as ErD and 6b-testosterone hydroxylase (Arlotto et al 1987;Platt et al 1989). The induction of 2B1/2 in the liver following both acute and chronic dioxane treatment was also confirmed by marked enhancement of 16b-testosterone hydroxylase, a marker activity for this isoform (Platt et al 1989). The induction of 2E1 was also demonstrated by the enhancement of (x-1)-hydroxylation rate of lauric acid in the liver microsomes from both dioxane treatment groups.…”

Section: Discussionmentioning

confidence: 94%

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Effects of dioxane on cytochrome P450 enzymes in liver, kidney, lung and nasal mucosa of rat

et al. 2004

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The effect of acute and chronic dioxane administration on hepatic, renal, pulmonary and nasal mucosa P450 enzymes and liver toxicity were investigated in male rats. The acute treatment consisted of two doses (2 g/kg) of dioxane given for 2 days by gavage, whereas the chronic treatment consisted of 1.5% of dioxane in drinking water for 10 days. Both the acute and chronic dioxane treatments induced cytochrome P450 2B1/2- and P450 2E1-dependent microsomal monooxygenase activities (pentoxyresorufin O-depentylase and p-nitrophenol hydroxylase) in the liver, whereas in the kidney and nasal mucosa, only the 2E1 marker activities were enhanced. In addition in the liver, an induction of 2alpha-testosterone hydroxylase (associated with the constitutive and hormone-dependent P450 2C11) was also revealed, whereas the hepatic P450 4A-dependent omega-lauric acid hydroxylase was not enhanced by any dioxane treatment. These inductions were mostly confirmed by western blot analysis of liver, kidney and nasal mucosa microsomes. In the lung, no alteration of P450 activities was observed. To assess the mechanism of 2E1 induction, the hepatic, renal and nasal mucosa 2E1 mRNA levels were also examined. Following two kinds of dioxane administration, in the liver the 2E1 induction was not accompanied by a significant alteration of 2E1 mRNA levels, while both in the kidney and nasal mucosa the 2E1 mRNA increased about 2- to 3-fold, indicating an organ-specific regulation of this P450 isoform. Furthermore, dioxane was unable to alter the plasma alanine aminotransferase activity and hepatic glutathione (GSH) content, examined as an index of toxicity, when it was administered into rats with P450 2B1/2 and 2E1 preinduced by phenobarbital or fasting pretreatment. These results support the lack of or a poor formation of reactive and toxic intermediates during the biotrasformation of this solvent, even when its metabolism was enhanced by P450 inducers. The chronic administration of dioxane was also unable to induce the palmitoyl CoA oxidase, a marker of peroxisome proliferation, excluding this as a way to explain its toxicity. Thus, although the mechanism of dioxane carcinogenicity remains unclear, the present results suggest that the induction of 2E1 following a prolonged administration of dioxane might provide oxygen radical species, and thereby contribute to its organ-specific toxicity.

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Section: Effects Of Dioxane Administration On Hepatic P450 Activitiessupporting

confidence: 82%

Section: Discussionmentioning

confidence: 69%

Section: Discussionmentioning

confidence: 94%

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Effects of dioxane on cytochrome P450 enzymes in liver, kidney, lung and nasal mucosa of rat

et al. 2004

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“…Testosterone hydroxylase was assayed as reported previously according to an HPLC method described by Platt et al [26], as previously reported [27]. Testosterone metabolites were resolved in a C18 RP Supelco column (250 × 4.6 mm) using an isocratic elution with methanol plus tetrahydrofuran (THF) 7.5% and H 2 O + THF 7.5% (27:73 v/v) for 8 min followed by a linear gradient reaching 42:58 v/v for 12 min and a final period of isocratic elution for further 10 min.…”

Section: Enzyme Assaysmentioning

confidence: 99%

Cloning, tissue expression, and inducibility of CYP 3A79 from sea bass (Dicentrarchus labrax)

Vaccaro

Salvetti

Carratore

et al. 2007

J Biochem & Molecular Tox

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Multiple members of the CYP3A subfamily have been identified and intensively studied in mammals as they represent prominent CYP enzymes involved in drug metabolism. Also in fish, some CYP3A genes have been identified by cDNA cloning and immunological techniques, but relatively little is known about their function, distribution, and inducibility. In this study, a novel CYP3A, designated as CYP3A79 was isolated from adult male sea bass, an economically valuable species in fisheries. The sea bass CYP3A79 that was cloned contained an open-reading frame of 1512 bp that encoded a 504 amino acid protein and shared a high-sequence identity with medaka, killifish, and trout CYP3As. Interestingly, CYP3A79 also shares five of six substrate recognition sites (SRS) with the SRS of other fish CYP3As, suggesting an evolutionary conservation of the function of these enzymes. In this fish, we also investigated the expression of CYP3A79 and its susceptibility to induction by various compounds including clotrimazole and dehydroepiandrosterone, two strong ligands of zebrafish PXR. The expression of CYP3A79 mRNA was detected by RT-PCR only in the intestine and liver. The immunoblot analysis by antitrout CYP3A27 confirmed the presence of a CYP3A-like protein in the microsomes of these tissues, but, in addition, a immunoreactive protein with this antibody was also observed in the heart microsomes, suggesting the presence of other CYP3A isoforms in this fish. Accordingly, the southern blot analysis of genomic DNA indicated that multiple CYP 3As may be present in sea bass. All attempts to induce 6beta-testosterone hydroxylase, as a marker of CYP3A79, by dexametasone, 17beta-estradiol, pregnenolone 16alpha-carbonitrile, corticosterone, clotrimazole, and dehydroepiandrosterone failed. On the contrary, the administration of 17beta-estradiol, pregnenolone 16alpha-carbonitrile, and corticosterone strongly inhibited this activity and, in parallel, reduced the expression of CYP3A79 transcript. Thus, the sea bass CYP3A79 appears to be resistant to induction, suggesting that this enzyme and likely other CYP3As are regulated differently compared to those of mammals.

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“…The concentration of metabolites was determined by the ratio between respective metabolite and corticosterone (internal standard) peak areas, and the calibration curves obtained with synthetic testosterone derivatives. 40,41 The associated CYP isoforms are: 6␣ (CYP2A1, CYP2B1), 6␤ (CYP3A), and 16␣ (CYP2B9). 42 …”

Section: Testosterone Hydroxylase Activitymentioning

confidence: 99%

Bile acid structure and selective modulation of murine hepatic cytochrome P450-linked enzymes

et al. 1999

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Genetically engineered V79 chinese hamster cell expression of purified cytochrome P‐450iib1 monooxygenase activity

Cited by 61 publications

References 35 publications

Effects of dioxane on cytochrome P450 enzymes in liver, kidney, lung and nasal mucosa of rat

Effects of dioxane on cytochrome P450 enzymes in liver, kidney, lung and nasal mucosa of rat

Cloning, tissue expression, and inducibility of CYP 3A79 from sea bass (Dicentrarchus labrax)

Bile acid structure and selective modulation of murine hepatic cytochrome P450-linked enzymes

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