Localization of diethylstilbestrol metabolites in the mouse genital tract.
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
M Metzler
Publications and source records attributed to M Metzler.
Excretion pattern and metabolism of hexachlorobutadiene in rats. Evidence for metabolic activation by conjugation reactions.
Excretion, covalent binding and metabolism of hexachloro-1,3-butadiene (HCBD), a nephrotoxic and nephrocarcinogenic compound, have been studied in female rats. Seventy-two hours after administration of a single oral dose of 1 mg/kg [14C]HCBD, 5.3% of the dose were exhaled as unchanged HCBD and 76.3% were metabolized and excreted in urine and feces or exhaled as 14CO2. After a 50 mg/kg dose of [14C]HCBD, the amount of exhaled parent compound was nearly unchanged at 5.4%. At the higher dose the gastro-intestinal absorption of HCBD appeared to be saturated with the result that unchanged HCBD constituted the major portion of the 69% radioactivity eliminated. Covalent binding to proteins in kidney and liver agreed well with the organ-specific toxicity of HCBD: binding was higher in the kidney, independent of the dose. It increased significantly when the rats were pretreated with phenobarbital, an inducer of monooxygenases; it decreased when the inhibitor piperonyl butoxide was given. Urinary radioactivity in 24 hr urine was separated by column chromatography into four fractions. High performance liquid chromatography, radio gas chromatography and gas chromatography/mass spectrometry were used for further separation and identification. Two major metabolites were identified as pentachlorobutadiene methylthio ether and pentachlorobutadiene carboxymethylthio ether. Their formation is plausibly explained via glutathione conjugation, which appears to be the first step in HCBD metabolism. The mechanism of the conjugation at the olefinic double bond of HCBD is explained by an addition-elimination reaction. This pathway, which appears to lead to a destabilization of the HCBD molecule, could explain the distinct nephrotoxic effects of HCBD.
Animals↗
Morphological transformation of Syrian hamster embryo fibroblasts by the anabolic agent trenbolone.
Trenbolone (TBOH), a synthetic androgen used as an anabolic agent in livestock, has been tested for mutagenicity in the Salmonella assay, for covalent DNA-binding in vitro, for induction of unscheduled DNA synthesis in HeLa cells and Syrian hamster embryo (SHE) fibroblasts and for morphological transformation of SHE cells. While TBOH gave negative results in the assays for mutagenicity and DNA damage, it was clearly capable of transforming SHE cells in culture. The natural androgen testosterone did not transform these cells. Thus, TBOH appears to be a substance which can transform cells independent of its hormonal action and without grossly damaging DNA.
Animals↗
Oxidative and conjugative metabolism of diethylstilbestrol by rabbit preimplantation embryos.
Five- and six-day-old rabbit preimplantation embryos were found to be capable of metabolizing [3H]diethylstilbestrol (DES) in vitro. Based on the analysis of the metabolites formed during a 24-hr incubation period we conclude that these early stage embryos do have active monooxygenase and conjugative activity. The monooxygenase seems to be specific to this early stage of embryonic development.
Animals↗
Covalent binding of diethylstilbestrol to microsomal protein in vitro correlates with the organotropism of its carcinogenicity.
[14C]Diethylstilbestrol (DES) was incubated in vitro with liver and kidney microsomes from male and female hamsters and rats, and the extent of non-extractable binding of radioactivity to microsomal protein was determined. Binding to microsomes from male hamster kidney, which is a target organ for DES carcinogenicity in vivo, was found to be 5-10 times higher than binding to microsomes from non-target tissues. Pretreatment with phenobarbital led to a marked increase in binding of DES to kidney microsomes but not to liver microsomes from female hamsters and male and female rats. The correlations of in vitro covalent binding with organ susceptibility implies a role for metabolic activation of DES in the mechanism of its carcinogenicity.
Animals↗
Dearylation and other cleavage reactions of diethylstilbestrol: novel oxidative pathways mediated by peroxidases.
Oxidation of diethylstilbestrol (I) by peroxidases from horseradish or mouse uterus in the presence of H2O2 in vitro leads to Z,Z-dienestrol (II) and to a number of cleavage products, five of which were identified by g.l.c.-mass spectrometry and comparison with authentic reference compounds as 4-hydroxybenzoic acid (III), 4'-hydroxypropiophenone (IV), 1'(4'-hydroxyphenyl)-propan-1-on-2-ol (V), 1-(4'-hydroxyphenyl)-propan-1,2-dione (VI) and 3-(4'-hydroxyphenyl)-hex-2-en-4-one (VII). The formation of 3-(4'-hydroxyphenyl)-hex-2-en-4-one (VII) from diethylstilbestrol is the first reported example of a metabolic dearylation reaction. The amount of cleavage products depends on the excess of H2O2 used. The amount of H2O2 does not affect the extent of binding of diethylstilbestrol to DNA as mediated by peroxidases. The syntheses of V, VI and VII are described.
Animals↗
Novel metabolites of trichloroethylene through dechlorination reactions in rats, mice and humans.
The excretion and biotransformation of [14C]trichloroethylene (Tri) has been studied in female rats and mice. Seventy-two hours after a single oral dose of 200 mg/kg, rats exhaled 52% and mice 11% of the recovered radioactivity as unchanged Tri, and 1.9% and 6%, respectively, as 14CO2. Rats excreted 41.2% of the recovered radioactivity in the urine, in contrast to mice where urinary activity amounted to 76%. The isolation of urinary metabolites was accomplished by reversed-phase HPLC, using a water-methanol gradient. After chemical derivatization, a combination of radio-GC and GC/MS was used for identification. The metabolites identified in rat urine were: trichloroacetic acid (15.3%); trichloroethanol, free (11.7%) and as the glucuronide (61.9%); dichloroacetic acid (2.0%); oxalic acid (1.3%) and N-(hydroxyacetyl)-aminoethanol (HAAE) (7.2%). In mice, trichloroethanol (free and in several conjugated forms) is the main metabolite of Tri (94.3%), but small amounts of HAAE (4.1%) and oxalic acid (0.7%) are also excreted. Only traces of dichloro- and trichloroacetic acids were found in this species. In human male subjects, HAAE was also identified as a urinary metabolite of Tri after exposure of two volunteers to 200 ppm Tri for 6 hr. The identification of HAAE and oxalic acid as metabolites indicates hydrolytic dechlorination reactions in the metabolism of Tri.
Administration, Oral↗
Developmentally regulated plant genes: the nucleotide sequence of a wheat gliadin genomic clone.
Gliadins, the major wheat seed storage proteins, are encoded by a multigene family. Northern blot analysis shows that gliadin genes are transcribed in endosperm tissue into two classes of poly(A)+ mRNA, 1400 bases (class I) and 1600 bases (class II) in length. Using poly(A)+ RNA from developing wheat endosperm we constructed a cDNA library from which a number of clones coding for alpha/beta and gamma gliadins were identified by hybrid-selected mRNA translation and DNA sequencing. These cDNA clones were used as probes for the isolation of genomic gliadin clones from a wheat genomic library. One such genomic clone was characterized in detail and its DNA sequence determined. It contains a gene for a 33-kd alpha/beta gliadin protein (a 20 amino acid signal peptide and a 266 amino acid mature protein) which is very rich in glutamine (33.8%) and proline (15.4%). The gene sequence does not contain introns. A typical eukaryotic promoter sequence is present at -104 (relative to the translation initiation codon) and there are two normal polyadenylation signals 77 and 134 bases downstream from the translation termination codon. The coding sequence contains some internal sequence repetition, and is highly homologous to several alpha/beta gliadin cDNA clones. Homology to a gamma-gliadin cDNA clone is low, and there is no homology with known glutenin or zein cDNA sequences.
Amino Acid Sequence↗
Oxidative metabolites of diethylstilbestrol in the fetal Syrian golden hamster.
14C-Diethylstilbestrol was administered orally, intraperitoneally, and intrafetally to 15-day pregnant hamsters at a dose of 20 mg/kg body weight, and the radioactivity was determined in the fetus, placenta, and maternal liver after 6 hours. Significant amounts of radioactivity were found in these tissues in every case, indicating maternal-fetal and fetal-maternal transfer of diethylstilbestrol. Part of the radioactivity found in the tissues could not be extracted even after excessive washing. This implied the presence of reactive metabolites. In the fetal and placental extracts, eight oxidative metabolites of diethylstilbestrol were identified by mass fragmentography as hydroxy- and methoxy-derivatives of diethylstilbestrol, pseudodiethylstilbestrol, and dienestrol. The presence of oxidative metabolites in the hamster fetus and the covalent binding to tissue macromolecules are possibly associated with the fetotoxic effects of diethylstilbestrol.
Animals↗
Metabolism of stilbene estrogens and steroidal estrogens in relation to carcinogenicity.
The oxidative metabolism of diethylstilbestrol (DES) and 17 alpha-ethynyl estradiol, as examples of stilbene- and steroid-type estrogens, is discussed with respect to the formation of reactive intermediates. For DES, a genotoxic potential is implied by metabolic studies and positive effects in short-term tests for genetic damage. A particularly important pathway for DES carcinogenicity appears to be peroxidase-mediated oxidation. Although data for steroidal estrogens are more ambiguous, the available evidence suggests that metabolic activation by peroxidatic oxidation may also be of importance for this class of estrogens.
Animals↗
Peroxidase-mediated binding of diethylstilbestrol analogs to DNA in vitro: a possible role for a phenoxy radical.
In order to investigate the role of peroxidase-mediated metabolic activation in the mechanism of carcinogenicity of diethylstilbestrol (DES), a series of 14C-labelled analogs of DES was synthesized and their binding to DNA upon oxidation by peroxidases from horseradish or mouse uterus was studied in vitro. The compounds chosen for this study were the erythro and threo form of hexestrol (HES), the E,E- and Z,Z-isomer of dienestrol (DIES) and the mono- and dimethyl ether of DES. Non-extractable binding to DNA was observed for all compounds with at least one free hydroxyl group independent of the stilbene structure. The extent of binding was highest for the HES isomers and for E,E-DIES, whereas Z,Z-DIES and the monomethyl ether were bound to about the extent of DES. These findings imply that the formation of a phenoxy free radical is sufficient for non-extractable DNA binding and the stilbene structure is not required for peroxidase-mediated activation of DES.
Animals↗
Oxidative metabolites of the teratogen and transplacental carcinogen diethylstilbestrol in the fetal Syrian golden hamster.
14C-labelled diethylstilbestrol was administered orally, intraperitoneally, and intrafetally to 15-day pregnant hamsters and the radioactivity determined in the fetus, placenta, and maternal liver after six hours. Significant amounts of radioactivity were found in these tissues in every case, indicating maternal-fetal and fetal-maternal transfer of diethylstilbestrol. Part of the radioactivity found in the tissues could not be extracted even after excessive washing. This implied the presence of reactive metabolites. In the fetal and placental extracts, eight oxidative metabolites of diethylstilbestrol were identified by mass fragmentography as hydroxy- and methoxy-derivatives of diethylstilbestrol pseudo diethylstilbestrol, and dienestrol. The presence of oxidative metabolites in the hamster fetus and the covalent binding to tissue macromolecules are possibly associated with the fetotoxic effect of diethylstilbestrol.
Animals↗
Molecular structures of metabolites and analogues of diethylstilbestrol and their relationship to receptor binding and biological activity.
A series of indanyl derivatives of diethylstilbestrol (DES) have recently been identified as inv vivo metabolites of DES. These compounds are of interest because they possess effective uterine estrogen receptor-binding affinity but poor biological activity. The X-ray crystal structures of three of these derivatives were determined and their conformations were compared with those of estradiol and DES. The more active derivatives, indenestrol A (I) and indenestrol B (II) have nearly identical conformations, in which the overall molecule is highly planar, the phenyl ring is twisted out of the plane of the indene rings by approximately 30 degrees, and the distance between the hydroxyl groups is 11.6 A. In the least active derivative, idanestrol (III), the methyl, ethyl, and phenyl substituents were found to be in the same side of the indane ring so that the molecule is constrained to an L-shape. The crystallographically observed conformations of I, II, III, DES, and estradiol, their competative binding affinities, and their in vivo biological activities are consistent with the proposal that the steroid A-ring plays a dominant role in initiating receptor binding while the D-ring orientation relative to the A-ring has a more decisive influence upon activity. The reduction in estrogen receptor-binding affinity and associated reduced activity of III is almost certainly due to its L-shape conformation. The extended conformation of I and II in which both phenolic rings are exposed permitting ready access to both surfaces of either ring probably accounts for the ability of these derivatives to compete so successfully with estradiol for estrogen receptor binding. There are eight different ways in which the molecules of the racemic mixtures of I and II could initiate receptor binding. The reduced biological activity of I and II is probably due to the fact that not all eight binding orientations are compatible with eliciting estrogenic response. Comparison of the observed conformations of I, II, DES, and estradiol suggests that it is the alpha-ring of I and II that minics the steroid A-ring in receptor binding, and that two of the four possible alpha-ring/A-ring matches are most conducive to eliciting hormone activity.
Animals↗
Fibrinolytic response to trauma.
The fibrinolytic response to trauma was investigated in 23 patients. Patients were triaged upon arrival in the emergency center into three groups; group I-patients with significant trauma who maintained normal vital signs, had a good prognosis, and tolerated the trauma well (mean injury severity score 8, range 4 to 12); group II--patients with significant trauma and transient episodes of hypotension, hypoxia, or acidosis who recovered (mean injury severity score 22, range 9 to 38); and group III--patients with profound or continued hypoxia and hypotension who eventually died of the trauma (mean injury severity score 41, range 30 to 50). Serial measurements of prothrombin time, activated partial thromboplastin time, and platelet count; concentrations of fibrinogen, plasminogen, and fibrin degradation products; and assays of euglobulin fraction fibrinolytic activity on plasminogen-free and plasminogen-rich fibrin plates were obtained on all patients. Coagulation studies documented a trauma-related coagulopathy that correlated with the degree of trauma. Plasminogen concentrations were initially depressed in all three groups; however by 24 hours group III patients were noted to have significantly elevated plasminogen concentrations while group I and group II patients had normal plasminogen concentrations. Fibrinolytic activity measured on plasminogen-free and plasminogen-rich fibrin plates was initially increased in all three groups with group III patients demonstrating the greatest increase. Over the succeeding 14 hours fibrinolytic activity returned to baseline values in group I and group II patients while group III patients demonstrated no detectable fibrinolytic activity for the remainder of the study period. This absence of fibrinolytic activity and increase in plasminogen concentrations in group III patients is thought to be caused by depletion of the intravascular plasminogen activator with the subsequent development of a hypofibrinolytic state.
Blood Coagulation↗
Diethylstilbestrol metabolism by the fetal genital tract.
Oxidative metabolism of diethylstilbestrol (DES) was measured in both the male and female genital tracts of the fetal mouse in organ culture. The major oxidative metabolite formed was Z,Z-dienestrol, whose formation appeared to be time dependent in the isolated fetal genital tract of both sexes. This peroxidative metabolite, which has been previously linked to bioactivation of DES in adult target tissues, was not detected in the fetal liver cultures. In addition, fetal genital tracts were capable of O-methylation of DES. In fact, a new metabolite, 4'-O-methyl-DES, was formed in fetal genital tissues but not in liver cultures. On the other hand, conjugation of DES occurred extensively in the fetal liver and placenta but not in the fetal genital tissues; conjugated DES was found primarily in the media. Thus, the fetal genital tract, which is the primary target for the transplacental carcinogenicity of DES, has the capacity to metabolize this compound.
Animals↗
Role of metabolic activation in the transplacental carcinogenicity of diethylstilbestrol.
Metabolic studies have shown a variety of oxidative pathways in the biotransformation of the synthetic estrogen, diethylstilbestrol (DES). The metabolic intermediates are reactive electrophiles and bind covalently to proteins and nucleic acids. DES and some of its metabolites have proven to be genotoxic in several assays using mammalian cells. Oxidative metabolism of DES has also been shown in rodent fetuses and even in the ultimate target organ of DES transplacental carcinogenicity, the fetal genital tract. These findings imply that reactive metabolites may play a role in DES fetotoxicity, and several mechanisms accounting for the organotropism of DES transplacental carcinogenicity are proposed.
Animals↗
Oxidative metabolism of the synthetic estrogens hexestrol and dienestrol indicates reactive intermediates.
Explore the source record for details and available documents.
Animals↗
The tumor-inhibiting effect of diethylstilbestrol-3,4-oxide.
Diethylstilbestrol-3,4-oxide, (DES-3,4-oxide), one of the possible cancerogenic metabolites of the well-known estrogen diethylstilbestrol (DES), is a potential estrophilic cytostatic compound. It shows a very good affinity to the estrogen receptor. The uterotrophic activity determined in the mouse uterine weight bioassay is nearly identical with that of DES. Potential alkylating properties could neither be detected in the p-NBP test not in the prophage induction test. DES-3,4-oxide [0.01-1.0 mg/kg body weight (b. wt.)] markedly inhibited the growth of the DMBA-induced hormone-dependent mammary carcinoma of the SD rat, as well as the growth of a hormone-dependent postmenopausal (but not of a premenopausal) human mammary carcinoma serially transplanted in nude mice. However, DES-3,4-oxide had no significantly better effect on the DMBA-induced mammary carcinoma of the SD rat than DES.
9,10-Dimethyl-1,2-benzanthracene↗