Guidelines for Canadian Drinking Water Quality

We tested some resin-based composites used in dentistry for their estrogenic activity. A sealant based on bisphenol-A diglycidylether methacrylate (bis-GMA) increased cell yields, progesterone receptor expression, and pS2 secretion in human estrogen-target, serum-sensitive MCF7 breast cancer cells. Estrogenicity was due to bisphenol-A and bisphenol-A dimethacrylate, monomers found in the base paste of the dental sealant and identified by mass spectrometry. Samples of saliva from 18 subjects treated with 50 mg of a bis-GMA-based sealant applied on their molars were collected 1 hr before and after treatment. Bisphenol-A (range 90-931 micrograms) was identified only in saliva collected during a 1-hr period after treatment. The use of bis-GMA-based resins in dentistry, and particularly the use of sealants in children, appears to contribute to human exposure to xenoestrogens.

Estrogenicity of resin-based composites and sealants used in dentistry.

Molecular, clinical, and environmental toxicolog , Molecular, clinical, and environmental toxicolog , کتابخانه دیجیتال جندی شاپور اهواز

Molecular, Clinical and Environmental Toxicology

Background The authors critically surveyed research dealing with the release of resin components from dental composites and the potential of these agents to mimic or disrupt estrogenic cell responses. Types of Studies Reviewed The studies reviewed included those on synthetic methods used to make bisphenol A glycidyl methacrylate, or BIS-GMA, and the biological effects of this resin in cell culture and animals. The estrogenic effect of bisphenol A was targeted because bisphenol A is present as an impurity in some resins (BIS-GMA) and as a degradation product from other resins (bisphenol A dimethacrylate, or BIS-DMA). Results The outcomes of this review revealed that short-term administration of BIS-GMA and/or bisphenol A in animals or cell cultures can induce changes in estrogen-sensitive organs or cells. However, considering the dosages and routes of administration and the modest response of estrogen-sensitive target organs, the authors conclude that the short-term risk of estrogenic effects from treatments using bisphenol A–based resins is insignificant. Long-term effects need to be investigated further. Clinical Implications Commonly used dental resins should not be of concern to the general public; however, pharmacological evaluation of dental materials is needed to ensure biologically safe and therapeutically effective substances.

Bis-gma–based resins in dentistry: are they safe?

Aims: To evaluate effects of exposure to bisphenol A diglycidyl ether (BADGE) on urinary excretion of bisphenol A, and plasma gonadotrophic hormones and testosterone in male epoxy resin sprayers. 

Methods: Cross sectional study of 42 workers whose job was to spray epoxy resin hardening agents including BADGE and mixed organic solvents, and 42 matched control workers without BADGE use in the same machine plants. 

Results: Concentrations of urinary bisphenol A were higher in the epoxy resin sprayers (median 1.06 µmol/mol creatinine) compared with the controls (median 0.52 µmol/mol creatinine). Urinary metabolite concentrations of organic solvents used were all higher in the epoxy resin workers compared with the controls. Endocrinological examination showed different concentrations of follicle stimulating hormone (FSH) between the epoxy sprayers (median 5.3 mIU/ml) and the controls (median 7.6 mIU/ml). FSH showed a mild correlation with urinary bisphenol A, but not with the metabolites of organic solvents. Luteinising hormone and free testosterone concentrations did not differ between the two groups. 

Conclusion: BADGE may generate bisphenol A endogenously. Results suggest that bisphenol A may disrupt secretion of gonadotrophic hormones in men. The clinical significance of endocrine disrupting effects by bisphenol A should be further investigated in male workers exposed to bisphenol A.

https://oem.bmj.com/content/oemed/59/9/625.full.pdf

Urinary bisphenol A and plasma hormone concentrations in male workers exposed to bisphenol A diglycidyl ether and mixed organic solvents.

1. (Z)-1,3-Dichloro[2-14C]propene([14C](Z)-DCP) when dosed orally to rats gave 82-84% of the radioactivity in the urine 24 h after treatment. Most of this 14C (92%) was present as N-acetyl-S-((Z)-3-chloroprop-2-enyl)cysteine ((Z)-DCP mercapturic acid).2. When (Z)-DCP was incubated with glutathione and rat liver cytosol (containing glutathione S-alkyl transferase), very rapid loss of (Z)-DCP was observed. The product of this reaction was S-[(Z)-3-chloroprop-2-enyl)]glutathione.

Glutathione conjugation in the detoxication of (Z)-1,3-dichloropropene (a component of the nematocide D-D) in the rat.

1. The major metabolic transformation of orally ingested 14C-DGEBPA is by hydrolytic ring-opening of the two epoxide rings to form diols. This metabolite (the bis-diol of DGEBPA) is excreted in both free and conjugated forms and is further metabolized to various carboxylic acids, including two containing a methylsulphonyl moiety. 2. The product of oxidative dealkylation either of DGEBPA (with concomitant formation of glycidaldehyde) or of the bis-diol of DGEBPA (with concomitant formation of glyceraldehyde) is excreted in both free and conjugated forms in amounts representing 5% of the dose. 3. The high activity of epoxide hydratase towards DGEBPA suggests that glyceraldehyde and not glycidaldehyde is formed in vivo. 4. Hepatic epoxide hydratase activity towards DGEBPA measured in vitro decreased in the order rabbit greater than mouse greater than rat. 5. Two discrete epoxide hydratases are present in large amounts in the mouse. One is membrane-bound in the liver microsomal fraction and the other is a "soluble' enzyme located in the liver cytosol. This cytosolic enzyme was present in only very small amounts in the rat.

Metabolism of the epoxy resin component 2,2-bis[4-(2,3-epoxypropoxy)phenyl]propane, the diglycidyl ether of bisphenol A (DGEBPA) in the mouse. Part II. Identification of metabolites in urine and faeces following a single oral dose of 14C-DGEBPA.

1. 14C-DGEBPA dermally applied to mice was only slowly eliminated in the faeces (20% dose) and urine (3%), as a mixture of metabolites, over three days. Most of the applied radioactivity (66% dose) was extracted from the application area and its covering foil.2. When 14C-DGEBPA was given orally to mice it was rapidly excreted; 80% of the administered 14C was eliminated in the faeces and 11% in the urine 0-3 days after a single oral dose.3. The urinary and faecal metabolite profiles derived from dermal application and oral dosing were essentially similar.

Metabolism of the epoxy resin component 2,2-bis[4](2,3]epoxypropoxy)phenyl]propane, the diglycidyl ether of bisphenol A (DGEBPA) in the mouse. Part I. A comparison of the fate of a single dermal application and of a single oral dose of 14C-DGEBPA.

Ethyl[14C]benzene hydroperoxide administered orally to female rats (30 mg/kg) is rapidly absorbed and metabolized. Most of the administered compound (81%) is eliminated in the 0-24 h urine. Major metabolites include mandelic acid (23%), hippuric acid (34%) and 1-phenylethyl glucuronide (4%). Ethyl[14C]benzene is metabolized via 1-phenylethanol to the same mixture of metabolites as obtained with the hydroperoxide. Biotransformations of the hydroperoxide and their likely biochemical mechanisms are discussed.

The metabolism of ethylbenzene hydroperoxide in the rat

1. A major route of metabolism of the methylmercaptotriazine herbicide cyanatryn involves S-oxygenation.2. The S-oxide reacts spontaneously with glutathione affording a conjugate, which is eliminated in the bile, and a mercapturic acid which is eliminated in the urine.3. A small proportion of the administered dose was covalently bound to a component of the blood, probably haemoglobin. This was shown to be dependent on the formation of the S-oxide and on the species of animal studied.4. No reactivity of the S-oxide towards DNA in vivo, or in vitro could be demonstrated.

The metabolic fate of a herbicidal methylmercapto-s-triazine (cyanatryn) in the rat.

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