Document Detail


2-Methoxyethanol metabolism, embryonic distribution, and macromolecular adduct formation in the rat: the effect of radiofrequency radiation-induced hyperthermia.
MedLine Citation:
PMID:  11397557     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Exposure of pregnant rats to the solvent 2-methoxyethanol (2ME) and radiofrequency (RF) radiation results in greater than additive fetal malformations (Nelson, B.K., Conover, D.L., Brightwell, W.S., Shaw, P.B., Werren, D.W., Edwards, R.M., Lary, J.M., 1991. Marked increase in the teratogenicity of the combined administration of the industrial solvent 2-methoxyethanol and radiofrequency radiation in rats. Teratology 43, 621-34; Nelson, B.K., Conover, D.L., Shaw, P.B., Werren, D.W., Edwards, R.M., Hoberman, A.M., 1994. Interactive developmental toxicity of radiofrequency radiation and 2-methoxyethanol in rats. Teratology 50, 275-93). The current study evaluated the metabolism of 14C-labeled 2ME and the distribution of methoxyacetic acid (MAA) in maternal and embryonic tissues of pregnant Sprague-Dawley rats either exposed to 10 MHz RF radiation or sham conditions. Additionally, adduct formation for both plasma and embryonic protein was tested as a possible biomarker for the observed 2ME/RF teratogenicity. Rats were administered [ethanol-1,2-(14)C]-2ME (150 mg/kg, 161 microCi/rat average) by gavage on gestation day 13 immediately before RF radiation sufficient to elevate body temperature to 42 degrees C for 30 min. Concurrent sham- and RF-exposed rats were sacrificed at 3, 6, 24 or 48 h for harvest of maternal blood, urine, embryos and extra-embryonic fluid. Tissues were either digested for determination of radioactivity or deproteinized with TCA and analyzed by HPLC for quantification of 2ME metabolites. Results show the presence of 2ME and seven metabolites, with the major metabolite, MAA, peaking at 6 h in the tissues tested. MAA, the proximal teratogen, was detectable in maternal serum, urine, embryo and extraembryonic fluid 48 h after dosing. Clearance of total body 14C was significantly reduced for the RF-exposed animals (P<0.05) for the 24-48 h period, but MAA values for serum, embryos and extraembryonic fluid were similar for both sham- and RF-exposed rats. Additionally, no difference was noted for 2ME metabolite profiles in urine or tissue for sham- or RF-exposed rats, thus eliminating an effect of RF radiation on MAA production as a possible explanation for the reported RF-2ME synergism. Subsequently, serum and embryo protein-bound adducts were evaluated by analysis of covalently bound radioactivity. Serum protein binding was significantly higher for sham than RF rats at 3- and 6-h - highest for sham rats at 6 h (519+/-95 microg as parent 2ME/g of protein) whereas RF serum values were highest at 24 h (266+/-79 microg/g protein). Embryonic protein binding was significantly higher for sham rats at 6 h, but binding was highest for both groups at 24 h (sham=229+/-71 microg/g, RF=185+/-48 microg/g). Formation of protein adducts after 2ME is thought to be related to levels of methoxyacetaldehyde, a reactive intermediate in the formation of MAA. These results suggest that no direct relationship exists for covalent binding in the embryo which would explain RF-2ME synergistic malformations. In comparison with urinary metabolites, the relatively slow elimination of adducted serum 2ME indicates that analysis of protein-bound concentrations could be a potential tool for long- term biomonitoring of worker exposure.
Authors:
K L Cheever; T F Swearengin; R M Edwards; B K Nelson; D W Werren; D L Conover; D G DeBord
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Toxicology letters     Volume:  122     ISSN:  0378-4274     ISO Abbreviation:  Toxicol. Lett.     Publication Date:  2001 May 
Date Detail:
Created Date:  2001-06-08     Completed Date:  2001-07-26     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  7709027     Medline TA:  Toxicol Lett     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  53-67     Citation Subset:  IM    
Affiliation:
DHHS/PHS, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Division of Applied Research and Technology, 4676 Columbia Parkway, Cincinnati, OH 45226, USA. klc1@cdc.gov
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MeSH Terms
Descriptor/Qualifier:
Acetic Acids / pharmacokinetics,  toxicity
Animals
Biological Markers / blood
Chromatography, High Pressure Liquid
Embryo, Mammalian / drug effects,  metabolism*,  radiation effects
Ethylene Glycols / pharmacokinetics*,  toxicity
Female
Fever / etiology
Gas Chromatography-Mass Spectrometry
Kinetics
Macromolecular Substances
Male
Pregnancy
Radio Waves / adverse effects
Rats
Rats, Sprague-Dawley
Teratogens / pharmacokinetics*,  toxicity
Chemical
Reg. No./Substance:
0/Acetic Acids; 0/Biological Markers; 0/Ethylene Glycols; 0/Macromolecular Substances; 0/Teratogens; 109-86-4/methyl cellosolve; 625-45-6/methoxyacetic acid

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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