Document Detail

Estrogenic isoflavones in rodent diets.
MedLine Citation:
PMID:  11869825     Owner:  NLM     Status:  MEDLINE    
Many rodent diets contain components such as soy isoflavones (daidzein and genistein) known to have estrogenic properties. The dietary background of phytoestrogens may modulate some responses to environmental estrogens when these compounds are tested in rodent bioassays. Thus, and since only few data were available on the phytoestrogen content of rodent diets commonly used in European laboratories, it was of interest to analyze the daidzein and genistein contents of our standard animal feeds. Isoflavone contents were determined in seven batches of rodent chow (from two suppliers in Germany, Altromin and Ssniff) by high-performance liquid chromatography, and also analyzed in six rodent diets from the United States. The soy-based rodent diets from Germany contained isoflavone (daidzein plus genistein) concentrations in the range of 0.3-0.55 mg/g feed. These isoflavone contents are similar to those analyzed in the US rodent diets, and similar to values reported by others, including one particular lot of feed (with 0.35 mg isoflavones per g) which produced a large uterotrophic response in immature ovariectomized rats [Environ. Health Perspect., 106 (1998) 369]. Coumestrol was found in a sample of commercial rabbit food at rather high levels (0.27 mg/g), but, this phytoestrogen was not detected (<1 microg/g feed) in any of the other samples we analyzed. The soy components in our rodent diet produce a measurable background of daidzein and genistein in blood of female DA/Han rats, total isoflavones (aglycone plus conjugates) ranging between 90 and 290 ng/ml plasma. The ovariectomized animals kept on this chow, showed no signs of estrogenization of the reproductive tract (uterus, vagina), and responded normally to (xeno-)estrogen administration in a uterotrophic assay [J. Steroid Biochem. Mol. Biol., 73 (2000) 1]. Moreover, ovariectomized Wistar rats on our standard rodent diet (Ssniff R/M H) had lower uterine weights than animals kept on the isoflavone-free (solvent extracted) chow; both groups of rats responded to genistein administration with an increase in uterine weights. These results suggest that--albeit the sensitivity of the rodent uterotrophic assay is not reduced by the use of a diet containing soy isoflavones at commonly encountered levels--attention should be given to a variable dietary phytoestrogen background.
Gisela H Degen; Petra Janning; Patrick Diel; Hermann M Bolt
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Toxicology letters     Volume:  128     ISSN:  0378-4274     ISO Abbreviation:  Toxicol. Lett.     Publication Date:  2002 Mar 
Date Detail:
Created Date:  2002-02-28     Completed Date:  2002-05-10     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  7709027     Medline TA:  Toxicol Lett     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  145-57     Citation Subset:  IM    
Institut für Arbeitsphysiologie an der Universität Dortmund, Ardeystr. 67, D-44139 Dortmund, Germany.
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MeSH Terms
Animal Feed / analysis*
Estrogens, Non-Steroidal / blood,  metabolism,  pharmacology*
Genistein / blood,  metabolism,  pharmacology*
Growth Inhibitors / blood,  metabolism,  pharmacology
Isoflavones / blood,  metabolism,  pharmacology*
Organ Size / drug effects
Plant Preparations
Rats, Wistar
Statistics, Nonparametric
Uterus / anatomy & histology,  drug effects*
Reg. No./Substance:
0/Estrogens, Non-Steroidal; 0/Growth Inhibitors; 0/Isoflavones; 0/Phytoestrogens; 0/Plant Preparations; 446-72-0/Genistein; 486-66-8/daidzein

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