Chemical in soy alters reproductive organs in male rats

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Chemical in soy alters reproductive organs in male rats

Public release date: 10-Mar-2003

 

Contact: Jessica Collins

jcolli31

410-516-4570

Johns Hopkins Medical Institutions

 

Chemical in soy alters reproductive organs in male rats

 

Researchers at the Johns Hopkins Children's Center and the Johns Hopkins

Bloomberg School of Public Health report that male rats whose mothers were

fed diets containing genistein, a chemical found in soybeans, developed

abnormal reproductive organs and experienced sexual dysfunction as adults.

While these findings do not indicate that genistein has a similar effect in

humans, researchers say the increasing popularity of soy and soy-based

foods, such as tofu and some infant formulas, may warrant further research

to determine if genistein exposure in the womb and during breast-feeding

influences human reproductive development.

In the study, described in the April issue of the Journal of Urology,

pregnant female rats were randomly assigned to one of three regimens: a

genistein-free diet, a diet supplemented with a low dose of genistein, and a

diet with a high dose of genistein.

Male offspring were exposed to genistein indirectly through maternal

consumption during pregnancy and lactation.

When the genistein-exposed offspring matured, researchers found the males

had smaller testes and a larger prostate gland compared to unexposed rats.

Although their sperm counts were normal, exposed adult males had lower

testosterone levels and were also less likely to ejaculate when presented

with the opportunity to mate with a female.

" The effects of genistein continued long after the rats were exposed,

leading us to believe that exposure to this plant-derived estrogen during

reproductive development can have long-term detrimental effects in males, "

said the study's lead author, Amy B. Wisniewski, Ph.D., a researcher at the

Johns Hopkins Children's Center.

" Genistein may act as an estrogen or an anti-androgen, blocking the function

of endogenous androgens - the sex hormones necessary for males to develop a

normal reproductive system - and ultimately leading to the reproductive

abnormalities and sexual dysfunction we saw in the exposed rats, " added

study co-author Sabra L. Klein, Ph.D., of the School of Public Health.

" However, additional research is needed to determine if this is the case. "

Whether the long-term effects of genistein on the reproductive development

of male rats are caused by exposure during gestation, lactation, or both

also requires further investigation, Wisniewski said.

The study was funded by The Brady Urological Institute of The Johns Hopkins

Hospital. In addition to Wisniewski and Klein, other co-authors include John

P. Gearhart, M.D., and Yegappan Lakshmanan, M.D., of the Johns Hopkins

Children's Center and The Brady Urological Institute.

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Media Contacts:

Jessica Collins, Children's Center

410-516-4570

E-mail: jcolli31

Tim Parsons

Bloomberg School of Public Health

410-955-7619

E-mail: tmparson