Pesticide, estrogen cause abnormal growth in rats

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Pesticide, estrogen cause abnormal growth in rats

Last Updated: 2002-06-20 10:00:48 -0400 (Reuters Health)

By Schorr

SAN FRANCISCO (Reuters Health) - Male laboratory animals exposed to a

plant-derived estrogen-like chemical and a common pesticide developed

abnormal excess breast tissue, researchers reported here Wednesday at

the annual meeting of the Endocrine Society.

" The combination of those compounds are able to change the developmental

course of the offspring, " said Dr. Li You, a scientist at CIIT Centers

for Health Research, a research organization in Research Triangle Park,

North Carolina.

You presented findings from a study in which pregnant and lactating

rodents were exposed to genistein, a naturally occurring chemical

present in plants such as soybeans that mimics the effects of the

hormone estrogen.

Researchers also exposed the animals to high levels of methoxychlor, a

commonly used insecticide and pesticide that farm workers and gardeners

often come in contact with. After birth, the animals were exposed to

both compounds for an additional 3 months, after which researchers

conducted a genetic analysis of their mammary gland tissue.

You reported that the female rats exposed in utero to the mixture of

chemicals went through puberty earlier, on average, while the male rats

similarly exposed went through puberty later than normal.

In addition, the male rats developed mammary glands similar to those

seen in female rats in early pregnancy. You also conducted genetic

testing and found that the chemicals alone and together altered the

expression of certain genes in the mammary tissues.

" We are still going through analysis, " he noted. " But by using genomic

type of approach, we will be able to examine genes in coordination of

the response of the animal to environmental factors, which would not be

possible without genomic tools. "

You said the study may point to how compounds in a normal diet could

alter the body's response to synthetic chemicals such as methoxychlor.

However, he noted, the rats received levels of exposure to the pesticide

and estrogen at higher levels than humans would be likely to encounter.

This type of research may point to one potential cause of the abnormal

development of increased breast tissue among men, the cause of which is

unknown in 30% of patients, noted Endocrine Society President Dr.

Crowley.