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MAMMARY GLAND DEVELOPMENT: EARLY LIFE EFFECTS FROM THE ENVIRONMENT
Citation:
Fenton, S E. MAMMARY GLAND DEVELOPMENT: EARLY LIFE EFFECTS FROM THE ENVIRONMENT. Presented at Society of Toxicology, Salt Lake City, UT, March 09 - 13, 2003.
Description:
Mammary Gland Development: Early Life Effects from the Environment
S.E. Fenton. Reproductive Toxicology Division, National Health and Environmental Effects Laboratory, ORD, U.S. EPA, Research Triangle Park, NC 27711.
As signs of precocious puberty in girls reach the earliest mean age in history, many scientists are exploring the environment as a contributing factor. Accidental exposure to environmental toxicants and precocious use of estrogen or placental-protein containing hair care and beauty aid products have been suggested to alter the mean age at which groups of girls begin to show signs of puberty. An early sign of puberty includes breast development, in addition to other physical changes, during those years preceding the completion of puberty. Development of the woman's breast and the rodent mammary gland follow a similar timing in relationship to puberty. Animal models prove useful in exploring effects of early life exposure to environmental contaminants on development of reproductive tissues including the mammary gland. For example, EPA scientists are developing and validating pubertal and in utero/lactational protocols using rodent models, for initial screening and testing of environmental contaminants. Specifically, these protocols suggest examination of age at puberty, reproductive tissue development, endocrine hormone concentrations and growth rate of rodents exposed to endocrine disrupting compounds (EDCs). Our laboratory's focus is on development of mammary tissue prior to and during puberty in rat offspring exposed to EDCs during late gestation, a critical time in the outgrowth of mammary epithelia. Rapid mammary epithelial development begins prior to the emergence of regular estrous cycles in rodents and is completed shortly after that time, a progression similar to that found in humans. The timing of breast development and menses in young women is considered an important indicator of adult breast cancer risk, and recent studies in rodents are demonstrating that timing of the developed mammary gland and associated pubertal indicators are also indicative of susceptibility to carcinogen exposure and mammary tumor formation. Preliminary evidence indicates that the timing of mammary epithelial development can be altered by various EDCs, with compounds such as nonylphenol accelerating the pace and others (i.e., dioxin) delaying differentiation of the tissue. We have also begun to examine the mode of action(s) by which mammary gland development and other pubertal indicators are modulated by individual EDCs. Our studies and others could provide some foundation upon which hypothesis-driven longitudinal studies investigating environmental exposures and their affects on pubertal age can be designed and tested in young women. (This is an abstract of a proposed presentation and does not necessarily reflect EPA policy)