PNNL-13501 - Pacific Northwest National Laboratory

Study Control Number: PN00039/1446
Endocrine Disruption in the Built Environment
Larry E. Anderson, James E. Morris, Lyle B. Sasser
Spectrum restricted and daylight/night lighting in the built environment may alter natural neuroendocrine rhythms and
developmental processes. This project is designed to address the issue of possible endocrine disruption and changes in
long-term health by evaluating the influence of lighting changes on the endocrine system.
Project Description
Differences in spectral irradiance and intensity are known
to affect circadian response in humans in a laboratory.
Preliminary data from our laboratory suggests that altered
lighting may have more serious consequences.
Continuous light was observed to greatly accelerate
development of mammary tissue in rats. The potential for
environmental pollutants to alter endocrine function,
resulting in a variety of adverse health effects, has
become a high visibility environmental issue. This
project was devoted to investigating changes in tissue
morphology and in hormone levels, associated with
mammary tissue development, from altered timing of
light exposure. The expected outcome of this project was
focused on the effects of light on the endocrine system,
specifically, the effects of altered light (timing) on
hormone levels in an animal model.
Introduction
Life in industrialized societies is primarily life inside
buildings. Lighting in the built environment is quite
different from sunlight in intensity, spectral content, and
timing over the 24-hour daily period. Sunlight maintains
a 24-hour rhythm of endocrine function, including
melatonin release, as well as a host of other physiological
rhythms that are essential in the developmental processes.
Whether changes in the lighting environment have an
impact on environmental health issues, such as the rise in
breast and prostate cancer incidence, or altered childhood
development, is not known. However, a biological
rationale exists for potential endocrine disruptive effects
on disease through, for example, changes in melatonin
and impacts on estrogen homeostasis.
Approach
This study was designed to investigate the effects of light
exposure (constant, 24 hours per day) on mammary tissue
development. Experiments in rats were conducted to
examine both the endocrine (hormonal) responses and
morphological alterations in development. Normally,
under a 12:12 light-dark cycle, female rats first begin
estrus at 32 to 35 days of age. As the mammary gland
develops, terminal end buds begin to appear and
subsequently evolve into alveolar buds and eventually
into terminal ducts. This occurs from 40 to 60 days of
age, with maximum development activity at ages 40 to
46 days. The alveolar buds evolve into lobules of type 1,
which are more highly differentiated structures than
terminal end buds, terminal ducts, or alreolor buds, but do
not produce milk. Based on early work, we anticipate
profound changes in development of the mammary
epithelial tissue in the direction of a more rapid
development under constant lighting. In follow-up, we
determined levels of a key hormone (prolactin) in the
mammary tissue as well as the morphological staging of
development under the altered lighting scheme.
Results and Accomplishments
The proposed study was conducted where animals were
either exposed to a normal light cycle (12:12 light/dark)
or constant light (24 hour light) during the day. The
exposures occurred from birth through young adulthood
(approximately 60 days of age). Preliminary evidence
indicated a pronounced enhancement of mammary tissue
development in constant light-exposed rats; even to the
production of lactation in non-pregnant animals. The
main experiment was delayed until late in the fiscal year.
Tissues were sent to Dr. Irma Russo, Chief of Molecular
Endrocrinology, at the Fox Chase Cancer Center
(Philadelphia) where the morphology of the mammary
tissue is being examined and quantified. Prolactin levels
in the various tissues are also in the process of being
measured in our laboratory. To date, the exposure code
has not been broken, so specific results cannot be
presented until the assays are completed. In all,
approximately 50 animals per lighted condition were used
in the study and tissues from the animals were examined
at 3 different time points throughout early development.
Biosciences and Biotechnology 69