Wildlife as models for the study of how mixtures, low doses, and
the embryonic environment modulate the action of endocrine-disrupting
chemicals
D. Crews, O. Putz, P. Thomas, T. Hayes, and K. Howdeshell
Institute of Behavioral Neuroendocrinology, University
of Texas at Austin, Austin, TX 78712, USA;
Marine Science Institute, University of Texas at Austin, 750 Channel
View Drive, Port Aransas, TX 78373, USA;
Department of Integrative Biology, University of California, Berkeley,
3060 Valley Life Sciences Building #3140, Berkeley, CA 94720-3140, USA;
Division of Biological Sciences, University of Missouri, 105 Lefevre
Hall, Columbia, MO 65211-6190, USA
Abstract: This paper will review briefly the use of wildlife
as models in the study of how mixtures, low doses, and the embryonic
environment modulate the action of endocrine active substances (EASs).
In so doing it will show how the issue of low dosages must be considered
within the context of mixtures present in the environment and the endocrine
background of the exposed individual. That is, in nature, EASs usually
are found in mixtures in which the constituent parts are in concentrations
well below their no observed adverse effect level (NOAEL) as determined
in single compound studies in the laboratory. In addition, exposure
always occurs on organisms in various endocrine states. Thus, the issue
of mixtures and dosages must always be considered within the context
of the endocrine background. Finally, the effects of exposure are passed
down through the generations. The question of exposure then at the level
of the individual becomes very complicated, as it must take into account
that at every life stage, the naturally occurring endocrine milieu of
the organism (or tissue), any EAS burden inherited from the mother or
built up over the individual's life, and the social environment in which
the individual develops and interacts as an adult, will influence the
response to acute exposure.
*Report from a SCOPE/IUPAC project: Implication of
Endocrine Active Substances for Human and Wildlife (J. Miyamoto and
J.Burger, editors). Other reports are published in this issue,
pp. 1617-2615.