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Published on: October 2, 2018
Atrazine disrupts the hypothalamic control of pituitary-ovarian function
R L Cooper1, T E Stoker, L Tyrey
1Endocrinology Branch, Reproductive Toxicology Division, National Health and Environmental Effects Research Laboratory, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA. Cooper.Ralph@epa.gov
Summary
Atrazine, a common herbicide, disrupts hormone regulation by affecting the hypothalamus in rats. This study shows atrazine alters luteinizing hormone and prolactin levels, with female rats being more sensitive.
Area of Science:
- Endocrinology
- Neuroscience
- Toxicology
Background:
- Chloro-S-triazine herbicides, including atrazine, are widely used in the US.
- Limited knowledge exists regarding their human health effects and mechanisms of action.
- Previous research indicated chlorotriazines disrupt ovarian cycle hormonal control.
Purpose of the Study:
- To investigate the hypothesis that herbicides disrupt endocrine function via the central nervous system.
- To evaluate the effects of atrazine on estrogen-induced luteinizing hormone (LH) and prolactin surges in rats.
- To determine the specific site of action (brain, pituitary, or both) for atrazine's endocrine-disrupting effects.
Main Methods:
- Ovariectomized Sprague-Dawley (SD) and Long-Evans hooded (LE) rats were treated with atrazine (50-300 mg/kg/day) for 1, 3, or 21 days.
- Estrogen-induced LH and prolactin surges were measured.
- Experiments involved pituitary autotransplants, GnRH challenges, and in vitro pituitary perifusion to pinpoint the site of action.
Main Results:
- A single dose of atrazine suppressed LH and prolactin surges in LE rats but not SD rats.
- Repeated atrazine administration suppressed hormone surges in both rat strains in a dose-dependent manner after 21 days.
- Experiments indicated that atrazine's effects are mediated via the hypothalamus, not the pituitary directly.
Conclusions:
- Atrazine alters serum LH and prolactin levels in female rats by affecting hypothalamic control.
- Long-Evans hooded rats exhibited greater sensitivity to atrazine's hormone-suppressive effects.
- These findings support the hypothesis that atrazine disrupts endocrine function through hypothalamic action.
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