Exposure of Adult Female Mice to Low Doses of di(2-ethylhexyl) Phthalate Alone or in an Environmental Phthalate Mixture: Evaluation of Reproductive Behavior and Underlying Neural Mechanisms

BACKGROUND: We have previously shown that adult male mice exposure to low doses of an ubiquitous endocrine disruptor, di(2-ethylhexyl) phthalate (DEHP), alters courtship behavior. OBJECTIVE: The effects of adult exposure to low doses of DEHP alone or in an environmental phthalate mixture on estrous cyclicity, reproductive behavior, and underlying neural structures were analyzed in female mice. METHODS: Two-month-old C57BL/6J females were exposed orally for 6 wk to DEHP alone (0, 5 or 50 lg/kg/d) or to DEHP (5 lg/kg/d) in a phthalate mixture. Estrous cyclicity was analyzed in intact mice, and behavior [lordosis, olfactory preference, partner preference, ability to stimulate male ultrasonic vocalizations (USVs)] was measured in ovariectomized mice primed with estradiol and progesterone. Immunohistochemical studies were conducted in the neural structures involved in behavior for estrogen receptor (ER) a and progesterone receptor (PR). RESULTS: Exposure to DEHP alone or in mixture lengthened the estrous cycle duration, with a shorter proestrus and longer estrus and metestrus stages. Under normalized hormonal levels, females exposed to DEHP alone or in mixture exhibited altered olfactory preference. A lower lordosis behavior and ability to attract and stimulate male emission of courtship USVs was observed, probably due to modifications of pheromonal emission in exposed females. The behavioral alterations were associated with a lower number of PR-expressing neurons, without changes in ERa, in the neural circuitry underlying sexual behavior. The majority of effects observed was comparable between the two DEHP doses and were driven by DEHP in the mixture. CONCLUSIONS: Exposure to environmental doses of DEHP alone or in mixture altered several components of female sexual behavior in mice, probably through selective disruption of neural PR signaling. Together with the previously reported vulnerability of male mice, this finding suggests a major impact of exposure to phthalates on sexual reproduction, including in other species with similar neural regulatory processes.

Automated summary

Exposure to environmental doses of DEHP alone or in mixture altered several components of female sexual behavior in mice, probably through selective disruption of neural PR signaling. The findings suggest a major impact of exposure to phthalates on sexual reproduction, including in other species with similar neural regulatory processes.