A dose-response study following in utero and lactational exposure to di-(2-ethylhexyl)-phthalate (DEHP): non-monotonic dose-response and low dose effects on rat brain aromatase activity

Toxicology. 2006 Oct 29;227(3):185-92. doi: 10.1016/j.tox.2006.07.022. Epub 2006 Aug 1.

Abstract

Di-(2-ethylhexyl)-phthalate (DEHP) is a commonly used plasticizer which can act as an endocrine disruptor. It has been suggested that in addition to its antiandrogenic effects, DEHP may interfere with estrogen metabolism through suppression of aromatase enzyme activity. This enzyme catalyzes the conversion of testosterone to estradiol and plays a critical role in brain sexual differentiation. We investigated the effects of two wide ranges of DEHP doses on brain aromatase activity of male and female rat offspring. Wistar rat dams were treated daily with DEHP and peanut oil (control) by gavage from gestation day 6 to lactation day 21 at doses of 0.015, 0.045, 0.135, 0.405 and 1.215mgDEHP/kgbodyweight(bw)/day (low doses) and at 5, 15, 45, 135 and 405mgDEHP/kgbw/day (high doses). Aromatase activity was determined in hypothalamic/preoptic area (HPOA) brain sections from male and female pups on postnatal days (PNDs) 1 and 22. In males on PND 1, aromatase activity was inhibited at low doses and increased at high doses resulting in a non-monotonic dose-response profile which resembled a J-shaped curve. Inhibition was statistically significant at 0.135 and 0.405mgDEHP/kg/day, while increased activity was observed at 15, 45 and 405mg/kg/day. In contrast to findings on PND 1, aromatase activity at weaning (PND 22) was more affected in females than in males. An increase in aromatase activity was observed at only one dose in males (0.405mg/kg/day) while an increase in activity was observed at all doses in the females except for 0.045 and 5mgDEHP/kg/day. Overall, these results indicate that males and females respond differently to DEHP not only in regard to the age at which effects are manifested, but also in the shape of the dose-response curve. To our knowledge, this is the first study to report biological effects of DEHP at doses that overlap with the estimated exposure of the general human population.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age Factors
  • Animals
  • Aromatase / metabolism*
  • Brain / drug effects
  • Brain / enzymology*
  • Diethylhexyl Phthalate / pharmacokinetics
  • Diethylhexyl Phthalate / toxicity*
  • Dose-Response Relationship, Drug
  • Endocrine Disruptors / pharmacokinetics
  • Endocrine Disruptors / toxicity*
  • Female
  • Lactation*
  • Male
  • Pregnancy
  • Prenatal Exposure Delayed Effects / chemically induced
  • Prenatal Exposure Delayed Effects / enzymology*
  • Prenatal Exposure Delayed Effects / physiopathology
  • Rats
  • Sex Differentiation / drug effects

Substances

  • Endocrine Disruptors
  • Diethylhexyl Phthalate
  • Aromatase