Effects of atrazine on metamorphosis, growth, laryngeal and gonadal development, aromatase activity, and sex steroid concentrations in Xenopus laevis.

African clawed frogs (Xenopus laevis) were exposed to one of eight nominal waterborne concentrations including 0, 0.1, 1.0, 10, or 25 microg/L atrazine, 0.005% ethanol (EtOH), or 0.1mg/L estradiol (E2) or dihydrotestosterone (DHT) containing 0.005% EtOH. Frogs were exposed from 72 h posthatch until 2--3 months postmetamorphosis via a 3-day static renewal exposure regimen. Atrazine at concentrations between 0.1 and 25 microg/L did not significantly affect mortality, growth, gonad development, laryngeal muscle size, or aromatase activity in juvenile X. laevis. Male frogs exposed to 1.0 microg/L atrazine had lower E2 levels compared to controls, but this response was not consistent among other concentrations of atrazine. Male and female frogs exposed to DHT had larger laryngeal dilator muscle areas compared to controls. E2-exposed female frogs had decreased gonadal aromatase activity, and E2-exposed male frogs had statistically greater plasma concentrations of E2 compared to controls.