2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) Increases Release of Luteinizing Hormone and Follicle-Stimulating Hormone from the Pituitary of Immature Female Ratsin Vivoandin Vitro

摘要: Abstract Recent findings that serum levels of luteinizing hormone (LH) and follicle-stimulating (FSH) were dramatically increased in weanling female Sprague–Dawley (S–D) rats treated with 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD) prompted a more detailed study to define the effect investigate its mechanism(s). Dose–response time–course studies performed vivo. Single doses (0.03–30 μg/kg) TCDD administered orally by gastric intubation 22-day-old rats. Control animals received vehicle (corn oil) only, whereas naive controls an empty syringe. Trunk blood was collected after decapitation at various time points during subsequent 72 hr. Concentrations LH FSH determined radioimmunoassays (RIA). Two distinct peaks both hormones detected. The first, 1 hr, appeared be nonspecific response as it present control TCDD-treated animals, but not animals. second peak, 24 occurred only dosed TCDD. Gonadotropin these dose-dependently elevated. ED50 about 5 μg/kg maximum elevation 15- 20-fold for FSH, respectively. Subsequently, vitro conducted cultured pituitary halves primary cell cultures exposed gonadotropin releasing (GnRH) and/or amount released into media measured RIA. caused dose-dependent release from 0.1 n m . This abolished calcium-free medium attenuated GnRH antagonist. Further cultures. Although cells responded very well, no up 100 on gonadotropins results suggest induces brief immature is least partially due pituitary. Increased result treatment depends action calcium does occur via activation receptors. However, culture do respond gonadotropins, suggesting mediated factor culture.