Department of Animal Physiology and Endocrinology, Agricultural University in Krakow, Al. Mickiewicza 24/28, 30-059 Krakow, Poland.
Toxicol Lett. 2011 Aug 28;205(2):190-5. doi: 10.1016/j.toxlet.2011.06.004. Epub 2011 Jun 21.
The aim of the present study was to examine the effect of TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) injected at the early stage of incubation on hormonal activity of the chicken ovary and testis during the second half of embryogenesis measured by steroid concentrations in blood plasma and gonads. The effect of TCDD on hatchability was also evaluated. In the first experiment TCDD was administrated to chicken eggs on day 7 of embryogenesis (E7) at doses of 0 (control), 2.5, 5 and 10ng/egg dissolved in 50μl of peanut oil. Blood plasma for estradiol (E2) and testosterone (T) determination was collected from embryos at E14, E18, E20 and at hatching (D1). In the second experiment TCDD at doses of 0 (control), 2.5, 5 and 10ng/egg dissolved in 50μl of DMSO was injected on E6. Blood plasma and gonads were collected on the day of hatching for progesterone (P4), T and E2 concentrations measured by means of the RIA method. It was found that TCDD injection: (1) increased the level of T and decreased the level of E2 in the plasma of female chicken embryos during the second half of embryogenesis, while on the other hand in male embryos the effect of TCDD was opposite, (2) increased T and E2 concentrations in plasma of newly hatched female chickens with a concomitant decrease of these hormones in the ovary; P4 in the ovary was elevated by TCDD, (3) decreased P4 and T in plasma and testes, whereas increased E2 concentration in the plasma of newly hatched male embryos (E2 concentration in the testes was below the sensitivity of the applied RIA method), and (4) decreased hatchability at all examined doses. The results obtained clearly demonstrate that exposure to TCDD at an early stage of embryogenesis affects steroid production and secretion by chicken gonads. The effect of TCDD depends on (1) the applied dose, (2) the day of embryogenesis, and (3) the sex. It is suggested that dioxins are potent modulators of the process of steroidogenesis in the chicken gonads. Moreover, the data obtained indicate that dioxins exert an effect on embryo development and the hatching process.
本研究旨在探讨在胚胎发育的早期阶段注射 TCDD（2,3,7,8-四氯二苯并对二恶英）对鸡卵巢和睾丸在胚胎发生后半期的激素活性的影响，这是通过测量血浆和性腺中的类固醇浓度来评估的。还评估了 TCDD 对孵化率的影响。在第一个实验中，在胚胎发生第 7 天（E7）向鸡卵中注射 TCDD，剂量为 0（对照）、2.5、5 和 10ng/卵，溶于 50μl 花生油中。在 E14、E18、E20 和孵化时（D1）从胚胎中采集用于测定雌二醇（E2）和睾酮（T）的血浆。在第二个实验中，将 TCDD 以 0（对照）、2.5、5 和 10ng/卵溶于 50μl DMSO 的剂量在 E6 时注射。在孵化当天采集血浆和性腺，通过 RIA 法测定孕激素（P4）、T 和 E2 浓度。结果发现，TCDD 注射：（1）增加了雌性鸡胚胎在胚胎发生后半期的血浆中 T 和降低了 E2 的水平，而另一方面在雄性胚胎中 TCDD 的作用相反；（2）增加了刚孵化的雌性小鸡血浆中的 T 和 E2 浓度，同时降低了卵巢中的这些激素；TCDD 使卵巢中的 P4 升高；（3）降低了刚孵化的雄性胚胎血浆和睾丸中的 P4 和 T，而增加了 E2 浓度；（4）降低了所有检查剂量下的孵化率。结果清楚地表明，在胚胎发生的早期阶段暴露于 TCDD 会影响鸡性腺的类固醇产生和分泌。TCDD 的作用取决于（1）所使用的剂量；（2）胚胎发育的天数；（3）性别。提示二恶英是鸡性腺中类固醇生成过程的有效调节剂。此外，所得数据表明二恶英对胚胎发育和孵化过程有影响。
