Zhou Min, Yang Li Jie, Yang Wei Ren, Huang Li Bo, Zhou Xue Mei, Jiang Shu Zhen, Yang Zai Bin
Department of Animal Sciences and Technology and Shandong Provincial Key Laboratory of Animal Biotechnology and Disease Control and Prevention, Shandong Agricultural University, Taian, Shandong 271018, China.
Asian-Australas J Anim Sci. 2018 Jan;31(1):32-39. doi: 10.5713/ajas.17.0526. Epub 2017 Sep 18.
In this study, we investigated the adverse effects of dietary zearalenone (ZEA) (0.5 to 1.5 mg/kg diet) on the localization and expression of the growth hormone receptor (GHR) in the uteri of post-weaning gilts and explored alternative mechanism of the reproductive toxicity of ZEA on piglets.
A total of forty healthy piglets (Duroc×Landrace×Large White) aged 28 d were selected for study. Piglets were transferred to single cages after 10 days' adaptation on an obstetric table. The animals were allocated to one of four treatments: a normal basal diet supplemented with 0 (Control), 0.5 (ZEA0.5), 1.0 (ZEA1.0), or 1.5 (ZEA1.5) mg/kg purified ZEA, and fed for 35 d after the 10-d adaptation. Analyzed ZEA concentrations in the diets were 0, 0.52±0.07, 1.04±0.03, and 1.51±0.13 mg/kg, respectively. At the end of the feeding trial, piglets were euthanized after being fasted for 12 h. Two samples of uterine tissue from each pig were rapidly collected, one of which was stored at -80°C for analysis of the relative mRNA and protein expression of GHR, and the second was promptly fixed in Bouin's solution for immunohistochemical analysis.
The relative weight of the uteri and thickness of the myometrium and endometrium increased linearly (p<0.001) and quadratically (p<0.001) with an increasing level of ZEA. The results of immunohistochemical analysis indicated that GHR immunoreactive substance was mainly localizated in the cytoplasm of uterine smooth muscle, glandular epithelial, luminal epithelial, stromal, and vascular endothelial cells. In contrast, nuclear staining was rarely observed. The immunoreactive integrated optic density of GHR in the myometrium, luminal epithelium, glandular epithelium, and whole uteri of weaning gilts increased linearly (p<0.001) and quadratically (p<0.05) with an increasing level of ZEA. The mRNA and protein expression of GHR in the uteri of weaning gilts increased linearly (p<0.001) and quadratically (p<0.05) with an increasing level of ZEA.
In conclusion, ZEA at a concentration of 0.5 mg/kg was sufficient to significantly thicken the myometrium and endometrium, and at a concentration of 1.0 mg/kg induced a high level of GHR expression to promote growth and development of the uteri. This revealed an alternative molecular mechanism whereby ZEA induces growth and development of the uteri and provides a theoretical basis for the revision of Chinese feed hygiene standards.
在本研究中，我们调查了日粮中玉米赤霉烯酮（ZEA）（0.5至1.5毫克/千克日粮）对断奶后小母猪子宫中生长激素受体（GHR）定位和表达的不良影响，并探讨ZEA对仔猪生殖毒性的替代机制。
总共选择40头28日龄健康仔猪（杜洛克×长白×大白）进行研究。仔猪在产科手术台上适应10天后转移到单笼中。将动物分为四种处理之一：补充0（对照）、0.5（ZEA0.5）、1.0（ZEA1.0）或1.5（ZEA1.5）毫克/千克纯化ZEA的正常基础日粮，并在10天适应期后饲喂35天。日粮中分析的ZEA浓度分别为0、0.52±0.07、1.04±0.03和1.51±0.13毫克/千克。在饲养试验结束时，仔猪禁食12小时后安乐死。从每头猪中快速采集两份子宫组织样本，其中一份保存在-80°C用于分析GHR的相对mRNA和蛋白表达，另一份立即固定在Bouin氏溶液中用于免疫组织化学分析。
随着ZEA水平的升高，子宫相对重量、肌层和子宫内膜厚度呈线性（p<0.001）和二次方（p<0.001）增加。免疫组织化学分析结果表明，GHR免疫反应物质主要定位于子宫平滑肌、腺上皮、腔上皮、基质和血管内皮细胞的细胞质中。相比之下，很少观察到细胞核染色。断奶后小母猪肌层、腔上皮、腺上皮和整个子宫中GHR的免疫反应积分光密度随着ZEA水平的升高呈线性（p<0.001）和二次方（p<0.05）增加。断奶后小母猪子宫中GHR的mRNA和蛋白表达随着ZEA水平的升高呈线性（p<0.001）和二次方（p<0.05）增加。
总之，浓度为0.5毫克/千克的ZEA足以显著增厚肌层和子宫内膜，浓度为1.0毫克/千克时可诱导高水平的GHR表达以促进子宫生长发育。这揭示了ZEA诱导子宫生长发育的一种替代分子机制，并为修订中国饲料卫生标准提供了理论依据。
