Abstract
Zearalenone (ZEA) has an estrogen-like effect, which can injure the reproductive system of animals, causing infertility, and abortion in sows. However, the underlying mechanisms are still not clear. The objective of this study was to assess the effects of ZEA on the localization and expression of growth hormone (GH), growth hormone receptor (GHR), and heat shock protein 70 (Hsp70) in the ovaries of post-weaning gilts. Forty healthy post-weaning gilts were randomly provided one of four diets: normal basal diet supplemented with 0 (control), 0.5 (ZEA0.5), 1.0 (ZEA1.0), and 1.5 (ZEA1.5) mg ZEA/kg. Gilts were housed and fed individually for 35 days; the ovaries were collected after euthanasia for antioxidant index, relative mRNA and protein expression, and immunohistochemical analyses of GH, GHR, and Hsp70. The results revealed that the glutathione peroxidase and total superoxide dismutase levels decreased (p < 0.05), whereas the malondialdehyde level increased (p < 0.05) with increasing ZEA content. The localization pattern of GH, GHR, and Hsp70 in ZEA-treated gilts was the same as that in the control; however, the localization of yellow and brown immunoreactive substances of GH, GHR, and Hsp70 was stronger in the ZEA groups than in the control. The relative mRNA and protein expression of GHR and Hsp70 was the highest in the ZEA1.0 group (p < 0.05), whereas that of GH was the highest in the ZEA0.5 group (p < 0.05). The mRNA and protein expression of GH was lower in the ZEA1.5 group than in the control (p < 0.05). Hsp70 results showed adverse responses to increasing ZEA levels in gilt ovaries, suggesting that Hsp70 played an important role in alleviating ZEA-induced oxidative stress.
Highlights
Zearalenone (ZEA; F-2 toxin), an estrogenic mycotoxin mainly produced by Fusarium fungi [1], is common in cereals, such as corn, barley, sorghum, rye, and wheat [2], and often found in processed products [3,4,5]
Macroscopic primary growth follicles were observed in the ZEA0.5 group, and a large number of secondary growth follicles were observed in the ZEA1.0 group; follicular atresia was observed in the ZEA1.5 group
Compared with the other groups, the ovarian weight was heaviest in the ZEA1.0 group (Table 3); the ovarian weight of the ZEA1.5 group was significantly higher than that of the ZEA0.5 group and the control (p < 0.05), which was consistent with the visual results
Summary
Zearalenone (ZEA; F-2 toxin), an estrogenic mycotoxin mainly produced by Fusarium fungi [1], is common in cereals, such as corn, barley, sorghum, rye, and wheat [2], and often found in processed products [3,4,5]. Our previous studies have shown that ZEA (1.05 mg ZEA/kg) induces deleterious effects on genital organs, serum hormones, and oxidative stress in post-weaning piglets in a genderdependent manner [15, 16]. ZEA at concentrations of 1.1–3.2 mg ZEA/kg linearly increases vulva size and genital organ weights, decreases the antioxidant capacity of the liver and serum [17], alters the structure of the uteri and ovaries, and promotes follicle growth by modulating the Wnt/β-catenin signaling pathway and estrogen-receptor gene expression in the ovaries of post-weaning gilts [18]; the effect of ZEA on the distribution and expression of growth hormone (GH), GH receptor (GHR), and heat shock protein 70 (Hsp70) in the ovaries has not yet been fully elucidated. Several studies have reported the distribution or expression of GHR in the uteri of rats [22] and sheep [21] as well as in the ovaries of humans and chicken [23, 24]; to date, no study has examined the expression of GHR in the ovaries of gilts challenged by ZEA
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