Effects Of Zearalenone-Diet On Expression Of GHR,Ghrelin And PCNA In Ovaries Of Post-Weaning Piglets

Zearalenone(ZEN) is commonly found on several foods and feeds in the temperate regions and effect reproductive functions. Numerous reports have shown ZEN can increase the weight of genital organs. Growth hormone(GH) could control ovarian follicular development and GHR was GH special binding local sites. Ghrelin has been implicated in the control of cells in reproductive tissues. Meanwhile, ghrelin could regulate the secretion of GH. The proliferating cell nuclear antigen(PCNA) is an effective index of cell proliferation. The present study investigates effects of a ZEN-contaminated diet on the development of ovaries in post-weaning piglets by the detection of GHR, ghrelin and PCNA protein and relative abundance of mRNA. A total of twenty piglets(Duroc × Landrace × Yorkshire) weaned at 28 d, with an average body weight of 8.74 ± 0.26 kg(P = 0.919) were used in this study. Piglets in the control group(n = 10) were fed a normal basal diet, and that in the treatment group(n = 10) were fed a ZEN-contaminated diet(1.04 mg/kg) for 35 d, then euthanized piglets, collected ovaries. Results were followed: 1.04 mg/kg ZEN was no significant impact on average daily gain(P = 0.708), average daily feed intake(P = 0.861) and gain/feed(P = 0.838), but it caused vulva swelling and increased the weight of relative genital organ. The proportion of growing follicles(P < 0.001) and diameter of the largest growing follicle in ovaries(P < 0.001) were greater in piglets fed the diet with ZEN. The total integrated optical density of immunoreactivity(GHR: P = 0.017; ghrelin: P = 0.003; PCNA: P < 0.001) and mRNA expression(GHR: P=0.021; ghrelin: P = 0.019; PCNA: P = 0.002) increased significantly following the ZEN-contaminated diet. In addition, the expression of ghrelin immunoreactivity was similar to GHR immunoreactivity which were detected in oocytes of ovarian follicles at all developmental stages(primordial and growing follicles), as well as in granulosa cells of growing follicles. The staining of GHR immunoreactivity and ghrelin immunoreactivity in healthy follicles were weak, and it became stronger when follicles were atretic. In atretic growing follicles, the staining of granulosa cell was stronger as atretia progressed. But, GHR immunoreactivities were detected in vascular smooth muscle cells of ovary. The expressions of GHR and ghrelin protein were varied from the status of follicular development. The IOD of GHR immunoreactivity and ghrelin immunoreactivity in single atretic primordial / growing follicles were significantly higher than that in healthy. PCNA immunoreactivities were detected in oocytes and granulosa cells of all kinds of follicles in ovary. The intensity of PCNA immunoreactivity and the number of PCNA immunoreactive positive cells(granulosa cells or theca cells) of atretic follicles correlated to the degree of follicular atresia: the higher the degree of atresia, the lower the number of PCNA immunoreactive granulosa cells which was obviously also accompanied by weaker staining. Whereas, theca cells with PCNA immunoreactivity showed a clear increase in number. This phenomenon was marked in the cells of growing follicles in the treatment group, and revealed that ZEN could stimulate the proliferation of oocytes, granulosa cells, and even theca cells. The IOD of PCNA immunoreactivity in single atretic primordial follicle was lower than that in the healthy primordial follicle. In the treatment group, single IOD of PCNA immunoreactivity in the healthy growing follicle was higher than that in atretic growing follicle, but there was no difference in the control group. These findings hint that 1.04 mg/kg ZEN couldn't affect the growth performances of post-weaning piglets, but it could increase the relative genital organ weight and accelerate the follicle(ovary) development, possibly due, in part, to altering the expression of GHR, ghrelin and PCNA. A diet supplemented with a small amount of ZEN can accelerate the development of ovarian follicles in post-weaning piglets which could lead to subsequent reproductive disorders.