不同饲喂水平对绵羊睾丸发育、睾酮合成相关基因及雄激素受体(AR)表达的影响

旨在研究不同饲喂水平对绵羊睾丸发育、睾酮（T）合成相关基因与雄激素受体（androgen receptor， AR）表达的影响。本研究采用单因素完全随机试验设计，将18只健康、体重相近（（35±0.5） kg）的杜泊羊（♂）×晋中绵羊（♀）杂F1代4月龄公羔随机分为3组，每组6只，分别按照自由采食（AL组）、自由采食量的65%（AL65组）和自由采食量的40%（AL40组）3个水平进行饲喂。当AL组任意1只羔羊体重达到50 kg时全部屠宰，测定睾丸的周径与长度后采集睾丸组织，通过苏木精-伊红（hematoxylin-eosin，H-E）染色观察曲精细管生精上皮结构；酶联免疫（enzyme linked immunosorbent assay，ELISA）法测定睾酮（testosterone，T）的水平；用定量PCR（quantitative real-time PCR，qRT-PCR）检测T合成相关基因和AR mRNA的表达情况；通过免疫组化和Western blotting的方法对绵羊睾丸组织中的AR进行定位与定量分析。结果表明，AL40组羔羊睾丸周径和长度显著低于AL组（P<0.05），但与AL65组差异不显著（P>0.05）；AL40组曲精细管生精上皮厚度与AL65组差异不显著（P>0.05），但均显著低于AL组（P<0.05）。随着饲喂水平的提高，生精细胞和间质细胞密度显著增加（P<0.05），T水平和STAR、3β-HSD基因以及AR mRNA和蛋白表达量均显著提高（P<0.05）；睾丸间质细胞、初级精母细胞、精子细胞、管壁肌样细胞层和间质血管平滑肌细胞中均观察到AR阳性产物。综上所述，绵羊的睾丸发育、T含量、T合成相关基因和AR的表达均受到日粮营养水平的调控。日粮营养水平可能通过改变T水平和生精细胞对T的敏感性来调控精子发生过程，从而影响其性成熟和繁殖性能。

Effects of Different Feeding Levels on Testis Development and the Expression of Steroidogenesis-Related Genes and Androgen Receptor (AR) in Sheep

The objective of this study was to investigate the effects of different feeding levels on testicular development, testosterone (T) concentration, the expression of testosterone synthesis-related genes and androgen receptor (AR) in testis of sheep. Eighteen healthy 4-month-old Dorper×Jinzhong crossed F1 ram lambs with similar body weight of ((35±0.5) kg) were selected and randomly divided into 3 groups for a comparative slaughter trial. They were offered one type of feed at 100%(AL group), 65%(AL65 group) and 40%(AL40 group) of ad libitum intake, respectively. When any lamb in AL group reached a body weight of 50 kg, all animals were slaughtered. After the testicular circumference and length were examined, tissue samples were collected for analyzing testosterone concentration and histological parameters using ELISA and H-E staining method, respectively. The expression of testosterone synthesis-related genes and AR mRNA were detected using quantitative real-time PCR. Localization and quantification of AR in testis of lambs were determined by immunohistochemistry and Western blotting analysis. The results showed that the length and circumference of testis in the AL40 group were significantly lower than those in the AL group(P<0.05), no significant difference was observed between the AL40 and AL65 groups(P>0.05). The thickness of germinal epithelium of lambs in AL40 group was not significantly different from that in AL65 group, but both were significantly lower than that in AL group (P<0.05). The density of spermatogenic cells and leydig cells were remarkably increased with the increasing feeding levels(P<0.05). Testosterone concentration, the expression of STAR, 3β-HSD and AR genes and AR protein were also significantly increased(P<0.05). Immunopositive product of AR was detected in leydig cells,primary spermatocytes, spermatids, peritubular myoid cells and perivascular smooth muscle cells. In conclusion, the testicular development, T level, the expression of testosterone synthesis-related genes and AR were regulated by dietary nutrition level. Dietary nutrition could modulate the process of spermatogenesis by regulating T concentration and the sensitivity of spermatogenic cells to T, which could influence the sexual maturation and reproductive performance of male animals.